external/cli11/CLI11.hpp

// CLI11: Version 2.0.0
// Originally designed by Henry Schreiner
// https://github.com/CLIUtils/CLI11
//
// This is a standalone header file generated by MakeSingleHeader.py in CLI11/scripts
// from: v2.0.0 (added include gaurd)
//
// CLI11 2.0.0 Copyright (c) 2017-2020 University of Cincinnati, developed by Henry
// Schreiner under NSF AWARD 1414736. All rights reserved.
//
// Redistribution and use in source and binary forms of CLI11, with or without
// modification, are permitted provided that the following conditions are met:
//
// 1. Redistributions of source code must retain the above copyright notice, this
//    list of conditions and the following disclaimer.
// 2. Redistributions in binary form must reproduce the above copyright notice,
//    this list of conditions and the following disclaimer in the documentation
//    and/or other materials provided with the distribution.
// 3. Neither the name of the copyright holder nor the names of its contributors
//    may be used to endorse or promote products derived from this software without
//    specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
// WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
// ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
// (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
// LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
// ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

#pragma once

// Standard combined includes:
#include <memory>
#include <string>
#include <functional>
#include <vector>
#include <exception>
#include <sstream>
#include <cstdint>
#include <utility>
#include <iomanip>
#include <iterator>
#include <algorithm>
#include <tuple>
#include <stdexcept>
#include <iostream>
#include <fstream>
#include <locale>
#include <type_traits>
#include <map>
#include <limits>
#include <numeric>
#include <cmath>
#include <set>


#define CLI11_VERSION_MAJOR 2
#define CLI11_VERSION_MINOR 0
#define CLI11_VERSION_PATCH 0
#define CLI11_VERSION "2.0.0"


// The following version macro is very similar to the one in pybind11
#if !(defined(_MSC_VER) && __cplusplus == 199711L) && !defined(__INTEL_COMPILER)
#if __cplusplus >= 201402L
#define CLI11_CPP14
#if __cplusplus >= 201703L
#define CLI11_CPP17
#if __cplusplus > 201703L
#define CLI11_CPP20
#endif
#endif
#endif
#elif defined(_MSC_VER) && __cplusplus == 199711L
// MSVC sets _MSVC_LANG rather than __cplusplus (supposedly until the standard is fully implemented)
// Unless you use the /Zc:__cplusplus flag on Visual Studio 2017 15.7 Preview 3 or newer
#if _MSVC_LANG >= 201402L
#define CLI11_CPP14
#if _MSVC_LANG > 201402L && _MSC_VER >= 1910
#define CLI11_CPP17
#if __MSVC_LANG > 201703L && _MSC_VER >= 1910
#define CLI11_CPP20
#endif
#endif
#endif
#endif

#if defined(CLI11_CPP14)
#define CLI11_DEPRECATED(reason) [[deprecated(reason)]]
#elif defined(_MSC_VER)
#define CLI11_DEPRECATED(reason) __declspec(deprecated(reason))
#else
#define CLI11_DEPRECATED(reason) __attribute__((deprecated(reason)))
#endif


// C standard library
// Only needed for existence checking
#if defined CLI11_CPP17 && defined __has_include && !defined CLI11_HAS_FILESYSTEM
#if __has_include(<filesystem>)
// Filesystem cannot be used if targeting macOS < 10.15
#if defined __MAC_OS_X_VERSION_MIN_REQUIRED && __MAC_OS_X_VERSION_MIN_REQUIRED < 101500
#define CLI11_HAS_FILESYSTEM 0
#else
#include <filesystem>
#if defined __cpp_lib_filesystem && __cpp_lib_filesystem >= 201703
#if defined _GLIBCXX_RELEASE && _GLIBCXX_RELEASE >= 9
#define CLI11_HAS_FILESYSTEM 1
#elif defined(__GLIBCXX__)
// if we are using gcc and Version <9 default to no filesystem
#define CLI11_HAS_FILESYSTEM 0
#else
#define CLI11_HAS_FILESYSTEM 1
#endif
#else
#define CLI11_HAS_FILESYSTEM 0
#endif
#endif
#endif
#endif

#if defined CLI11_HAS_FILESYSTEM && CLI11_HAS_FILESYSTEM > 0
#include <filesystem>  // NOLINT(build/include)
#else
#include <sys/stat.h>
#include <sys/types.h>
#endif


namespace CLI {


/// Include the items in this namespace to get free conversion of enums to/from streams.
/// (This is available inside CLI as well, so CLI11 will use this without a using statement).
namespace enums {

/// output streaming for enumerations
template <typename T, typename = typename std::enable_if<std::is_enum<T>::value>::type>
std::ostream &operator<<(std::ostream &in, const T &item) {
    // make sure this is out of the detail namespace otherwise it won't be found when needed
    return in << static_cast<typename std::underlying_type<T>::type>(item);
}

}  // namespace enums

/// Export to CLI namespace
using enums::operator<<;

namespace detail {
/// a constant defining an expected max vector size defined to be a big number that could be multiplied by 4 and not
/// produce overflow for some expected uses
constexpr int expected_max_vector_size{1 << 29};
// Based on http://stackoverflow.com/questions/236129/split-a-string-in-c
/// Split a string by a delim
inline std::vector<std::string> split(const std::string &s, char delim) {
    std::vector<std::string> elems;
    // Check to see if empty string, give consistent result
    if(s.empty()) {
        elems.emplace_back();
    } else {
        std::stringstream ss;
        ss.str(s);
        std::string item;
        while(std::getline(ss, item, delim)) {
            elems.push_back(item);
        }
    }
    return elems;
}

/// Simple function to join a string
template <typename T> std::string join(const T &v, std::string delim = ",") {
    std::ostringstream s;
    auto beg = std::begin(v);
    auto end = std::end(v);
    if(beg != end)
        s << *beg++;
    while(beg != end) {
        s << delim << *beg++;
    }
    return s.str();
}

/// Simple function to join a string from processed elements
template <typename T,
          typename Callable,
          typename = typename std::enable_if<!std::is_constructible<std::string, Callable>::value>::type>
std::string join(const T &v, Callable func, std::string delim = ",") {
    std::ostringstream s;
    auto beg = std::begin(v);
    auto end = std::end(v);
    auto loc = s.tellp();
    while(beg != end) {
        auto nloc = s.tellp();
        if(nloc > loc) {
            s << delim;
            loc = nloc;
        }
        s << func(*beg++);
    }
    return s.str();
}

/// Join a string in reverse order
template <typename T> std::string rjoin(const T &v, std::string delim = ",") {
    std::ostringstream s;
    for(std::size_t start = 0; start < v.size(); start++) {
        if(start > 0)
            s << delim;
        s << v[v.size() - start - 1];
    }
    return s.str();
}

// Based roughly on http://stackoverflow.com/questions/25829143/c-trim-whitespace-from-a-string

/// Trim whitespace from left of string
inline std::string &ltrim(std::string &str) {
    auto it = std::find_if(str.begin(), str.end(), [](char ch) { return !std::isspace<char>(ch, std::locale()); });
    str.erase(str.begin(), it);
    return str;
}

/// Trim anything from left of string
inline std::string &ltrim(std::string &str, const std::string &filter) {
    auto it = std::find_if(str.begin(), str.end(), [&filter](char ch) { return filter.find(ch) == std::string::npos; });
    str.erase(str.begin(), it);
    return str;
}

/// Trim whitespace from right of string
inline std::string &rtrim(std::string &str) {
    auto it = std::find_if(str.rbegin(), str.rend(), [](char ch) { return !std::isspace<char>(ch, std::locale()); });
    str.erase(it.base(), str.end());
    return str;
}

/// Trim anything from right of string
inline std::string &rtrim(std::string &str, const std::string &filter) {
    auto it =
        std::find_if(str.rbegin(), str.rend(), [&filter](char ch) { return filter.find(ch) == std::string::npos; });
    str.erase(it.base(), str.end());
    return str;
}

/// Trim whitespace from string
inline std::string &trim(std::string &str) { return ltrim(rtrim(str)); }

/// Trim anything from string
inline std::string &trim(std::string &str, const std::string filter) { return ltrim(rtrim(str, filter), filter); }

/// Make a copy of the string and then trim it
inline std::string trim_copy(const std::string &str) {
    std::string s = str;
    return trim(s);
}

/// remove quotes at the front and back of a string either '"' or '\''
inline std::string &remove_quotes(std::string &str) {
    if(str.length() > 1 && (str.front() == '"' || str.front() == '\'')) {
        if(str.front() == str.back()) {
            str.pop_back();
            str.erase(str.begin(), str.begin() + 1);
        }
    }
    return str;
}

/// Make a copy of the string and then trim it, any filter string can be used (any char in string is filtered)
inline std::string trim_copy(const std::string &str, const std::string &filter) {
    std::string s = str;
    return trim(s, filter);
}
/// Print a two part "help" string
inline std::ostream &format_help(std::ostream &out, std::string name, const std::string &description, std::size_t wid) {
    name = "  " + name;
    out << std::setw(static_cast<int>(wid)) << std::left << name;
    if(!description.empty()) {
        if(name.length() >= wid)
            out << "\n" << std::setw(static_cast<int>(wid)) << "";
        for(const char c : description) {
            out.put(c);
            if(c == '\n') {
                out << std::setw(static_cast<int>(wid)) << "";
            }
        }
    }
    out << "\n";
    return out;
}

/// Print subcommand aliases
inline std::ostream &format_aliases(std::ostream &out, const std::vector<std::string> &aliases, std::size_t wid) {
    if(!aliases.empty()) {
        out << std::setw(static_cast<int>(wid)) << "     aliases: ";
        bool front = true;
        for(const auto &alias : aliases) {
            if(!front) {
                out << ", ";
            } else {
                front = false;
            }
            out << alias;
        }
        out << "\n";
    }
    return out;
}

/// Verify the first character of an option
template <typename T> bool valid_first_char(T c) {
    return std::isalnum(c, std::locale()) || c == '_' || c == '?' || c == '@';
}

/// Verify following characters of an option
template <typename T> bool valid_later_char(T c) { return valid_first_char(c) || c == '.' || c == '-'; }

/// Verify an option name
inline bool valid_name_string(const std::string &str) {
    if(str.empty() || !valid_first_char(str[0]))
        return false;
    for(auto c : str.substr(1))
        if(!valid_later_char(c))
            return false;
    return true;
}

/// check if a string is a container segment separator (empty or "%%")
inline bool is_separator(const std::string &str) {
    static const std::string sep("%%");
    return (str.empty() || str == sep);
}

/// Verify that str consists of letters only
inline bool isalpha(const std::string &str) {
    return std::all_of(str.begin(), str.end(), [](char c) { return std::isalpha(c, std::locale()); });
}

/// Return a lower case version of a string
inline std::string to_lower(std::string str) {
    std::transform(std::begin(str), std::end(str), std::begin(str), [](const std::string::value_type &x) {
        return std::tolower(x, std::locale());
    });
    return str;
}

/// remove underscores from a string
inline std::string remove_underscore(std::string str) {
    str.erase(std::remove(std::begin(str), std::end(str), '_'), std::end(str));
    return str;
}

/// Find and replace a substring with another substring
inline std::string find_and_replace(std::string str, std::string from, std::string to) {

    std::size_t start_pos = 0;

    while((start_pos = str.find(from, start_pos)) != std::string::npos) {
        str.replace(start_pos, from.length(), to);
        start_pos += to.length();
    }

    return str;
}

/// check if the flag definitions has possible false flags
inline bool has_default_flag_values(const std::string &flags) {
    return (flags.find_first_of("{!") != std::string::npos);
}

inline void remove_default_flag_values(std::string &flags) {
    auto loc = flags.find_first_of('{');
    while(loc != std::string::npos) {
        auto finish = flags.find_first_of("},", loc + 1);
        if((finish != std::string::npos) && (flags[finish] == '}')) {
            flags.erase(flags.begin() + static_cast<std::ptrdiff_t>(loc),
                        flags.begin() + static_cast<std::ptrdiff_t>(finish) + 1);
        }
        loc = flags.find_first_of('{', loc + 1);
    }
    flags.erase(std::remove(flags.begin(), flags.end(), '!'), flags.end());
}

/// Check if a string is a member of a list of strings and optionally ignore case or ignore underscores
inline std::ptrdiff_t find_member(std::string name,
                                  const std::vector<std::string> names,
                                  bool ignore_case = false,
                                  bool ignore_underscore = false) {
    auto it = std::end(names);
    if(ignore_case) {
        if(ignore_underscore) {
            name = detail::to_lower(detail::remove_underscore(name));
            it = std::find_if(std::begin(names), std::end(names), [&name](std::string local_name) {
                return detail::to_lower(detail::remove_underscore(local_name)) == name;
            });
        } else {
            name = detail::to_lower(name);
            it = std::find_if(std::begin(names), std::end(names), [&name](std::string local_name) {
                return detail::to_lower(local_name) == name;
            });
        }

    } else if(ignore_underscore) {
        name = detail::remove_underscore(name);
        it = std::find_if(std::begin(names), std::end(names), [&name](std::string local_name) {
            return detail::remove_underscore(local_name) == name;
        });
    } else {
        it = std::find(std::begin(names), std::end(names), name);
    }

    return (it != std::end(names)) ? (it - std::begin(names)) : (-1);
}

/// Find a trigger string and call a modify callable function that takes the current string and starting position of the
/// trigger and returns the position in the string to search for the next trigger string
template <typename Callable> inline std::string find_and_modify(std::string str, std::string trigger, Callable modify) {
    std::size_t start_pos = 0;
    while((start_pos = str.find(trigger, start_pos)) != std::string::npos) {
        start_pos = modify(str, start_pos);
    }
    return str;
}

/// Split a string '"one two" "three"' into 'one two', 'three'
/// Quote characters can be ` ' or "
inline std::vector<std::string> split_up(std::string str, char delimiter = '\0') {

    const std::string delims("\'\"`");
    auto find_ws = [delimiter](char ch) {
        return (delimiter == '\0') ? (std::isspace<char>(ch, std::locale()) != 0) : (ch == delimiter);
    };
    trim(str);

    std::vector<std::string> output;
    bool embeddedQuote = false;
    char keyChar = ' ';
    while(!str.empty()) {
        if(delims.find_first_of(str[0]) != std::string::npos) {
            keyChar = str[0];
            auto end = str.find_first_of(keyChar, 1);
            while((end != std::string::npos) && (str[end - 1] == '\\')) {  // deal with escaped quotes
                end = str.find_first_of(keyChar, end + 1);
                embeddedQuote = true;
            }
            if(end != std::string::npos) {
                output.push_back(str.substr(1, end - 1));
                if(end + 2 < str.size()) {
                    str = str.substr(end + 2);
                } else {
                    str.clear();
                }

            } else {
                output.push_back(str.substr(1));
                str = "";
            }
        } else {
            auto it = std::find_if(std::begin(str), std::end(str), find_ws);
            if(it != std::end(str)) {
                std::string value = std::string(str.begin(), it);
                output.push_back(value);
                str = std::string(it + 1, str.end());
            } else {
                output.push_back(str);
                str = "";
            }
        }
        // transform any embedded quotes into the regular character
        if(embeddedQuote) {
            output.back() = find_and_replace(output.back(), std::string("\\") + keyChar, std::string(1, keyChar));
            embeddedQuote = false;
        }
        trim(str);
    }
    return output;
}

/// Add a leader to the beginning of all new lines (nothing is added
/// at the start of the first line). `"; "` would be for ini files
///
/// Can't use Regex, or this would be a subs.
inline std::string fix_newlines(const std::string &leader, std::string input) {
    std::string::size_type n = 0;
    while(n != std::string::npos && n < input.size()) {
        n = input.find('\n', n);
        if(n != std::string::npos) {
            input = input.substr(0, n + 1) + leader + input.substr(n + 1);
            n += leader.size();
        }
    }
    return input;
}

/// This function detects an equal or colon followed by an escaped quote after an argument
/// then modifies the string to replace the equality with a space.  This is needed
/// to allow the split up function to work properly and is intended to be used with the find_and_modify function
/// the return value is the offset+1 which is required by the find_and_modify function.
inline std::size_t escape_detect(std::string &str, std::size_t offset) {
    auto next = str[offset + 1];
    if((next == '\"') || (next == '\'') || (next == '`')) {
        auto astart = str.find_last_of("-/ \"\'`", offset - 1);
        if(astart != std::string::npos) {
            if(str[astart] == ((str[offset] == '=') ? '-' : '/'))
                str[offset] = ' ';  // interpret this as a space so the split_up works properly
        }
    }
    return offset + 1;
}

/// Add quotes if the string contains spaces
inline std::string &add_quotes_if_needed(std::string &str) {
    if((str.front() != '"' && str.front() != '\'') || str.front() != str.back()) {
        char quote = str.find('"') < str.find('\'') ? '\'' : '"';
        if(str.find(' ') != std::string::npos) {
            str.insert(0, 1, quote);
            str.append(1, quote);
        }
    }
    return str;
}

}  // namespace detail


// Use one of these on all error classes.
// These are temporary and are undef'd at the end of this file.
#define CLI11_ERROR_DEF(parent, name)                                                                                  \
  protected:                                                                                                           \
    name(std::string ename, std::string msg, int exit_code) : parent(std::move(ename), std::move(msg), exit_code) {}   \
    name(std::string ename, std::string msg, ExitCodes exit_code)                                                      \
        : parent(std::move(ename), std::move(msg), exit_code) {}                                                       \
                                                                                                                       \
  public:                                                                                                              \
    name(std::string msg, ExitCodes exit_code) : parent(#name, std::move(msg), exit_code) {}                           \
    name(std::string msg, int exit_code) : parent(#name, std::move(msg), exit_code) {}

// This is added after the one above if a class is used directly and builds its own message
#define CLI11_ERROR_SIMPLE(name)                                                                                       \
    explicit name(std::string msg) : name(#name, msg, ExitCodes::name) {}

/// These codes are part of every error in CLI. They can be obtained from e using e.exit_code or as a quick shortcut,
/// int values from e.get_error_code().
enum class ExitCodes {
    Success = 0,
    IncorrectConstruction = 100,
    BadNameString,
    OptionAlreadyAdded,
    FileError,
    ConversionError,
    ValidationError,
    RequiredError,
    RequiresError,
    ExcludesError,
    ExtrasError,
    ConfigError,
    InvalidError,
    HorribleError,
    OptionNotFound,
    ArgumentMismatch,
    BaseClass = 127
};

// Error definitions

/// @defgroup error_group Errors
/// @brief Errors thrown by CLI11
///
/// These are the errors that can be thrown. Some of them, like CLI::Success, are not really errors.
/// @{

/// All errors derive from this one
class Error : public std::runtime_error {
    int actual_exit_code;
    std::string error_name{"Error"};

  public:
    int get_exit_code() const { return actual_exit_code; }

    std::string get_name() const { return error_name; }

    Error(std::string name, std::string msg, int exit_code = static_cast<int>(ExitCodes::BaseClass))
        : runtime_error(msg), actual_exit_code(exit_code), error_name(std::move(name)) {}

    Error(std::string name, std::string msg, ExitCodes exit_code) : Error(name, msg, static_cast<int>(exit_code)) {}
};

// Note: Using Error::Error constructors does not work on GCC 4.7

/// Construction errors (not in parsing)
class ConstructionError : public Error {
    CLI11_ERROR_DEF(Error, ConstructionError)
};

/// Thrown when an option is set to conflicting values (non-vector and multi args, for example)
class IncorrectConstruction : public ConstructionError {
    CLI11_ERROR_DEF(ConstructionError, IncorrectConstruction)
    CLI11_ERROR_SIMPLE(IncorrectConstruction)
    static IncorrectConstruction PositionalFlag(std::string name) {
        return IncorrectConstruction(name + ": Flags cannot be positional");
    }
    static IncorrectConstruction Set0Opt(std::string name) {
        return IncorrectConstruction(name + ": Cannot set 0 expected, use a flag instead");
    }
    static IncorrectConstruction SetFlag(std::string name) {
        return IncorrectConstruction(name + ": Cannot set an expected number for flags");
    }
    static IncorrectConstruction ChangeNotVector(std::string name) {
        return IncorrectConstruction(name + ": You can only change the expected arguments for vectors");
    }
    static IncorrectConstruction AfterMultiOpt(std::string name) {
        return IncorrectConstruction(
            name + ": You can't change expected arguments after you've changed the multi option policy!");
    }
    static IncorrectConstruction MissingOption(std::string name) {
        return IncorrectConstruction("Option " + name + " is not defined");
    }
    static IncorrectConstruction MultiOptionPolicy(std::string name) {
        return IncorrectConstruction(name + ": multi_option_policy only works for flags and exact value options");
    }
};

/// Thrown on construction of a bad name
class BadNameString : public ConstructionError {
    CLI11_ERROR_DEF(ConstructionError, BadNameString)
    CLI11_ERROR_SIMPLE(BadNameString)
    static BadNameString OneCharName(std::string name) { return BadNameString("Invalid one char name: " + name); }
    static BadNameString BadLongName(std::string name) { return BadNameString("Bad long name: " + name); }
    static BadNameString DashesOnly(std::string name) {
        return BadNameString("Must have a name, not just dashes: " + name);
    }
    static BadNameString MultiPositionalNames(std::string name) {
        return BadNameString("Only one positional name allowed, remove: " + name);
    }
};

/// Thrown when an option already exists
class OptionAlreadyAdded : public ConstructionError {
    CLI11_ERROR_DEF(ConstructionError, OptionAlreadyAdded)
    explicit OptionAlreadyAdded(std::string name)
        : OptionAlreadyAdded(name + " is already added", ExitCodes::OptionAlreadyAdded) {}
    static OptionAlreadyAdded Requires(std::string name, std::string other) {
        return OptionAlreadyAdded(name + " requires " + other, ExitCodes::OptionAlreadyAdded);
    }
    static OptionAlreadyAdded Excludes(std::string name, std::string other) {
        return OptionAlreadyAdded(name + " excludes " + other, ExitCodes::OptionAlreadyAdded);
    }
};

// Parsing errors

/// Anything that can error in Parse
class ParseError : public Error {
    CLI11_ERROR_DEF(Error, ParseError)
};

// Not really "errors"

/// This is a successful completion on parsing, supposed to exit
class Success : public ParseError {
    CLI11_ERROR_DEF(ParseError, Success)
    Success() : Success("Successfully completed, should be caught and quit", ExitCodes::Success) {}
};

/// -h or --help on command line
class CallForHelp : public Success {
    CLI11_ERROR_DEF(Success, CallForHelp)
    CallForHelp() : CallForHelp("This should be caught in your main function, see examples", ExitCodes::Success) {}
};

/// Usually something like --help-all on command line
class CallForAllHelp : public Success {
    CLI11_ERROR_DEF(Success, CallForAllHelp)
    CallForAllHelp()
        : CallForAllHelp("This should be caught in your main function, see examples", ExitCodes::Success) {}
};

/// -v or --version on command line
class CallForVersion : public Success {
    CLI11_ERROR_DEF(Success, CallForVersion)
    CallForVersion()
        : CallForVersion("This should be caught in your main function, see examples", ExitCodes::Success) {}
};

/// Does not output a diagnostic in CLI11_PARSE, but allows main() to return with a specific error code.
class RuntimeError : public ParseError {
    CLI11_ERROR_DEF(ParseError, RuntimeError)
    explicit RuntimeError(int exit_code = 1) : RuntimeError("Runtime error", exit_code) {}
};

/// Thrown when parsing an INI file and it is missing
class FileError : public ParseError {
    CLI11_ERROR_DEF(ParseError, FileError)
    CLI11_ERROR_SIMPLE(FileError)
    static FileError Missing(std::string name) { return FileError(name + " was not readable (missing?)"); }
};

/// Thrown when conversion call back fails, such as when an int fails to coerce to a string
class ConversionError : public ParseError {
    CLI11_ERROR_DEF(ParseError, ConversionError)
    CLI11_ERROR_SIMPLE(ConversionError)
    ConversionError(std::string member, std::string name)
        : ConversionError("The value " + member + " is not an allowed value for " + name) {}
    ConversionError(std::string name, std::vector<std::string> results)
        : ConversionError("Could not convert: " + name + " = " + detail::join(results)) {}
    static ConversionError TooManyInputsFlag(std::string name) {
        return ConversionError(name + ": too many inputs for a flag");
    }
    static ConversionError TrueFalse(std::string name) {
        return ConversionError(name + ": Should be true/false or a number");
    }
};

/// Thrown when validation of results fails
class ValidationError : public ParseError {
    CLI11_ERROR_DEF(ParseError, ValidationError)
    CLI11_ERROR_SIMPLE(ValidationError)
    explicit ValidationError(std::string name, std::string msg) : ValidationError(name + ": " + msg) {}
};

/// Thrown when a required option is missing
class RequiredError : public ParseError {
    CLI11_ERROR_DEF(ParseError, RequiredError)
    explicit RequiredError(std::string name) : RequiredError(name + " is required", ExitCodes::RequiredError) {}
    static RequiredError Subcommand(std::size_t min_subcom) {
        if(min_subcom == 1) {
            return RequiredError("A subcommand");
        }
        return RequiredError("Requires at least " + std::to_string(min_subcom) + " subcommands",
                             ExitCodes::RequiredError);
    }
    static RequiredError
    Option(std::size_t min_option, std::size_t max_option, std::size_t used, const std::string &option_list) {
        if((min_option == 1) && (max_option == 1) && (used == 0))
            return RequiredError("Exactly 1 option from [" + option_list + "]");
        if((min_option == 1) && (max_option == 1) && (used > 1)) {
            return RequiredError("Exactly 1 option from [" + option_list + "] is required and " + std::to_string(used) +
                                     " were given",
                                 ExitCodes::RequiredError);
        }
        if((min_option == 1) && (used == 0))
            return RequiredError("At least 1 option from [" + option_list + "]");
        if(used < min_option) {
            return RequiredError("Requires at least " + std::to_string(min_option) + " options used and only " +
                                     std::to_string(used) + "were given from [" + option_list + "]",
                                 ExitCodes::RequiredError);
        }
        if(max_option == 1)
            return RequiredError("Requires at most 1 options be given from [" + option_list + "]",
                                 ExitCodes::RequiredError);

        return RequiredError("Requires at most " + std::to_string(max_option) + " options be used and " +
                                 std::to_string(used) + "were given from [" + option_list + "]",
                             ExitCodes::RequiredError);
    }
};

/// Thrown when the wrong number of arguments has been received
class ArgumentMismatch : public ParseError {
    CLI11_ERROR_DEF(ParseError, ArgumentMismatch)
    CLI11_ERROR_SIMPLE(ArgumentMismatch)
    ArgumentMismatch(std::string name, int expected, std::size_t received)
        : ArgumentMismatch(expected > 0 ? ("Expected exactly " + std::to_string(expected) + " arguments to " + name +
                                           ", got " + std::to_string(received))
                                        : ("Expected at least " + std::to_string(-expected) + " arguments to " + name +
                                           ", got " + std::to_string(received)),
                           ExitCodes::ArgumentMismatch) {}

    static ArgumentMismatch AtLeast(std::string name, int num, std::size_t received) {
        return ArgumentMismatch(name + ": At least " + std::to_string(num) + " required but received " +
                                std::to_string(received));
    }
    static ArgumentMismatch AtMost(std::string name, int num, std::size_t received) {
        return ArgumentMismatch(name + ": At Most " + std::to_string(num) + " required but received " +
                                std::to_string(received));
    }
    static ArgumentMismatch TypedAtLeast(std::string name, int num, std::string type) {
        return ArgumentMismatch(name + ": " + std::to_string(num) + " required " + type + " missing");
    }
    static ArgumentMismatch FlagOverride(std::string name) {
        return ArgumentMismatch(name + " was given a disallowed flag override");
    }
};

/// Thrown when a requires option is missing
class RequiresError : public ParseError {
    CLI11_ERROR_DEF(ParseError, RequiresError)
    RequiresError(std::string curname, std::string subname)
        : RequiresError(curname + " requires " + subname, ExitCodes::RequiresError) {}
};

/// Thrown when an excludes option is present
class ExcludesError : public ParseError {
    CLI11_ERROR_DEF(ParseError, ExcludesError)
    ExcludesError(std::string curname, std::string subname)
        : ExcludesError(curname + " excludes " + subname, ExitCodes::ExcludesError) {}
};

/// Thrown when too many positionals or options are found
class ExtrasError : public ParseError {
    CLI11_ERROR_DEF(ParseError, ExtrasError)
    explicit ExtrasError(std::vector<std::string> args)
        : ExtrasError((args.size() > 1 ? "The following arguments were not expected: "
                                       : "The following argument was not expected: ") +
                          detail::rjoin(args, " "),
                      ExitCodes::ExtrasError) {}
    ExtrasError(const std::string &name, std::vector<std::string> args)
        : ExtrasError(name,
                      (args.size() > 1 ? "The following arguments were not expected: "
                                       : "The following argument was not expected: ") +
                          detail::rjoin(args, " "),
                      ExitCodes::ExtrasError) {}
};

/// Thrown when extra values are found in an INI file
class ConfigError : public ParseError {
    CLI11_ERROR_DEF(ParseError, ConfigError)
    CLI11_ERROR_SIMPLE(ConfigError)
    static ConfigError Extras(std::string item) { return ConfigError("INI was not able to parse " + item); }
    static ConfigError NotConfigurable(std::string item) {
        return ConfigError(item + ": This option is not allowed in a configuration file");
    }
};

/// Thrown when validation fails before parsing
class InvalidError : public ParseError {
    CLI11_ERROR_DEF(ParseError, InvalidError)
    explicit InvalidError(std::string name)
        : InvalidError(name + ": Too many positional arguments with unlimited expected args", ExitCodes::InvalidError) {
    }
};

/// This is just a safety check to verify selection and parsing match - you should not ever see it
/// Strings are directly added to this error, but again, it should never be seen.
class HorribleError : public ParseError {
    CLI11_ERROR_DEF(ParseError, HorribleError)
    CLI11_ERROR_SIMPLE(HorribleError)
};

// After parsing

/// Thrown when counting a non-existent option
class OptionNotFound : public Error {
    CLI11_ERROR_DEF(Error, OptionNotFound)
    explicit OptionNotFound(std::string name) : OptionNotFound(name + " not found", ExitCodes::OptionNotFound) {}
};

#undef CLI11_ERROR_DEF
#undef CLI11_ERROR_SIMPLE

/// @}


// Type tools

// Utilities for type enabling
namespace detail {
// Based generally on https://rmf.io/cxx11/almost-static-if
/// Simple empty scoped class
enum class enabler {};

/// An instance to use in EnableIf
constexpr enabler dummy = {};
}  // namespace detail

/// A copy of enable_if_t from C++14, compatible with C++11.
///
/// We could check to see if C++14 is being used, but it does not hurt to redefine this
/// (even Google does this: https://github.com/google/skia/blob/master/include/private/SkTLogic.h)
/// It is not in the std namespace anyway, so no harm done.
template <bool B, class T = void> using enable_if_t = typename std::enable_if<B, T>::type;

/// A copy of std::void_t from C++17 (helper for C++11 and C++14)
template <typename... Ts> struct make_void { using type = void; };

/// A copy of std::void_t from C++17 - same reasoning as enable_if_t, it does not hurt to redefine
template <typename... Ts> using void_t = typename make_void<Ts...>::type;

/// A copy of std::conditional_t from C++14 - same reasoning as enable_if_t, it does not hurt to redefine
template <bool B, class T, class F> using conditional_t = typename std::conditional<B, T, F>::type;

/// Check to see if something is bool (fail check by default)
template <typename T> struct is_bool : std::false_type {};

/// Check to see if something is bool (true if actually a bool)
template <> struct is_bool<bool> : std::true_type {};

/// Check to see if something is a shared pointer
template <typename T> struct is_shared_ptr : std::false_type {};

/// Check to see if something is a shared pointer (True if really a shared pointer)
template <typename T> struct is_shared_ptr<std::shared_ptr<T>> : std::true_type {};

/// Check to see if something is a shared pointer (True if really a shared pointer)
template <typename T> struct is_shared_ptr<const std::shared_ptr<T>> : std::true_type {};

/// Check to see if something is copyable pointer
template <typename T> struct is_copyable_ptr {
    static bool const value = is_shared_ptr<T>::value || std::is_pointer<T>::value;
};

/// This can be specialized to override the type deduction for IsMember.
template <typename T> struct IsMemberType { using type = T; };

/// The main custom type needed here is const char * should be a string.
template <> struct IsMemberType<const char *> { using type = std::string; };

namespace detail {

// These are utilities for IsMember and other transforming objects

/// Handy helper to access the element_type generically. This is not part of is_copyable_ptr because it requires that
/// pointer_traits<T> be valid.

/// not a pointer
template <typename T, typename Enable = void> struct element_type { using type = T; };

template <typename T> struct element_type<T, typename std::enable_if<is_copyable_ptr<T>::value>::type> {
    using type = typename std::pointer_traits<T>::element_type;
};

/// Combination of the element type and value type - remove pointer (including smart pointers) and get the value_type of
/// the container
template <typename T> struct element_value_type { using type = typename element_type<T>::type::value_type; };

/// Adaptor for set-like structure: This just wraps a normal container in a few utilities that do almost nothing.
template <typename T, typename _ = void> struct pair_adaptor : std::false_type {
    using value_type = typename T::value_type;
    using first_type = typename std::remove_const<value_type>::type;
    using second_type = typename std::remove_const<value_type>::type;

    /// Get the first value (really just the underlying value)
    template <typename Q> static auto first(Q &&pair_value) -> decltype(std::forward<Q>(pair_value)) {
        return std::forward<Q>(pair_value);
    }
    /// Get the second value (really just the underlying value)
    template <typename Q> static auto second(Q &&pair_value) -> decltype(std::forward<Q>(pair_value)) {
        return std::forward<Q>(pair_value);
    }
};

/// Adaptor for map-like structure (true version, must have key_type and mapped_type).
/// This wraps a mapped container in a few utilities access it in a general way.
template <typename T>
struct pair_adaptor<
    T,
    conditional_t<false, void_t<typename T::value_type::first_type, typename T::value_type::second_type>, void>>
    : std::true_type {
    using value_type = typename T::value_type;
    using first_type = typename std::remove_const<typename value_type::first_type>::type;
    using second_type = typename std::remove_const<typename value_type::second_type>::type;

    /// Get the first value (really just the underlying value)
    template <typename Q> static auto first(Q &&pair_value) -> decltype(std::get<0>(std::forward<Q>(pair_value))) {
        return std::get<0>(std::forward<Q>(pair_value));
    }
    /// Get the second value (really just the underlying value)
    template <typename Q> static auto second(Q &&pair_value) -> decltype(std::get<1>(std::forward<Q>(pair_value))) {
        return std::get<1>(std::forward<Q>(pair_value));
    }
};

// Warning is suppressed due to "bug" in gcc<5.0 and gcc 7.0 with c++17 enabled that generates a Wnarrowing warning
// in the unevaluated context even if the function that was using this wasn't used.  The standard says narrowing in
// brace initialization shouldn't be allowed but for backwards compatibility gcc allows it in some contexts.  It is a
// little fuzzy what happens in template constructs and I think that was something GCC took a little while to work out.
// But regardless some versions of gcc generate a warning when they shouldn't from the following code so that should be
// suppressed
#ifdef __GNUC__
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wnarrowing"
#endif
// check for constructibility from a specific type and copy assignable used in the parse detection
template <typename T, typename C> class is_direct_constructible {
    template <typename TT, typename CC>
    static auto test(int, std::true_type) -> decltype(
// NVCC warns about narrowing conversions here
#ifdef __CUDACC__
#pragma diag_suppress 2361
#endif
        TT { std::declval<CC>() }
#ifdef __CUDACC__
#pragma diag_default 2361
#endif
        ,
        std::is_move_assignable<TT>());

    template <typename TT, typename CC> static auto test(int, std::false_type) -> std::false_type;

    template <typename, typename> static auto test(...) -> std::false_type;

  public:
    static constexpr bool value = decltype(test<T, C>(0, typename std::is_constructible<T, C>::type()))::value;
};
#ifdef __GNUC__
#pragma GCC diagnostic pop
#endif

// Check for output streamability
// Based on https://stackoverflow.com/questions/22758291/how-can-i-detect-if-a-type-can-be-streamed-to-an-stdostream

template <typename T, typename S = std::ostringstream> class is_ostreamable {
    template <typename TT, typename SS>
    static auto test(int) -> decltype(std::declval<SS &>() << std::declval<TT>(), std::true_type());

    template <typename, typename> static auto test(...) -> std::false_type;

  public:
    static constexpr bool value = decltype(test<T, S>(0))::value;
};

/// Check for input streamability
template <typename T, typename S = std::istringstream> class is_istreamable {
    template <typename TT, typename SS>
    static auto test(int) -> decltype(std::declval<SS &>() >> std::declval<TT &>(), std::true_type());

    template <typename, typename> static auto test(...) -> std::false_type;

  public:
    static constexpr bool value = decltype(test<T, S>(0))::value;
};

/// Check for complex
template <typename T> class is_complex {
    template <typename TT>
    static auto test(int) -> decltype(std::declval<TT>().real(), std::declval<TT>().imag(), std::true_type());

    template <typename> static auto test(...) -> std::false_type;

  public:
    static constexpr bool value = decltype(test<T>(0))::value;
};

/// Templated operation to get a value from a stream
template <typename T, enable_if_t<is_istreamable<T>::value, detail::enabler> = detail::dummy>
bool from_stream(const std::string &istring, T &obj) {
    std::istringstream is;
    is.str(istring);
    is >> obj;
    return !is.fail() && !is.rdbuf()->in_avail();
}

template <typename T, enable_if_t<!is_istreamable<T>::value, detail::enabler> = detail::dummy>
bool from_stream(const std::string & /*istring*/, T & /*obj*/) {
    return false;
}

// check to see if an object is a mutable container (fail by default)
template <typename T, typename _ = void> struct is_mutable_container : std::false_type {};

/// type trait to test if a type is a mutable container meaning it has a value_type, it has an iterator, a clear, and
/// end methods and an insert function.  And for our purposes we exclude std::string and types that can be constructed
/// from a std::string
template <typename T>
struct is_mutable_container<
    T,
    conditional_t<false,
                  void_t<typename T::value_type,
                         decltype(std::declval<T>().end()),
                         decltype(std::declval<T>().clear()),
                         decltype(std::declval<T>().insert(std::declval<decltype(std::declval<T>().end())>(),
                                                           std::declval<const typename T::value_type &>()))>,
                  void>>
    : public conditional_t<std::is_constructible<T, std::string>::value, std::false_type, std::true_type> {};

// check to see if an object is a mutable container (fail by default)
template <typename T, typename _ = void> struct is_readable_container : std::false_type {};

/// type trait to test if a type is a container meaning it has a value_type, it has an iterator, a clear, and an end
/// methods and an insert function.  And for our purposes we exclude std::string and types that can be constructed from
/// a std::string
template <typename T>
struct is_readable_container<
    T,
    conditional_t<false, void_t<decltype(std::declval<T>().end()), decltype(std::declval<T>().begin())>, void>>
    : public std::true_type {};

// check to see if an object is a wrapper (fail by default)
template <typename T, typename _ = void> struct is_wrapper : std::false_type {};

// check if an object is a wrapper (it has a value_type defined)
template <typename T>
struct is_wrapper<T, conditional_t<false, void_t<typename T::value_type>, void>> : public std::true_type {};

// Check for tuple like types, as in classes with a tuple_size type trait
template <typename S> class is_tuple_like {
    template <typename SS>
    // static auto test(int)
    //     -> decltype(std::conditional<(std::tuple_size<SS>::value > 0), std::true_type, std::false_type>::type());
    static auto test(int) -> decltype(std::tuple_size<typename std::decay<SS>::type>::value, std::true_type{});
    template <typename> static auto test(...) -> std::false_type;

  public:
    static constexpr bool value = decltype(test<S>(0))::value;
};

/// Convert an object to a string (directly forward if this can become a string)
template <typename T, enable_if_t<std::is_convertible<T, std::string>::value, detail::enabler> = detail::dummy>
auto to_string(T &&value) -> decltype(std::forward<T>(value)) {
    return std::forward<T>(value);
}

/// Construct a string from the object
template <typename T,
          enable_if_t<std::is_constructible<std::string, T>::value && !std::is_convertible<T, std::string>::value,
                      detail::enabler> = detail::dummy>
std::string to_string(const T &value) {
    return std::string(value);
}

/// Convert an object to a string (streaming must be supported for that type)
template <typename T,
          enable_if_t<!std::is_convertible<std::string, T>::value && !std::is_constructible<std::string, T>::value &&
                          is_ostreamable<T>::value,
                      detail::enabler> = detail::dummy>
std::string to_string(T &&value) {
    std::stringstream stream;
    stream << value;
    return stream.str();
}

/// If conversion is not supported, return an empty string (streaming is not supported for that type)
template <typename T,
          enable_if_t<!std::is_constructible<std::string, T>::value && !is_ostreamable<T>::value &&
                          !is_readable_container<typename std::remove_const<T>::type>::value,
                      detail::enabler> = detail::dummy>
std::string to_string(T &&) {
    return std::string{};
}

/// convert a readable container to a string
template <typename T,
          enable_if_t<!std::is_constructible<std::string, T>::value && !is_ostreamable<T>::value &&
                          is_readable_container<T>::value,
                      detail::enabler> = detail::dummy>
std::string to_string(T &&variable) {
    std::vector<std::string> defaults;
    auto cval = variable.begin();
    auto end = variable.end();
    while(cval != end) {
        defaults.emplace_back(CLI::detail::to_string(*cval));
        ++cval;
    }
    return std::string("[" + detail::join(defaults) + "]");
}

/// special template overload
template <typename T1,
          typename T2,
          typename T,
          enable_if_t<std::is_same<T1, T2>::value, detail::enabler> = detail::dummy>
auto checked_to_string(T &&value) -> decltype(to_string(std::forward<T>(value))) {
    return to_string(std::forward<T>(value));
}

/// special template overload
template <typename T1,
          typename T2,
          typename T,
          enable_if_t<!std::is_same<T1, T2>::value, detail::enabler> = detail::dummy>
std::string checked_to_string(T &&) {
    return std::string{};
}
/// get a string as a convertible value for arithmetic types
template <typename T, enable_if_t<std::is_arithmetic<T>::value, detail::enabler> = detail::dummy>
std::string value_string(const T &value) {
    return std::to_string(value);
}
/// get a string as a convertible value for enumerations
template <typename T, enable_if_t<std::is_enum<T>::value, detail::enabler> = detail::dummy>
std::string value_string(const T &value) {
    return std::to_string(static_cast<typename std::underlying_type<T>::type>(value));
}
/// for other types just use the regular to_string function
template <typename T,
          enable_if_t<!std::is_enum<T>::value && !std::is_arithmetic<T>::value, detail::enabler> = detail::dummy>
auto value_string(const T &value) -> decltype(to_string(value)) {
    return to_string(value);
}

/// template to get the underlying value type if it exists or use a default
template <typename T, typename def, typename Enable = void> struct wrapped_type { using type = def; };

/// Type size for regular object types that do not look like a tuple
template <typename T, typename def> struct wrapped_type<T, def, typename std::enable_if<is_wrapper<T>::value>::type> {
    using type = typename T::value_type;
};

/// This will only trigger for actual void type
template <typename T, typename Enable = void> struct type_count_base { static const int value{0}; };

/// Type size for regular object types that do not look like a tuple
template <typename T>
struct type_count_base<T,
                       typename std::enable_if<!is_tuple_like<T>::value && !is_mutable_container<T>::value &&
                                               !std::is_void<T>::value>::type> {
    static constexpr int value{1};
};

/// the base tuple size
template <typename T>
struct type_count_base<T, typename std::enable_if<is_tuple_like<T>::value && !is_mutable_container<T>::value>::type> {
    static constexpr int value{std::tuple_size<T>::value};
};

/// Type count base for containers is the type_count_base of the individual element
template <typename T> struct type_count_base<T, typename std::enable_if<is_mutable_container<T>::value>::type> {
    static constexpr int value{type_count_base<typename T::value_type>::value};
};

/// Set of overloads to get the type size of an object

/// forward declare the subtype_count structure
template <typename T> struct subtype_count;

/// forward declare the subtype_count_min structure
template <typename T> struct subtype_count_min;

/// This will only trigger for actual void type
template <typename T, typename Enable = void> struct type_count { static const int value{0}; };

/// Type size for regular object types that do not look like a tuple
template <typename T>
struct type_count<T,
                  typename std::enable_if<!is_wrapper<T>::value && !is_tuple_like<T>::value && !is_complex<T>::value &&
                                          !std::is_void<T>::value>::type> {
    static constexpr int value{1};
};

/// Type size for complex since it sometimes looks like a wrapper
template <typename T> struct type_count<T, typename std::enable_if<is_complex<T>::value>::type> {
    static constexpr int value{2};
};

/// Type size of types that are wrappers,except complex and tuples(which can also be wrappers sometimes)
template <typename T> struct type_count<T, typename std::enable_if<is_mutable_container<T>::value>::type> {
    static constexpr int value{subtype_count<typename T::value_type>::value};
};

/// Type size of types that are wrappers,except containers complex and tuples(which can also be wrappers sometimes)
template <typename T>
struct type_count<T,
                  typename std::enable_if<is_wrapper<T>::value && !is_complex<T>::value && !is_tuple_like<T>::value &&
                                          !is_mutable_container<T>::value>::type> {
    static constexpr int value{type_count<typename T::value_type>::value};
};

/// 0 if the index > tuple size
template <typename T, std::size_t I>
constexpr typename std::enable_if<I == type_count_base<T>::value, int>::type tuple_type_size() {
    return 0;
}

/// Recursively generate the tuple type name
template <typename T, std::size_t I>
    constexpr typename std::enable_if < I<type_count_base<T>::value, int>::type tuple_type_size() {
    return subtype_count<typename std::tuple_element<I, T>::type>::value + tuple_type_size<T, I + 1>();
}

/// Get the type size of the sum of type sizes for all the individual tuple types
template <typename T> struct type_count<T, typename std::enable_if<is_tuple_like<T>::value>::type> {
    static constexpr int value{tuple_type_size<T, 0>()};
};

/// definition of subtype count
template <typename T> struct subtype_count {
    static constexpr int value{is_mutable_container<T>::value ? expected_max_vector_size : type_count<T>::value};
};

/// This will only trigger for actual void type
template <typename T, typename Enable = void> struct type_count_min { static const int value{0}; };

/// Type size for regular object types that do not look like a tuple
template <typename T>
struct type_count_min<
    T,
    typename std::enable_if<!is_mutable_container<T>::value && !is_tuple_like<T>::value && !is_wrapper<T>::value &&
                            !is_complex<T>::value && !std::is_void<T>::value>::type> {
    static constexpr int value{type_count<T>::value};
};

/// Type size for complex since it sometimes looks like a wrapper
template <typename T> struct type_count_min<T, typename std::enable_if<is_complex<T>::value>::type> {
    static constexpr int value{1};
};

/// Type size min of types that are wrappers,except complex and tuples(which can also be wrappers sometimes)
template <typename T>
struct type_count_min<
    T,
    typename std::enable_if<is_wrapper<T>::value && !is_complex<T>::value && !is_tuple_like<T>::value>::type> {
    static constexpr int value{subtype_count_min<typename T::value_type>::value};
};

/// 0 if the index > tuple size
template <typename T, std::size_t I>
constexpr typename std::enable_if<I == type_count_base<T>::value, int>::type tuple_type_size_min() {
    return 0;
}

/// Recursively generate the tuple type name
template <typename T, std::size_t I>
    constexpr typename std::enable_if < I<type_count_base<T>::value, int>::type tuple_type_size_min() {
    return subtype_count_min<typename std::tuple_element<I, T>::type>::value + tuple_type_size_min<T, I + 1>();
}

/// Get the type size of the sum of type sizes for all the individual tuple types
template <typename T> struct type_count_min<T, typename std::enable_if<is_tuple_like<T>::value>::type> {
    static constexpr int value{tuple_type_size_min<T, 0>()};
};

/// definition of subtype count
template <typename T> struct subtype_count_min {
    static constexpr int value{is_mutable_container<T>::value
                                   ? ((type_count<T>::value < expected_max_vector_size) ? type_count<T>::value : 0)
                                   : type_count_min<T>::value};
};

/// This will only trigger for actual void type
template <typename T, typename Enable = void> struct expected_count { static const int value{0}; };

/// For most types the number of expected items is 1
template <typename T>
struct expected_count<T,
                      typename std::enable_if<!is_mutable_container<T>::value && !is_wrapper<T>::value &&
                                              !std::is_void<T>::value>::type> {
    static constexpr int value{1};
};
/// number of expected items in a vector
template <typename T> struct expected_count<T, typename std::enable_if<is_mutable_container<T>::value>::type> {
    static constexpr int value{expected_max_vector_size};
};

/// number of expected items in a vector
template <typename T>
struct expected_count<T, typename std::enable_if<!is_mutable_container<T>::value && is_wrapper<T>::value>::type> {
    static constexpr int value{expected_count<typename T::value_type>::value};
};

// Enumeration of the different supported categorizations of objects
enum class object_category : int {
    char_value = 1,
    integral_value = 2,
    unsigned_integral = 4,
    enumeration = 6,
    boolean_value = 8,
    floating_point = 10,
    number_constructible = 12,
    double_constructible = 14,
    integer_constructible = 16,
    // string like types
    string_assignable = 23,
    string_constructible = 24,
    other = 45,
    // special wrapper or container types
    wrapper_value = 50,
    complex_number = 60,
    tuple_value = 70,
    container_value = 80,

};

/// Set of overloads to classify an object according to type

/// some type that is not otherwise recognized
template <typename T, typename Enable = void> struct classify_object {
    static constexpr object_category value{object_category::other};
};

/// Signed integers
template <typename T>
struct classify_object<
    T,
    typename std::enable_if<std::is_integral<T>::value && !std::is_same<T, char>::value && std::is_signed<T>::value &&
                            !is_bool<T>::value && !std::is_enum<T>::value>::type> {
    static constexpr object_category value{object_category::integral_value};
};

/// Unsigned integers
template <typename T>
struct classify_object<T,
                       typename std::enable_if<std::is_integral<T>::value && std::is_unsigned<T>::value &&
                                               !std::is_same<T, char>::value && !is_bool<T>::value>::type> {
    static constexpr object_category value{object_category::unsigned_integral};
};

/// single character values
template <typename T>
struct classify_object<T, typename std::enable_if<std::is_same<T, char>::value && !std::is_enum<T>::value>::type> {
    static constexpr object_category value{object_category::char_value};
};

/// Boolean values
template <typename T> struct classify_object<T, typename std::enable_if<is_bool<T>::value>::type> {
    static constexpr object_category value{object_category::boolean_value};
};

/// Floats
template <typename T> struct classify_object<T, typename std::enable_if<std::is_floating_point<T>::value>::type> {
    static constexpr object_category value{object_category::floating_point};
};

/// String and similar direct assignment
template <typename T>
struct classify_object<T,
                       typename std::enable_if<!std::is_floating_point<T>::value && !std::is_integral<T>::value &&
                                               std::is_assignable<T &, std::string>::value>::type> {
    static constexpr object_category value{object_category::string_assignable};
};

/// String and similar constructible and copy assignment
template <typename T>
struct classify_object<
    T,
    typename std::enable_if<!std::is_floating_point<T>::value && !std::is_integral<T>::value &&
                            !std::is_assignable<T &, std::string>::value && (type_count<T>::value == 1) &&
                            std::is_constructible<T, std::string>::value>::type> {
    static constexpr object_category value{object_category::string_constructible};
};

/// Enumerations
template <typename T> struct classify_object<T, typename std::enable_if<std::is_enum<T>::value>::type> {
    static constexpr object_category value{object_category::enumeration};
};

template <typename T> struct classify_object<T, typename std::enable_if<is_complex<T>::value>::type> {
    static constexpr object_category value{object_category::complex_number};
};

/// Handy helper to contain a bunch of checks that rule out many common types (integers, string like, floating point,
/// vectors, and enumerations
template <typename T> struct uncommon_type {
    using type = typename std::conditional<!std::is_floating_point<T>::value && !std::is_integral<T>::value &&
                                               !std::is_assignable<T &, std::string>::value &&
                                               !std::is_constructible<T, std::string>::value && !is_complex<T>::value &&
                                               !is_mutable_container<T>::value && !std::is_enum<T>::value,
                                           std::true_type,
                                           std::false_type>::type;
    static constexpr bool value = type::value;
};

/// wrapper type
template <typename T>
struct classify_object<T,
                       typename std::enable_if<(!is_mutable_container<T>::value && is_wrapper<T>::value &&
                                                !is_tuple_like<T>::value && uncommon_type<T>::value)>::type> {
    static constexpr object_category value{object_category::wrapper_value};
};

/// Assignable from double or int
template <typename T>
struct classify_object<T,
                       typename std::enable_if<uncommon_type<T>::value && type_count<T>::value == 1 &&
                                               !is_wrapper<T>::value && is_direct_constructible<T, double>::value &&
                                               is_direct_constructible<T, int>::value>::type> {
    static constexpr object_category value{object_category::number_constructible};
};

/// Assignable from int
template <typename T>
struct classify_object<T,
                       typename std::enable_if<uncommon_type<T>::value && type_count<T>::value == 1 &&
                                               !is_wrapper<T>::value && !is_direct_constructible<T, double>::value &&
                                               is_direct_constructible<T, int>::value>::type> {
    static constexpr object_category value{object_category::integer_constructible};
};

/// Assignable from double
template <typename T>
struct classify_object<T,
                       typename std::enable_if<uncommon_type<T>::value && type_count<T>::value == 1 &&
                                               !is_wrapper<T>::value && is_direct_constructible<T, double>::value &&
                                               !is_direct_constructible<T, int>::value>::type> {
    static constexpr object_category value{object_category::double_constructible};
};

/// Tuple type
template <typename T>
struct classify_object<
    T,
    typename std::enable_if<is_tuple_like<T>::value &&
                            ((type_count<T>::value >= 2 && !is_wrapper<T>::value) ||
                             (uncommon_type<T>::value && !is_direct_constructible<T, double>::value &&
                              !is_direct_constructible<T, int>::value))>::type> {
    static constexpr object_category value{object_category::tuple_value};
    // the condition on this class requires it be like a tuple, but on some compilers (like Xcode) tuples can be
    // constructed from just the first element so tuples of <string, int,int> can be constructed from a string, which
    // could lead to issues so there are two variants of the condition, the first isolates things with a type size >=2
    // mainly to get tuples on Xcode with the exception of wrappers, the second is the main one and just separating out
    // those cases that are caught by other object classifications
};

/// container type
template <typename T> struct classify_object<T, typename std::enable_if<is_mutable_container<T>::value>::type> {
    static constexpr object_category value{object_category::container_value};
};

// Type name print

/// Was going to be based on
///  http://stackoverflow.com/questions/1055452/c-get-name-of-type-in-template
/// But this is cleaner and works better in this case

template <typename T,
          enable_if_t<classify_object<T>::value == object_category::char_value, detail::enabler> = detail::dummy>
constexpr const char *type_name() {
    return "CHAR";
}

template <typename T,
          enable_if_t<classify_object<T>::value == object_category::integral_value ||
                          classify_object<T>::value == object_category::integer_constructible,
                      detail::enabler> = detail::dummy>
constexpr const char *type_name() {
    return "INT";
}

template <typename T,
          enable_if_t<classify_object<T>::value == object_category::unsigned_integral, detail::enabler> = detail::dummy>
constexpr const char *type_name() {
    return "UINT";
}

template <typename T,
          enable_if_t<classify_object<T>::value == object_category::floating_point ||
                          classify_object<T>::value == object_category::number_constructible ||
                          classify_object<T>::value == object_category::double_constructible,
                      detail::enabler> = detail::dummy>
constexpr const char *type_name() {
    return "FLOAT";
}

/// Print name for enumeration types
template <typename T,
          enable_if_t<classify_object<T>::value == object_category::enumeration, detail::enabler> = detail::dummy>
constexpr const char *type_name() {
    return "ENUM";
}

/// Print name for enumeration types
template <typename T,
          enable_if_t<classify_object<T>::value == object_category::boolean_value, detail::enabler> = detail::dummy>
constexpr const char *type_name() {
    return "BOOLEAN";
}

/// Print name for enumeration types
template <typename T,
          enable_if_t<classify_object<T>::value == object_category::complex_number, detail::enabler> = detail::dummy>
constexpr const char *type_name() {
    return "COMPLEX";
}

/// Print for all other types
template <typename T,
          enable_if_t<classify_object<T>::value >= object_category::string_assignable &&
                          classify_object<T>::value <= object_category::other,
                      detail::enabler> = detail::dummy>
constexpr const char *type_name() {
    return "TEXT";
}
/// typename for tuple value
template <typename T,
          enable_if_t<classify_object<T>::value == object_category::tuple_value && type_count_base<T>::value >= 2,
                      detail::enabler> = detail::dummy>
std::string type_name();  // forward declaration

/// Generate type name for a wrapper or container value
template <typename T,
          enable_if_t<classify_object<T>::value == object_category::container_value ||
                          classify_object<T>::value == object_category::wrapper_value,
                      detail::enabler> = detail::dummy>
std::string type_name();  // forward declaration

/// Print name for single element tuple types
template <typename T,
          enable_if_t<classify_object<T>::value == object_category::tuple_value && type_count_base<T>::value == 1,
                      detail::enabler> = detail::dummy>
inline std::string type_name() {
    return type_name<typename std::decay<typename std::tuple_element<0, T>::type>::type>();
}

/// Empty string if the index > tuple size
template <typename T, std::size_t I>
inline typename std::enable_if<I == type_count_base<T>::value, std::string>::type tuple_name() {
    return std::string{};
}

/// Recursively generate the tuple type name
template <typename T, std::size_t I>
inline typename std::enable_if<(I < type_count_base<T>::value), std::string>::type tuple_name() {
    std::string str = std::string(type_name<typename std::decay<typename std::tuple_element<I, T>::type>::type>()) +
                      ',' + tuple_name<T, I + 1>();
    if(str.back() == ',')
        str.pop_back();
    return str;
}

/// Print type name for tuples with 2 or more elements
template <typename T,
          enable_if_t<classify_object<T>::value == object_category::tuple_value && type_count_base<T>::value >= 2,
                      detail::enabler>>
inline std::string type_name() {
    auto tname = std::string(1, '[') + tuple_name<T, 0>();
    tname.push_back(']');
    return tname;
}

/// get the type name for a type that has a value_type member
template <typename T,
          enable_if_t<classify_object<T>::value == object_category::container_value ||
                          classify_object<T>::value == object_category::wrapper_value,
                      detail::enabler>>
inline std::string type_name() {
    return type_name<typename T::value_type>();
}

// Lexical cast

/// Convert to an unsigned integral
template <typename T, enable_if_t<std::is_unsigned<T>::value, detail::enabler> = detail::dummy>
bool integral_conversion(const std::string &input, T &output) noexcept {
    if(input.empty()) {
        return false;
    }
    char *val = nullptr;
    std::uint64_t output_ll = std::strtoull(input.c_str(), &val, 0);
    output = static_cast<T>(output_ll);
    return val == (input.c_str() + input.size()) && static_cast<std::uint64_t>(output) == output_ll;
}

/// Convert to a signed integral
template <typename T, enable_if_t<std::is_signed<T>::value, detail::enabler> = detail::dummy>
bool integral_conversion(const std::string &input, T &output) noexcept {
    if(input.empty()) {
        return false;
    }
    char *val = nullptr;
    std::int64_t output_ll = std::strtoll(input.c_str(), &val, 0);
    output = static_cast<T>(output_ll);
    return val == (input.c_str() + input.size()) && static_cast<std::int64_t>(output) == output_ll;
}

/// Convert a flag into an integer value  typically binary flags
inline std::int64_t to_flag_value(std::string val) {
    static const std::string trueString("true");
    static const std::string falseString("false");
    if(val == trueString) {
        return 1;
    }
    if(val == falseString) {
        return -1;
    }
    val = detail::to_lower(val);
    std::int64_t ret;
    if(val.size() == 1) {
        if(val[0] >= '1' && val[0] <= '9') {
            return (static_cast<std::int64_t>(val[0]) - '0');
        }
        switch(val[0]) {
        case '0':
        case 'f':
        case 'n':
        case '-':
            ret = -1;
            break;
        case 't':
        case 'y':
        case '+':
            ret = 1;
            break;
        default:
            throw std::invalid_argument("unrecognized character");
        }
        return ret;
    }
    if(val == trueString || val == "on" || val == "yes" || val == "enable") {
        ret = 1;
    } else if(val == falseString || val == "off" || val == "no" || val == "disable") {
        ret = -1;
    } else {
        ret = std::stoll(val);
    }
    return ret;
}

/// Integer conversion
template <typename T,
          enable_if_t<classify_object<T>::value == object_category::integral_value ||
                          classify_object<T>::value == object_category::unsigned_integral,
                      detail::enabler> = detail::dummy>
bool lexical_cast(const std::string &input, T &output) {
    return integral_conversion(input, output);
}

/// char values
template <typename T,
          enable_if_t<classify_object<T>::value == object_category::char_value, detail::enabler> = detail::dummy>
bool lexical_cast(const std::string &input, T &output) {
    if(input.size() == 1) {
        output = static_cast<T>(input[0]);
        return true;
    }
    return integral_conversion(input, output);
}

/// Boolean values
template <typename T,
          enable_if_t<classify_object<T>::value == object_category::boolean_value, detail::enabler> = detail::dummy>
bool lexical_cast(const std::string &input, T &output) {
    try {
        auto out = to_flag_value(input);
        output = (out > 0);
        return true;
    } catch(const std::invalid_argument &) {
        return false;
    } catch(const std::out_of_range &) {
        // if the number is out of the range of a 64 bit value then it is still a number and for this purpose is still
        // valid all we care about the sign
        output = (input[0] != '-');
        return true;
    }
}

/// Floats
template <typename T,
          enable_if_t<classify_object<T>::value == object_category::floating_point, detail::enabler> = detail::dummy>
bool lexical_cast(const std::string &input, T &output) {
    if(input.empty()) {
        return false;
    }
    char *val = nullptr;
    auto output_ld = std::strtold(input.c_str(), &val);
    output = static_cast<T>(output_ld);
    return val == (input.c_str() + input.size());
}

/// complex
template <typename T,
          enable_if_t<classify_object<T>::value == object_category::complex_number, detail::enabler> = detail::dummy>
bool lexical_cast(const std::string &input, T &output) {
    using XC = typename wrapped_type<T, double>::type;
    XC x{0.0}, y{0.0};
    auto str1 = input;
    bool worked = false;
    auto nloc = str1.find_last_of("+-");
    if(nloc != std::string::npos && nloc > 0) {
        worked = detail::lexical_cast(str1.substr(0, nloc), x);
        str1 = str1.substr(nloc);
        if(str1.back() == 'i' || str1.back() == 'j')
            str1.pop_back();
        worked = worked && detail::lexical_cast(str1, y);
    } else {
        if(str1.back() == 'i' || str1.back() == 'j') {
            str1.pop_back();
            worked = detail::lexical_cast(str1, y);
            x = XC{0};
        } else {
            worked = detail::lexical_cast(str1, x);
            y = XC{0};
        }
    }
    if(worked) {
        output = T{x, y};
        return worked;
    }
    return from_stream(input, output);
}

/// String and similar direct assignment
template <typename T,
          enable_if_t<classify_object<T>::value == object_category::string_assignable, detail::enabler> = detail::dummy>
bool lexical_cast(const std::string &input, T &output) {
    output = input;
    return true;
}

/// String and similar constructible and copy assignment
template <
    typename T,
    enable_if_t<classify_object<T>::value == object_category::string_constructible, detail::enabler> = detail::dummy>
bool lexical_cast(const std::string &input, T &output) {
    output = T(input);
    return true;
}

/// Enumerations
template <typename T,
          enable_if_t<classify_object<T>::value == object_category::enumeration, detail::enabler> = detail::dummy>
bool lexical_cast(const std::string &input, T &output) {
    typename std::underlying_type<T>::type val;
    if(!integral_conversion(input, val)) {
        return false;
    }
    output = static_cast<T>(val);
    return true;
}

/// wrapper types
template <typename T,
          enable_if_t<classify_object<T>::value == object_category::wrapper_value &&
                          std::is_assignable<T &, typename T::value_type>::value,
                      detail::enabler> = detail::dummy>
bool lexical_cast(const std::string &input, T &output) {
    typename T::value_type val;
    if(lexical_cast(input, val)) {
        output = val;
        return true;
    }
    return from_stream(input, output);
}

template <typename T,
          enable_if_t<classify_object<T>::value == object_category::wrapper_value &&
                          !std::is_assignable<T &, typename T::value_type>::value && std::is_assignable<T &, T>::value,
                      detail::enabler> = detail::dummy>
bool lexical_cast(const std::string &input, T &output) {
    typename T::value_type val;
    if(lexical_cast(input, val)) {
        output = T{val};
        return true;
    }
    return from_stream(input, output);
}

/// Assignable from double or int
template <
    typename T,
    enable_if_t<classify_object<T>::value == object_category::number_constructible, detail::enabler> = detail::dummy>
bool lexical_cast(const std::string &input, T &output) {
    int val;
    if(integral_conversion(input, val)) {
        output = T(val);
        return true;
    } else {
        double dval;
        if(lexical_cast(input, dval)) {
            output = T{dval};
            return true;
        }
    }
    return from_stream(input, output);
}

/// Assignable from int
template <
    typename T,
    enable_if_t<classify_object<T>::value == object_category::integer_constructible, detail::enabler> = detail::dummy>
bool lexical_cast(const std::string &input, T &output) {
    int val;
    if(integral_conversion(input, val)) {
        output = T(val);
        return true;
    }
    return from_stream(input, output);
}

/// Assignable from double
template <
    typename T,
    enable_if_t<classify_object<T>::value == object_category::double_constructible, detail::enabler> = detail::dummy>
bool lexical_cast(const std::string &input, T &output) {
    double val;
    if(lexical_cast(input, val)) {
        output = T{val};
        return true;
    }
    return from_stream(input, output);
}

/// Non-string convertible from an int
template <typename T,
          enable_if_t<classify_object<T>::value == object_category::other && std::is_assignable<T &, int>::value,
                      detail::enabler> = detail::dummy>
bool lexical_cast(const std::string &input, T &output) {
    int val;
    if(integral_conversion(input, val)) {
#ifdef _MSC_VER
#pragma warning(push)
#pragma warning(disable : 4800)
#endif
        // with Atomic<XX> this could produce a warning due to the conversion but if atomic gets here it is an old style
        // so will most likely still work
        output = val;
#ifdef _MSC_VER
#pragma warning(pop)
#endif
        return true;
    }
    // LCOV_EXCL_START
    // This version of cast is only used for odd cases in an older compilers the fail over
    // from_stream is tested elsewhere an not relevant for coverage here
    return from_stream(input, output);
    // LCOV_EXCL_STOP
}

/// Non-string parsable by a stream
template <typename T,
          enable_if_t<classify_object<T>::value == object_category::other && !std::is_assignable<T &, int>::value,
                      detail::enabler> = detail::dummy>
bool lexical_cast(const std::string &input, T &output) {
    static_assert(is_istreamable<T>::value,
                  "option object type must have a lexical cast overload or streaming input operator(>>) defined, if it "
                  "is convertible from another type use the add_option<T, XC>(...) with XC being the known type");
    return from_stream(input, output);
}

/// Assign a value through lexical cast operations
/// Strings can be empty so we need to do a little different
template <typename AssignTo,
          typename ConvertTo,
          enable_if_t<std::is_same<AssignTo, ConvertTo>::value &&
                          (classify_object<AssignTo>::value == object_category::string_assignable ||
                           classify_object<AssignTo>::value == object_category::string_constructible),
                      detail::enabler> = detail::dummy>
bool lexical_assign(const std::string &input, AssignTo &output) {
    return lexical_cast(input, output);
}

/// Assign a value through lexical cast operations
template <typename AssignTo,
          typename ConvertTo,
          enable_if_t<std::is_same<AssignTo, ConvertTo>::value && std::is_assignable<AssignTo &, AssignTo>::value &&
                          classify_object<AssignTo>::value != object_category::string_assignable &&
                          classify_object<AssignTo>::value != object_category::string_constructible,
                      detail::enabler> = detail::dummy>
bool lexical_assign(const std::string &input, AssignTo &output) {
    if(input.empty()) {
        output = AssignTo{};
        return true;
    }

    return lexical_cast(input, output);
}

/// Assign a value through lexical cast operations
template <typename AssignTo,
          typename ConvertTo,
          enable_if_t<std::is_same<AssignTo, ConvertTo>::value && !std::is_assignable<AssignTo &, AssignTo>::value &&
                          classify_object<AssignTo>::value == object_category::wrapper_value,
                      detail::enabler> = detail::dummy>
bool lexical_assign(const std::string &input, AssignTo &output) {
    if(input.empty()) {
        typename AssignTo::value_type emptyVal{};
        output = emptyVal;
        return true;
    }
    return lexical_cast(input, output);
}

/// Assign a value through lexical cast operations for int compatible values
/// mainly for atomic operations on some compilers
template <typename AssignTo,
          typename ConvertTo,
          enable_if_t<std::is_same<AssignTo, ConvertTo>::value && !std::is_assignable<AssignTo &, AssignTo>::value &&
                          classify_object<AssignTo>::value != object_category::wrapper_value &&
                          std::is_assignable<AssignTo &, int>::value,
                      detail::enabler> = detail::dummy>
bool lexical_assign(const std::string &input, AssignTo &output) {
    if(input.empty()) {
        output = 0;
        return true;
    }
    int val;
    if(lexical_cast(input, val)) {
        output = val;
        return true;
    }
    return false;
}

/// Assign a value converted from a string in lexical cast to the output value directly
template <typename AssignTo,
          typename ConvertTo,
          enable_if_t<!std::is_same<AssignTo, ConvertTo>::value && std::is_assignable<AssignTo &, ConvertTo &>::value,
                      detail::enabler> = detail::dummy>
bool lexical_assign(const std::string &input, AssignTo &output) {
    ConvertTo val{};
    bool parse_result = (!input.empty()) ? lexical_cast<ConvertTo>(input, val) : true;
    if(parse_result) {
        output = val;
    }
    return parse_result;
}

/// Assign a value from a lexical cast through constructing a value and move assigning it
template <
    typename AssignTo,
    typename ConvertTo,
    enable_if_t<!std::is_same<AssignTo, ConvertTo>::value && !std::is_assignable<AssignTo &, ConvertTo &>::value &&
                    std::is_move_assignable<AssignTo>::value,
                detail::enabler> = detail::dummy>
bool lexical_assign(const std::string &input, AssignTo &output) {
    ConvertTo val{};
    bool parse_result = input.empty() ? true : lexical_cast<ConvertTo>(input, val);
    if(parse_result) {
        output = AssignTo(val);  // use () form of constructor to allow some implicit conversions
    }
    return parse_result;
}

/// primary lexical conversion operation, 1 string to 1 type of some kind
template <typename AssignTo,
          typename ConvertTo,
          enable_if_t<classify_object<ConvertTo>::value <= object_category::other &&
                          classify_object<AssignTo>::value <= object_category::wrapper_value,
                      detail::enabler> = detail::dummy>
bool lexical_conversion(const std::vector<std ::string> &strings, AssignTo &output) {
    return lexical_assign<AssignTo, ConvertTo>(strings[0], output);
}

/// Lexical conversion if there is only one element but the conversion type is for two, then call a two element
/// constructor
template <typename AssignTo,
          typename ConvertTo,
          enable_if_t<(type_count<AssignTo>::value <= 2) && expected_count<AssignTo>::value == 1 &&
                          is_tuple_like<ConvertTo>::value && type_count_base<ConvertTo>::value == 2,
                      detail::enabler> = detail::dummy>
bool lexical_conversion(const std::vector<std ::string> &strings, AssignTo &output) {
    // the remove const is to handle pair types coming from a container
    typename std::remove_const<typename std::tuple_element<0, ConvertTo>::type>::type v1;
    typename std::tuple_element<1, ConvertTo>::type v2;
    bool retval = lexical_assign<decltype(v1), decltype(v1)>(strings[0], v1);
    if(strings.size() > 1) {
        retval = retval && lexical_assign<decltype(v2), decltype(v2)>(strings[1], v2);
    }
    if(retval) {
        output = AssignTo{v1, v2};
    }
    return retval;
}

/// Lexical conversion of a container types of single elements
template <class AssignTo,
          class ConvertTo,
          enable_if_t<is_mutable_container<AssignTo>::value && is_mutable_container<ConvertTo>::value &&
                          type_count<ConvertTo>::value == 1,
                      detail::enabler> = detail::dummy>
bool lexical_conversion(const std::vector<std ::string> &strings, AssignTo &output) {
    output.erase(output.begin(), output.end());
    for(const auto &elem : strings) {
        typename AssignTo::value_type out;
        bool retval = lexical_assign<typename AssignTo::value_type, typename ConvertTo::value_type>(elem, out);
        if(!retval) {
            return false;
        }
        output.insert(output.end(), std::move(out));
    }
    return (!output.empty());
}

/// Lexical conversion for complex types
template <class AssignTo, class ConvertTo, enable_if_t<is_complex<ConvertTo>::value, detail::enabler> = detail::dummy>
bool lexical_conversion(const std::vector<std::string> &strings, AssignTo &output) {

    if(strings.size() >= 2 && !strings[1].empty()) {
        using XC2 = typename wrapped_type<ConvertTo, double>::type;
        XC2 x{0.0}, y{0.0};
        auto str1 = strings[1];
        if(str1.back() == 'i' || str1.back() == 'j') {
            str1.pop_back();
        }
        auto worked = detail::lexical_cast(strings[0], x) && detail::lexical_cast(str1, y);
        if(worked) {
            output = ConvertTo{x, y};
        }
        return worked;
    } else {
        return lexical_assign<AssignTo, ConvertTo>(strings[0], output);
    }
}

/// Conversion to a vector type using a particular single type as the conversion type
template <class AssignTo,
          class ConvertTo,
          enable_if_t<is_mutable_container<AssignTo>::value && (expected_count<ConvertTo>::value == 1) &&
                          (type_count<ConvertTo>::value == 1),
                      detail::enabler> = detail::dummy>
bool lexical_conversion(const std::vector<std ::string> &strings, AssignTo &output) {
    bool retval = true;
    output.clear();
    output.reserve(strings.size());
    for(const auto &elem : strings) {

        output.emplace_back();
        retval = retval && lexical_assign<typename AssignTo::value_type, ConvertTo>(elem, output.back());
    }
    return (!output.empty()) && retval;
}

// forward declaration

/// Lexical conversion of a container types with conversion type of two elements
template <class AssignTo,
          class ConvertTo,
          enable_if_t<is_mutable_container<AssignTo>::value && is_mutable_container<ConvertTo>::value &&
                          type_count_base<ConvertTo>::value == 2,
                      detail::enabler> = detail::dummy>
bool lexical_conversion(std::vector<std::string> strings, AssignTo &output);

/// Lexical conversion of a vector types with type_size >2 forward declaration
template <class AssignTo,
          class ConvertTo,
          enable_if_t<is_mutable_container<AssignTo>::value && is_mutable_container<ConvertTo>::value &&
                          type_count_base<ConvertTo>::value != 2 &&
                          ((type_count<ConvertTo>::value > 2) ||
                           (type_count<ConvertTo>::value > type_count_base<ConvertTo>::value)),
                      detail::enabler> = detail::dummy>
bool lexical_conversion(const std::vector<std::string> &strings, AssignTo &output);

/// Conversion for tuples
template <class AssignTo,
          class ConvertTo,
          enable_if_t<is_tuple_like<AssignTo>::value && is_tuple_like<ConvertTo>::value &&
                          (type_count_base<ConvertTo>::value != type_count<ConvertTo>::value ||
                           type_count<ConvertTo>::value > 2),
                      detail::enabler> = detail::dummy>
bool lexical_conversion(const std::vector<std::string> &strings, AssignTo &output);  // forward declaration

/// Conversion for operations where the assigned type is some class but the conversion is a mutable container or large
/// tuple
template <typename AssignTo,
          typename ConvertTo,
          enable_if_t<!is_tuple_like<AssignTo>::value && !is_mutable_container<AssignTo>::value &&
                          classify_object<ConvertTo>::value != object_category::wrapper_value &&
                          (is_mutable_container<ConvertTo>::value || type_count<ConvertTo>::value > 2),
                      detail::enabler> = detail::dummy>
bool lexical_conversion(const std::vector<std ::string> &strings, AssignTo &output) {

    if(strings.size() > 1 || (!strings.empty() && !(strings.front().empty()))) {
        ConvertTo val;
        auto retval = lexical_conversion<ConvertTo, ConvertTo>(strings, val);
        output = AssignTo{val};
        return retval;
    }
    output = AssignTo{};
    return true;
}

/// function template for converting tuples if the static Index is greater than the tuple size
template <class AssignTo, class ConvertTo, std::size_t I>
inline typename std::enable_if<(I >= type_count_base<AssignTo>::value), bool>::type
tuple_conversion(const std::vector<std::string> &, AssignTo &) {
    return true;
}

/// Conversion of a tuple element where the type size ==1 and not a mutable container
template <class AssignTo, class ConvertTo>
inline typename std::enable_if<!is_mutable_container<ConvertTo>::value && type_count<ConvertTo>::value == 1, bool>::type
tuple_type_conversion(std::vector<std::string> &strings, AssignTo &output) {
    auto retval = lexical_assign<AssignTo, ConvertTo>(strings[0], output);
    strings.erase(strings.begin());
    return retval;
}

/// Conversion of a tuple element where the type size !=1 but the size is fixed and not a mutable container
template <class AssignTo, class ConvertTo>
inline typename std::enable_if<!is_mutable_container<ConvertTo>::value && (type_count<ConvertTo>::value > 1) &&
                                   type_count<ConvertTo>::value == type_count_min<ConvertTo>::value,
                               bool>::type
tuple_type_conversion(std::vector<std::string> &strings, AssignTo &output) {
    auto retval = lexical_conversion<AssignTo, ConvertTo>(strings, output);
    strings.erase(strings.begin(), strings.begin() + type_count<ConvertTo>::value);
    return retval;
}

/// Conversion of a tuple element where the type is a mutable container or a type with different min and max type sizes
template <class AssignTo, class ConvertTo>
inline typename std::enable_if<is_mutable_container<ConvertTo>::value ||
                                   type_count<ConvertTo>::value != type_count_min<ConvertTo>::value,
                               bool>::type
tuple_type_conversion(std::vector<std::string> &strings, AssignTo &output) {

    std::size_t index{subtype_count_min<ConvertTo>::value};
    const std::size_t mx_count{subtype_count<ConvertTo>::value};
    const std::size_t mx{(std::max)(mx_count, strings.size())};

    while(index < mx) {
        if(is_separator(strings[index])) {
            break;
        }
        ++index;
    }
    bool retval = lexical_conversion<AssignTo, ConvertTo>(
        std::vector<std::string>(strings.begin(), strings.begin() + static_cast<std::ptrdiff_t>(index)), output);
    strings.erase(strings.begin(), strings.begin() + static_cast<std::ptrdiff_t>(index) + 1);
    return retval;
}

/// Tuple conversion operation
template <class AssignTo, class ConvertTo, std::size_t I>
inline typename std::enable_if<(I < type_count_base<AssignTo>::value), bool>::type
tuple_conversion(std::vector<std::string> strings, AssignTo &output) {
    bool retval = true;
    using ConvertToElement = typename std::
        conditional<is_tuple_like<ConvertTo>::value, typename std::tuple_element<I, ConvertTo>::type, ConvertTo>::type;
    if(!strings.empty()) {
        retval = retval && tuple_type_conversion<typename std::tuple_element<I, AssignTo>::type, ConvertToElement>(
                               strings, std::get<I>(output));
    }
    retval = retval && tuple_conversion<AssignTo, ConvertTo, I + 1>(std::move(strings), output);
    return retval;
}

/// Lexical conversion of a container types with tuple elements of size 2
template <class AssignTo,
          class ConvertTo,
          enable_if_t<is_mutable_container<AssignTo>::value && is_mutable_container<ConvertTo>::value &&
                          type_count_base<ConvertTo>::value == 2,
                      detail::enabler>>
bool lexical_conversion(std::vector<std::string> strings, AssignTo &output) {
    output.clear();
    while(!strings.empty()) {

        typename std::remove_const<typename std::tuple_element<0, typename ConvertTo::value_type>::type>::type v1;
        typename std::tuple_element<1, typename ConvertTo::value_type>::type v2;
        bool retval = tuple_type_conversion<decltype(v1), decltype(v1)>(strings, v1);
        if(!strings.empty()) {
            retval = retval && tuple_type_conversion<decltype(v2), decltype(v2)>(strings, v2);
        }
        if(retval) {
            output.insert(output.end(), typename AssignTo::value_type{v1, v2});
        } else {
            return false;
        }
    }
    return (!output.empty());
}

/// lexical conversion of tuples with type count>2 or tuples of types of some element with a type size>=2
template <class AssignTo,
          class ConvertTo,
          enable_if_t<is_tuple_like<AssignTo>::value && is_tuple_like<ConvertTo>::value &&
                          (type_count_base<ConvertTo>::value != type_count<ConvertTo>::value ||
                           type_count<ConvertTo>::value > 2),
                      detail::enabler>>
bool lexical_conversion(const std::vector<std ::string> &strings, AssignTo &output) {
    static_assert(
        !is_tuple_like<ConvertTo>::value || type_count_base<AssignTo>::value == type_count_base<ConvertTo>::value,
        "if the conversion type is defined as a tuple it must be the same size as the type you are converting to");
    return tuple_conversion<AssignTo, ConvertTo, 0>(strings, output);
}

/// Lexical conversion of a vector types for everything but tuples of two elements and types of size 1
template <class AssignTo,
          class ConvertTo,
          enable_if_t<is_mutable_container<AssignTo>::value && is_mutable_container<ConvertTo>::value &&
                          type_count_base<ConvertTo>::value != 2 &&
                          ((type_count<ConvertTo>::value > 2) ||
                           (type_count<ConvertTo>::value > type_count_base<ConvertTo>::value)),
                      detail::enabler>>
bool lexical_conversion(const std::vector<std ::string> &strings, AssignTo &output) {
    bool retval = true;
    output.clear();
    std::vector<std::string> temp;
    std::size_t ii{0};
    std::size_t icount{0};
    std::size_t xcm{type_count<ConvertTo>::value};
    auto ii_max = strings.size();
    while(ii < ii_max) {
        temp.push_back(strings[ii]);
        ++ii;
        ++icount;
        if(icount == xcm || is_separator(temp.back()) || ii == ii_max) {
            if(static_cast<int>(xcm) > type_count_min<ConvertTo>::value && is_separator(temp.back())) {
                temp.pop_back();
            }
            typename AssignTo::value_type temp_out;
            retval = retval &&
                     lexical_conversion<typename AssignTo::value_type, typename ConvertTo::value_type>(temp, temp_out);
            temp.clear();
            if(!retval) {
                return false;
            }
            output.insert(output.end(), std::move(temp_out));
            icount = 0;
        }
    }
    return retval;
}

/// conversion for wrapper types
template <typename AssignTo,
          class ConvertTo,
          enable_if_t<classify_object<ConvertTo>::value == object_category::wrapper_value &&
                          std::is_assignable<ConvertTo &, ConvertTo>::value,
                      detail::enabler> = detail::dummy>
bool lexical_conversion(const std::vector<std::string> &strings, AssignTo &output) {
    if(strings.empty() || strings.front().empty()) {
        output = ConvertTo{};
        return true;
    }
    typename ConvertTo::value_type val;
    if(lexical_conversion<typename ConvertTo::value_type, typename ConvertTo::value_type>(strings, val)) {
        output = ConvertTo{val};
        return true;
    }
    return false;
}

/// conversion for wrapper types
template <typename AssignTo,
          class ConvertTo,
          enable_if_t<classify_object<ConvertTo>::value == object_category::wrapper_value &&
                          !std::is_assignable<AssignTo &, ConvertTo>::value,
                      detail::enabler> = detail::dummy>
bool lexical_conversion(const std::vector<std::string> &strings, AssignTo &output) {
    using ConvertType = typename ConvertTo::value_type;
    if(strings.empty() || strings.front().empty()) {
        output = ConvertType{};
        return true;
    }
    ConvertType val;
    if(lexical_conversion<typename ConvertTo::value_type, typename ConvertTo::value_type>(strings, val)) {
        output = val;
        return true;
    }
    return false;
}

/// Sum a vector of flag representations
/// The flag vector produces a series of strings in a vector,  simple true is represented by a "1",  simple false is
/// by
/// "-1" an if numbers are passed by some fashion they are captured as well so the function just checks for the most
/// common true and false strings then uses stoll to convert the rest for summing
template <typename T, enable_if_t<std::is_unsigned<T>::value, detail::enabler> = detail::dummy>
void sum_flag_vector(const std::vector<std::string> &flags, T &output) {
    std::int64_t count{0};
    for(auto &flag : flags) {
        count += detail::to_flag_value(flag);
    }
    output = (count > 0) ? static_cast<T>(count) : T{0};
}

/// Sum a vector of flag representations
/// The flag vector produces a series of strings in a vector,  simple true is represented by a "1",  simple false is
/// by
/// "-1" an if numbers are passed by some fashion they are captured as well so the function just checks for the most
/// common true and false strings then uses stoll to convert the rest for summing
template <typename T, enable_if_t<std::is_signed<T>::value, detail::enabler> = detail::dummy>
void sum_flag_vector(const std::vector<std::string> &flags, T &output) {
    std::int64_t count{0};
    for(auto &flag : flags) {
        count += detail::to_flag_value(flag);
    }
    output = static_cast<T>(count);
}

#ifdef _MSC_VER
#pragma warning(push)
#pragma warning(disable : 4800)
#endif
// with Atomic<XX> this could produce a warning due to the conversion but if atomic gets here it is an old style so will
// most likely still work

/// Sum a vector of flag representations
/// The flag vector produces a series of strings in a vector,  simple true is represented by a "1",  simple false is
/// by
/// "-1" an if numbers are passed by some fashion they are captured as well so the function just checks for the most
/// common true and false strings then uses stoll to convert the rest for summing
template <typename T,
          enable_if_t<!std::is_signed<T>::value && !std::is_unsigned<T>::value, detail::enabler> = detail::dummy>
void sum_flag_vector(const std::vector<std::string> &flags, T &output) {
    std::int64_t count{0};
    for(auto &flag : flags) {
        count += detail::to_flag_value(flag);
    }
    std::string out = detail::to_string(count);
    lexical_cast(out, output);
}

#ifdef _MSC_VER
#pragma warning(pop)
#endif

}  // namespace detail


namespace detail {

// Returns false if not a short option. Otherwise, sets opt name and rest and returns true
inline bool split_short(const std::string &current, std::string &name, std::string &rest) {
    if(current.size() > 1 && current[0] == '-' && valid_first_char(current[1])) {
        name = current.substr(1, 1);
        rest = current.substr(2);
        return true;
    }
    return false;
}

// Returns false if not a long option. Otherwise, sets opt name and other side of = and returns true
inline bool split_long(const std::string &current, std::string &name, std::string &value) {
    if(current.size() > 2 && current.substr(0, 2) == "--" && valid_first_char(current[2])) {
        auto loc = current.find_first_of('=');
        if(loc != std::string::npos) {
            name = current.substr(2, loc - 2);
            value = current.substr(loc + 1);
        } else {
            name = current.substr(2);
            value = "";
        }
        return true;
    }
    return false;
}

// Returns false if not a windows style option. Otherwise, sets opt name and value and returns true
inline bool split_windows_style(const std::string &current, std::string &name, std::string &value) {
    if(current.size() > 1 && current[0] == '/' && valid_first_char(current[1])) {
        auto loc = current.find_first_of(':');
        if(loc != std::string::npos) {
            name = current.substr(1, loc - 1);
            value = current.substr(loc + 1);
        } else {
            name = current.substr(1);
            value = "";
        }
        return true;
    }
    return false;
}

// Splits a string into multiple long and short names
inline std::vector<std::string> split_names(std::string current) {
    std::vector<std::string> output;
    std::size_t val;
    while((val = current.find(",")) != std::string::npos) {
        output.push_back(trim_copy(current.substr(0, val)));
        current = current.substr(val + 1);
    }
    output.push_back(trim_copy(current));
    return output;
}

/// extract default flag values either {def} or starting with a !
inline std::vector<std::pair<std::string, std::string>> get_default_flag_values(const std::string &str) {
    std::vector<std::string> flags = split_names(str);
    flags.erase(std::remove_if(flags.begin(),
                               flags.end(),
                               [](const std::string &name) {
                                   return ((name.empty()) || (!(((name.find_first_of('{') != std::string::npos) &&
                                                                 (name.back() == '}')) ||
                                                                (name[0] == '!'))));
                               }),
                flags.end());
    std::vector<std::pair<std::string, std::string>> output;
    output.reserve(flags.size());
    for(auto &flag : flags) {
        auto def_start = flag.find_first_of('{');
        std::string defval = "false";
        if((def_start != std::string::npos) && (flag.back() == '}')) {
            defval = flag.substr(def_start + 1);
            defval.pop_back();
            flag.erase(def_start, std::string::npos);
        }
        flag.erase(0, flag.find_first_not_of("-!"));
        output.emplace_back(flag, defval);
    }
    return output;
}

/// Get a vector of short names, one of long names, and a single name
inline std::tuple<std::vector<std::string>, std::vector<std::string>, std::string>
get_names(const std::vector<std::string> &input) {

    std::vector<std::string> short_names;
    std::vector<std::string> long_names;
    std::string pos_name;

    for(std::string name : input) {
        if(name.length() == 0) {
            continue;
        }
        if(name.length() > 1 && name[0] == '-' && name[1] != '-') {
            if(name.length() == 2 && valid_first_char(name[1]))
                short_names.emplace_back(1, name[1]);
            else
                throw BadNameString::OneCharName(name);
        } else if(name.length() > 2 && name.substr(0, 2) == "--") {
            name = name.substr(2);
            if(valid_name_string(name))
                long_names.push_back(name);
            else
                throw BadNameString::BadLongName(name);
        } else if(name == "-" || name == "--") {
            throw BadNameString::DashesOnly(name);
        } else {
            if(pos_name.length() > 0)
                throw BadNameString::MultiPositionalNames(name);
            pos_name = name;
        }
    }

    return std::tuple<std::vector<std::string>, std::vector<std::string>, std::string>(
        short_names, long_names, pos_name);
}

}  // namespace detail


class App;

/// Holds values to load into Options
struct ConfigItem {
    /// This is the list of parents
    std::vector<std::string> parents{};

    /// This is the name
    std::string name{};

    /// Listing of inputs
    std::vector<std::string> inputs{};

    /// The list of parents and name joined by "."
    std::string fullname() const {
        std::vector<std::string> tmp = parents;
        tmp.emplace_back(name);
        return detail::join(tmp, ".");
    }
};

/// This class provides a converter for configuration files.
class Config {
  protected:
    std::vector<ConfigItem> items{};

  public:
    /// Convert an app into a configuration
    virtual std::string to_config(const App *, bool, bool, std::string) const = 0;

    /// Convert a configuration into an app
    virtual std::vector<ConfigItem> from_config(std::istream &) const = 0;

    /// Get a flag value
    virtual std::string to_flag(const ConfigItem &item) const {
        if(item.inputs.size() == 1) {
            return item.inputs.at(0);
        }
        throw ConversionError::TooManyInputsFlag(item.fullname());
    }

    /// Parse a config file, throw an error (ParseError:ConfigParseError or FileError) on failure
    std::vector<ConfigItem> from_file(const std::string &name) {
        std::ifstream input{name};
        if(!input.good())
            throw FileError::Missing(name);

        return from_config(input);
    }

    /// Virtual destructor
    virtual ~Config() = default;
};

/// This converter works with INI/TOML files; to write INI files use ConfigINI
class ConfigBase : public Config {
  protected:
    /// the character used for comments
    char commentChar = '#';
    /// the character used to start an array '\0' is a default to not use
    char arrayStart = '[';
    /// the character used to end an array '\0' is a default to not use
    char arrayEnd = ']';
    /// the character used to separate elements in an array
    char arraySeparator = ',';
    /// the character used separate the name from the value
    char valueDelimiter = '=';
    /// the character to use around strings
    char stringQuote = '"';
    /// the character to use around single characters
    char characterQuote = '\'';

  public:
    std::string
    to_config(const App * /*app*/, bool default_also, bool write_description, std::string prefix) const override;

    std::vector<ConfigItem> from_config(std::istream &input) const override;
    /// Specify the configuration for comment characters
    ConfigBase *comment(char cchar) {
        commentChar = cchar;
        return this;
    }
    /// Specify the start and end characters for an array
    ConfigBase *arrayBounds(char aStart, char aEnd) {
        arrayStart = aStart;
        arrayEnd = aEnd;
        return this;
    }
    /// Specify the delimiter character for an array
    ConfigBase *arrayDelimiter(char aSep) {
        arraySeparator = aSep;
        return this;
    }
    /// Specify the delimiter between a name and value
    ConfigBase *valueSeparator(char vSep) {
        valueDelimiter = vSep;
        return this;
    }
    /// Specify the quote characters used around strings and characters
    ConfigBase *quoteCharacter(char qString, char qChar) {
        stringQuote = qString;
        characterQuote = qChar;
        return this;
    }
};

/// the default Config is the TOML file format
using ConfigTOML = ConfigBase;

/// ConfigINI generates a "standard" INI compliant output
class ConfigINI : public ConfigTOML {

  public:
    ConfigINI() {
        commentChar = ';';
        arrayStart = '\0';
        arrayEnd = '\0';
        arraySeparator = ' ';
        valueDelimiter = '=';
    }
};


class Option;

/// @defgroup validator_group Validators

/// @brief Some validators that are provided
///
/// These are simple `std::string(const std::string&)` validators that are useful. They return
/// a string if the validation fails. A custom struct is provided, as well, with the same user
/// semantics, but with the ability to provide a new type name.
/// @{

///
class Validator {
  protected:
    /// This is the description function, if empty the description_ will be used
    std::function<std::string()> desc_function_{[]() { return std::string{}; }};

    /// This is the base function that is to be called.
    /// Returns a string error message if validation fails.
    std::function<std::string(std::string &)> func_{[](std::string &) { return std::string{}; }};
    /// The name for search purposes of the Validator
    std::string name_{};
    /// A Validator will only apply to an indexed value (-1 is all elements)
    int application_index_ = -1;
    /// Enable for Validator to allow it to be disabled if need be
    bool active_{true};
    /// specify that a validator should not modify the input
    bool non_modifying_{false};

  public:
    Validator() = default;
    /// Construct a Validator with just the description string
    explicit Validator(std::string validator_desc) : desc_function_([validator_desc]() { return validator_desc; }) {}
    /// Construct Validator from basic information
    Validator(std::function<std::string(std::string &)> op, std::string validator_desc, std::string validator_name = "")
        : desc_function_([validator_desc]() { return validator_desc; }), func_(std::move(op)),
          name_(std::move(validator_name)) {}
    /// Set the Validator operation function
    Validator &operation(std::function<std::string(std::string &)> op) {
        func_ = std::move(op);
        return *this;
    }
    /// This is the required operator for a Validator - provided to help
    /// users (CLI11 uses the member `func` directly)
    std::string operator()(std::string &str) const {
        std::string retstring;
        if(active_) {
            if(non_modifying_) {
                std::string value = str;
                retstring = func_(value);
            } else {
                retstring = func_(str);
            }
        }
        return retstring;
    }

    /// This is the required operator for a Validator - provided to help
    /// users (CLI11 uses the member `func` directly)
    std::string operator()(const std::string &str) const {
        std::string value = str;
        return (active_) ? func_(value) : std::string{};
    }

    /// Specify the type string
    Validator &description(std::string validator_desc) {
        desc_function_ = [validator_desc]() { return validator_desc; };
        return *this;
    }
    /// Specify the type string
    Validator description(std::string validator_desc) const {
        Validator newval(*this);
        newval.desc_function_ = [validator_desc]() { return validator_desc; };
        return newval;
    }
    /// Generate type description information for the Validator
    std::string get_description() const {
        if(active_) {
            return desc_function_();
        }
        return std::string{};
    }
    /// Specify the type string
    Validator &name(std::string validator_name) {
        name_ = std::move(validator_name);
        return *this;
    }
    /// Specify the type string
    Validator name(std::string validator_name) const {
        Validator newval(*this);
        newval.name_ = std::move(validator_name);
        return newval;
    }
    /// Get the name of the Validator
    const std::string &get_name() const { return name_; }
    /// Specify whether the Validator is active or not
    Validator &active(bool active_val = true) {
        active_ = active_val;
        return *this;
    }
    /// Specify whether the Validator is active or not
    Validator active(bool active_val = true) const {
        Validator newval(*this);
        newval.active_ = active_val;
        return newval;
    }

    /// Specify whether the Validator can be modifying or not
    Validator &non_modifying(bool no_modify = true) {
        non_modifying_ = no_modify;
        return *this;
    }
    /// Specify the application index of a validator
    Validator &application_index(int app_index) {
        application_index_ = app_index;
        return *this;
    }
    /// Specify the application index of a validator
    Validator application_index(int app_index) const {
        Validator newval(*this);
        newval.application_index_ = app_index;
        return newval;
    }
    /// Get the current value of the application index
    int get_application_index() const { return application_index_; }
    /// Get a boolean if the validator is active
    bool get_active() const { return active_; }

    /// Get a boolean if the validator is allowed to modify the input returns true if it can modify the input
    bool get_modifying() const { return !non_modifying_; }

    /// Combining validators is a new validator. Type comes from left validator if function, otherwise only set if the
    /// same.
    Validator operator&(const Validator &other) const {
        Validator newval;

        newval._merge_description(*this, other, " AND ");

        // Give references (will make a copy in lambda function)
        const std::function<std::string(std::string & filename)> &f1 = func_;
        const std::function<std::string(std::string & filename)> &f2 = other.func_;

        newval.func_ = [f1, f2](std::string &input) {
            std::string s1 = f1(input);
            std::string s2 = f2(input);
            if(!s1.empty() && !s2.empty())
                return std::string("(") + s1 + ") AND (" + s2 + ")";
            else
                return s1 + s2;
        };

        newval.active_ = (active_ & other.active_);
        newval.application_index_ = application_index_;
        return newval;
    }

    /// Combining validators is a new validator. Type comes from left validator if function, otherwise only set if the
    /// same.
    Validator operator|(const Validator &other) const {
        Validator newval;

        newval._merge_description(*this, other, " OR ");

        // Give references (will make a copy in lambda function)
        const std::function<std::string(std::string &)> &f1 = func_;
        const std::function<std::string(std::string &)> &f2 = other.func_;

        newval.func_ = [f1, f2](std::string &input) {
            std::string s1 = f1(input);
            std::string s2 = f2(input);
            if(s1.empty() || s2.empty())
                return std::string();

            return std::string("(") + s1 + ") OR (" + s2 + ")";
        };
        newval.active_ = (active_ & other.active_);
        newval.application_index_ = application_index_;
        return newval;
    }

    /// Create a validator that fails when a given validator succeeds
    Validator operator!() const {
        Validator newval;
        const std::function<std::string()> &dfunc1 = desc_function_;
        newval.desc_function_ = [dfunc1]() {
            auto str = dfunc1();
            return (!str.empty()) ? std::string("NOT ") + str : std::string{};
        };
        // Give references (will make a copy in lambda function)
        const std::function<std::string(std::string & res)> &f1 = func_;

        newval.func_ = [f1, dfunc1](std::string &test) -> std::string {
            std::string s1 = f1(test);
            if(s1.empty()) {
                return std::string("check ") + dfunc1() + " succeeded improperly";
            }
            return std::string{};
        };
        newval.active_ = active_;
        newval.application_index_ = application_index_;
        return newval;
    }

  private:
    void _merge_description(const Validator &val1, const Validator &val2, const std::string &merger) {

        const std::function<std::string()> &dfunc1 = val1.desc_function_;
        const std::function<std::string()> &dfunc2 = val2.desc_function_;

        desc_function_ = [=]() {
            std::string f1 = dfunc1();
            std::string f2 = dfunc2();
            if((f1.empty()) || (f2.empty())) {
                return f1 + f2;
            }
            return std::string(1, '(') + f1 + ')' + merger + '(' + f2 + ')';
        };
    }
};  // namespace CLI

/// Class wrapping some of the accessors of Validator
class CustomValidator : public Validator {
  public:
};
// The implementation of the built in validators is using the Validator class;
// the user is only expected to use the const (static) versions (since there's no setup).
// Therefore, this is in detail.
namespace detail {

/// CLI enumeration of different file types
enum class path_type { nonexistent, file, directory };

#if defined CLI11_HAS_FILESYSTEM && CLI11_HAS_FILESYSTEM > 0
/// get the type of the path from a file name
inline path_type check_path(const char *file) noexcept {
    std::error_code ec;
    auto stat = std::filesystem::status(file, ec);
    if(ec) {
        return path_type::nonexistent;
    }
    switch(stat.type()) {
    case std::filesystem::file_type::none:
    case std::filesystem::file_type::not_found:
        return path_type::nonexistent;
    case std::filesystem::file_type::directory:
        return path_type::directory;
    case std::filesystem::file_type::symlink:
    case std::filesystem::file_type::block:
    case std::filesystem::file_type::character:
    case std::filesystem::file_type::fifo:
    case std::filesystem::file_type::socket:
    case std::filesystem::file_type::regular:
    case std::filesystem::file_type::unknown:
    default:
        return path_type::file;
    }
}
#else
/// get the type of the path from a file name
inline path_type check_path(const char *file) noexcept {
#if defined(_MSC_VER)
    struct __stat64 buffer;
    if(_stat64(file, &buffer) == 0) {
        return ((buffer.st_mode & S_IFDIR) != 0) ? path_type::directory : path_type::file;
    }
#else
    struct stat buffer;
    if(stat(file, &buffer) == 0) {
        return ((buffer.st_mode & S_IFDIR) != 0) ? path_type::directory : path_type::file;
    }
#endif
    return path_type::nonexistent;
}
#endif
/// Check for an existing file (returns error message if check fails)
class ExistingFileValidator : public Validator {
  public:
    ExistingFileValidator() : Validator("FILE") {
        func_ = [](std::string &filename) {
            auto path_result = check_path(filename.c_str());
            if(path_result == path_type::nonexistent) {
                return "File does not exist: " + filename;
            }
            if(path_result == path_type::directory) {
                return "File is actually a directory: " + filename;
            }
            return std::string();
        };
    }
};

/// Check for an existing directory (returns error message if check fails)
class ExistingDirectoryValidator : public Validator {
  public:
    ExistingDirectoryValidator() : Validator("DIR") {
        func_ = [](std::string &filename) {
            auto path_result = check_path(filename.c_str());
            if(path_result == path_type::nonexistent) {
                return "Directory does not exist: " + filename;
            }
            if(path_result == path_type::file) {
                return "Directory is actually a file: " + filename;
            }
            return std::string();
        };
    }
};

/// Check for an existing path
class ExistingPathValidator : public Validator {
  public:
    ExistingPathValidator() : Validator("PATH(existing)") {
        func_ = [](std::string &filename) {
            auto path_result = check_path(filename.c_str());
            if(path_result == path_type::nonexistent) {
                return "Path does not exist: " + filename;
            }
            return std::string();
        };
    }
};

/// Check for an non-existing path
class NonexistentPathValidator : public Validator {
  public:
    NonexistentPathValidator() : Validator("PATH(non-existing)") {
        func_ = [](std::string &filename) {
            auto path_result = check_path(filename.c_str());
            if(path_result != path_type::nonexistent) {
                return "Path already exists: " + filename;
            }
            return std::string();
        };
    }
};

/// Validate the given string is a legal ipv4 address
class IPV4Validator : public Validator {
  public:
    IPV4Validator() : Validator("IPV4") {
        func_ = [](std::string &ip_addr) {
            auto result = CLI::detail::split(ip_addr, '.');
            if(result.size() != 4) {
                return std::string("Invalid IPV4 address must have four parts (") + ip_addr + ')';
            }
            int num;
            for(const auto &var : result) {
                bool retval = detail::lexical_cast(var, num);
                if(!retval) {
                    return std::string("Failed parsing number (") + var + ')';
                }
                if(num < 0 || num > 255) {
                    return std::string("Each IP number must be between 0 and 255 ") + var;
                }
            }
            return std::string();
        };
    }
};

}  // namespace detail

// Static is not needed here, because global const implies static.

/// Check for existing file (returns error message if check fails)
const detail::ExistingFileValidator ExistingFile;

/// Check for an existing directory (returns error message if check fails)
const detail::ExistingDirectoryValidator ExistingDirectory;

/// Check for an existing path
const detail::ExistingPathValidator ExistingPath;

/// Check for an non-existing path
const detail::NonexistentPathValidator NonexistentPath;

/// Check for an IP4 address
const detail::IPV4Validator ValidIPV4;

/// Validate the input as a particular type
template <typename DesiredType> class TypeValidator : public Validator {
  public:
    explicit TypeValidator(const std::string &validator_name) : Validator(validator_name) {
        func_ = [](std::string &input_string) {
            auto val = DesiredType();
            if(!detail::lexical_cast(input_string, val)) {
                return std::string("Failed parsing ") + input_string + " as a " + detail::type_name<DesiredType>();
            }
            return std::string();
        };
    }
    TypeValidator() : TypeValidator(detail::type_name<DesiredType>()) {}
};

/// Check for a number
const TypeValidator<double> Number("NUMBER");

/// Produce a range (factory). Min and max are inclusive.
class Range : public Validator {
  public:
    /// This produces a range with min and max inclusive.
    ///
    /// Note that the constructor is templated, but the struct is not, so C++17 is not
    /// needed to provide nice syntax for Range(a,b).
    template <typename T>
    Range(T min, T max, const std::string &validator_name = std::string{}) : Validator(validator_name) {
        if(validator_name.empty()) {
            std::stringstream out;
            out << detail::type_name<T>() << " in [" << min << " - " << max << "]";
            description(out.str());
        }

        func_ = [min, max](std::string &input) {
            T val;
            bool converted = detail::lexical_cast(input, val);
            if((!converted) || (val < min || val > max))
                return std::string("Value ") + input + " not in range " + std::to_string(min) + " to " +
                       std::to_string(max);

            return std::string();
        };
    }

    /// Range of one value is 0 to value
    template <typename T>
    explicit Range(T max, const std::string &validator_name = std::string{})
        : Range(static_cast<T>(0), max, validator_name) {}
};

/// Check for a non negative number
const Range NonNegativeNumber(std::numeric_limits<double>::max(), "NONNEGATIVE");

/// Check for a positive valued number (val>0.0), min() her is the smallest positive number
const Range PositiveNumber(std::numeric_limits<double>::min(), std::numeric_limits<double>::max(), "POSITIVE");

/// Produce a bounded range (factory). Min and max are inclusive.
class Bound : public Validator {
  public:
    /// This bounds a value with min and max inclusive.
    ///
    /// Note that the constructor is templated, but the struct is not, so C++17 is not
    /// needed to provide nice syntax for Range(a,b).
    template <typename T> Bound(T min, T max) {
        std::stringstream out;
        out << detail::type_name<T>() << " bounded to [" << min << " - " << max << "]";
        description(out.str());

        func_ = [min, max](std::string &input) {
            T val;
            bool converted = detail::lexical_cast(input, val);
            if(!converted) {
                return std::string("Value ") + input + " could not be converted";
            }
            if(val < min)
                input = detail::to_string(min);
            else if(val > max)
                input = detail::to_string(max);

            return std::string{};
        };
    }

    /// Range of one value is 0 to value
    template <typename T> explicit Bound(T max) : Bound(static_cast<T>(0), max) {}
};

namespace detail {
template <typename T,
          enable_if_t<is_copyable_ptr<typename std::remove_reference<T>::type>::value, detail::enabler> = detail::dummy>
auto smart_deref(T value) -> decltype(*value) {
    return *value;
}

template <
    typename T,
    enable_if_t<!is_copyable_ptr<typename std::remove_reference<T>::type>::value, detail::enabler> = detail::dummy>
typename std::remove_reference<T>::type &smart_deref(T &value) {
    return value;
}
/// Generate a string representation of a set
template <typename T> std::string generate_set(const T &set) {
    using element_t = typename detail::element_type<T>::type;
    using iteration_type_t = typename detail::pair_adaptor<element_t>::value_type;  // the type of the object pair
    std::string out(1, '{');
    out.append(detail::join(
        detail::smart_deref(set),
        [](const iteration_type_t &v) { return detail::pair_adaptor<element_t>::first(v); },
        ","));
    out.push_back('}');
    return out;
}

/// Generate a string representation of a map
template <typename T> std::string generate_map(const T &map, bool key_only = false) {
    using element_t = typename detail::element_type<T>::type;
    using iteration_type_t = typename detail::pair_adaptor<element_t>::value_type;  // the type of the object pair
    std::string out(1, '{');
    out.append(detail::join(
        detail::smart_deref(map),
        [key_only](const iteration_type_t &v) {
            std::string res{detail::to_string(detail::pair_adaptor<element_t>::first(v))};

            if(!key_only) {
                res.append("->");
                res += detail::to_string(detail::pair_adaptor<element_t>::second(v));
            }
            return res;
        },
        ","));
    out.push_back('}');
    return out;
}

template <typename C, typename V> struct has_find {
    template <typename CC, typename VV>
    static auto test(int) -> decltype(std::declval<CC>().find(std::declval<VV>()), std::true_type());
    template <typename, typename> static auto test(...) -> decltype(std::false_type());

    static const auto value = decltype(test<C, V>(0))::value;
    using type = std::integral_constant<bool, value>;
};

/// A search function
template <typename T, typename V, enable_if_t<!has_find<T, V>::value, detail::enabler> = detail::dummy>
auto search(const T &set, const V &val) -> std::pair<bool, decltype(std::begin(detail::smart_deref(set)))> {
    using element_t = typename detail::element_type<T>::type;
    auto &setref = detail::smart_deref(set);
    auto it = std::find_if(std::begin(setref), std::end(setref), [&val](decltype(*std::begin(setref)) v) {
        return (detail::pair_adaptor<element_t>::first(v) == val);
    });
    return {(it != std::end(setref)), it};
}

/// A search function that uses the built in find function
template <typename T, typename V, enable_if_t<has_find<T, V>::value, detail::enabler> = detail::dummy>
auto search(const T &set, const V &val) -> std::pair<bool, decltype(std::begin(detail::smart_deref(set)))> {
    auto &setref = detail::smart_deref(set);
    auto it = setref.find(val);
    return {(it != std::end(setref)), it};
}

/// A search function with a filter function
template <typename T, typename V>
auto search(const T &set, const V &val, const std::function<V(V)> &filter_function)
    -> std::pair<bool, decltype(std::begin(detail::smart_deref(set)))> {
    using element_t = typename detail::element_type<T>::type;
    // do the potentially faster first search
    auto res = search(set, val);
    if((res.first) || (!(filter_function))) {
        return res;
    }
    // if we haven't found it do the longer linear search with all the element translations
    auto &setref = detail::smart_deref(set);
    auto it = std::find_if(std::begin(setref), std::end(setref), [&](decltype(*std::begin(setref)) v) {
        V a{detail::pair_adaptor<element_t>::first(v)};
        a = filter_function(a);
        return (a == val);
    });
    return {(it != std::end(setref)), it};
}

// the following suggestion was made by Nikita Ofitserov(@himikof)
// done in templates to prevent compiler warnings on negation of unsigned numbers

/// Do a check for overflow on signed numbers
template <typename T>
inline typename std::enable_if<std::is_signed<T>::value, T>::type overflowCheck(const T &a, const T &b) {
    if((a > 0) == (b > 0)) {
        return ((std::numeric_limits<T>::max)() / (std::abs)(a) < (std::abs)(b));
    } else {
        return ((std::numeric_limits<T>::min)() / (std::abs)(a) > -(std::abs)(b));
    }
}
/// Do a check for overflow on unsigned numbers
template <typename T>
inline typename std::enable_if<!std::is_signed<T>::value, T>::type overflowCheck(const T &a, const T &b) {
    return ((std::numeric_limits<T>::max)() / a < b);
}

/// Performs a *= b; if it doesn't cause integer overflow. Returns false otherwise.
template <typename T> typename std::enable_if<std::is_integral<T>::value, bool>::type checked_multiply(T &a, T b) {
    if(a == 0 || b == 0 || a == 1 || b == 1) {
        a *= b;
        return true;
    }
    if(a == (std::numeric_limits<T>::min)() || b == (std::numeric_limits<T>::min)()) {
        return false;
    }
    if(overflowCheck(a, b)) {
        return false;
    }
    a *= b;
    return true;
}

/// Performs a *= b; if it doesn't equal infinity. Returns false otherwise.
template <typename T>
typename std::enable_if<std::is_floating_point<T>::value, bool>::type checked_multiply(T &a, T b) {
    T c = a * b;
    if(std::isinf(c) && !std::isinf(a) && !std::isinf(b)) {
        return false;
    }
    a = c;
    return true;
}

}  // namespace detail
/// Verify items are in a set
class IsMember : public Validator {
  public:
    using filter_fn_t = std::function<std::string(std::string)>;

    /// This allows in-place construction using an initializer list
    template <typename T, typename... Args>
    IsMember(std::initializer_list<T> values, Args &&... args)
        : IsMember(std::vector<T>(values), std::forward<Args>(args)...) {}

    /// This checks to see if an item is in a set (empty function)
    template <typename T> explicit IsMember(T &&set) : IsMember(std::forward<T>(set), nullptr) {}

    /// This checks to see if an item is in a set: pointer or copy version. You can pass in a function that will filter
    /// both sides of the comparison before computing the comparison.
    template <typename T, typename F> explicit IsMember(T set, F filter_function) {

        // Get the type of the contained item - requires a container have ::value_type
        // if the type does not have first_type and second_type, these are both value_type
        using element_t = typename detail::element_type<T>::type;             // Removes (smart) pointers if needed
        using item_t = typename detail::pair_adaptor<element_t>::first_type;  // Is value_type if not a map

        using local_item_t = typename IsMemberType<item_t>::type;  // This will convert bad types to good ones
                                                                   // (const char * to std::string)

        // Make a local copy of the filter function, using a std::function if not one already
        std::function<local_item_t(local_item_t)> filter_fn = filter_function;

        // This is the type name for help, it will take the current version of the set contents
        desc_function_ = [set]() { return detail::generate_set(detail::smart_deref(set)); };

        // This is the function that validates
        // It stores a copy of the set pointer-like, so shared_ptr will stay alive
        func_ = [set, filter_fn](std::string &input) {
            local_item_t b;
            if(!detail::lexical_cast(input, b)) {
                throw ValidationError(input);  // name is added later
            }
            if(filter_fn) {
                b = filter_fn(b);
            }
            auto res = detail::search(set, b, filter_fn);
            if(res.first) {
                // Make sure the version in the input string is identical to the one in the set
                if(filter_fn) {
                    input = detail::value_string(detail::pair_adaptor<element_t>::first(*(res.second)));
                }

                // Return empty error string (success)
                return std::string{};
            }

            // If you reach this point, the result was not found
            return input + " not in " + detail::generate_set(detail::smart_deref(set));
        };
    }

    /// You can pass in as many filter functions as you like, they nest (string only currently)
    template <typename T, typename... Args>
    IsMember(T &&set, filter_fn_t filter_fn_1, filter_fn_t filter_fn_2, Args &&... other)
        : IsMember(
              std::forward<T>(set),
              [filter_fn_1, filter_fn_2](std::string a) { return filter_fn_2(filter_fn_1(a)); },
              other...) {}
};

/// definition of the default transformation object
template <typename T> using TransformPairs = std::vector<std::pair<std::string, T>>;

/// Translate named items to other or a value set
class Transformer : public Validator {
  public:
    using filter_fn_t = std::function<std::string(std::string)>;

    /// This allows in-place construction
    template <typename... Args>
    Transformer(std::initializer_list<std::pair<std::string, std::string>> values, Args &&... args)
        : Transformer(TransformPairs<std::string>(values), std::forward<Args>(args)...) {}

    /// direct map of std::string to std::string
    template <typename T> explicit Transformer(T &&mapping) : Transformer(std::forward<T>(mapping), nullptr) {}

    /// This checks to see if an item is in a set: pointer or copy version. You can pass in a function that will filter
    /// both sides of the comparison before computing the comparison.
    template <typename T, typename F> explicit Transformer(T mapping, F filter_function) {

        static_assert(detail::pair_adaptor<typename detail::element_type<T>::type>::value,
                      "mapping must produce value pairs");
        // Get the type of the contained item - requires a container have ::value_type
        // if the type does not have first_type and second_type, these are both value_type
        using element_t = typename detail::element_type<T>::type;             // Removes (smart) pointers if needed
        using item_t = typename detail::pair_adaptor<element_t>::first_type;  // Is value_type if not a map
        using local_item_t = typename IsMemberType<item_t>::type;             // Will convert bad types to good ones
                                                                              // (const char * to std::string)

        // Make a local copy of the filter function, using a std::function if not one already
        std::function<local_item_t(local_item_t)> filter_fn = filter_function;

        // This is the type name for help, it will take the current version of the set contents
        desc_function_ = [mapping]() { return detail::generate_map(detail::smart_deref(mapping)); };

        func_ = [mapping, filter_fn](std::string &input) {
            local_item_t b;
            if(!detail::lexical_cast(input, b)) {
                return std::string();
                // there is no possible way we can match anything in the mapping if we can't convert so just return
            }
            if(filter_fn) {
                b = filter_fn(b);
            }
            auto res = detail::search(mapping, b, filter_fn);
            if(res.first) {
                input = detail::value_string(detail::pair_adaptor<element_t>::second(*res.second));
            }
            return std::string{};
        };
    }

    /// You can pass in as many filter functions as you like, they nest
    template <typename T, typename... Args>
    Transformer(T &&mapping, filter_fn_t filter_fn_1, filter_fn_t filter_fn_2, Args &&... other)
        : Transformer(
              std::forward<T>(mapping),
              [filter_fn_1, filter_fn_2](std::string a) { return filter_fn_2(filter_fn_1(a)); },
              other...) {}
};

/// translate named items to other or a value set
class CheckedTransformer : public Validator {
  public:
    using filter_fn_t = std::function<std::string(std::string)>;

    /// This allows in-place construction
    template <typename... Args>
    CheckedTransformer(std::initializer_list<std::pair<std::string, std::string>> values, Args &&... args)
        : CheckedTransformer(TransformPairs<std::string>(values), std::forward<Args>(args)...) {}

    /// direct map of std::string to std::string
    template <typename T> explicit CheckedTransformer(T mapping) : CheckedTransformer(std::move(mapping), nullptr) {}

    /// This checks to see if an item is in a set: pointer or copy version. You can pass in a function that will filter
    /// both sides of the comparison before computing the comparison.
    template <typename T, typename F> explicit CheckedTransformer(T mapping, F filter_function) {

        static_assert(detail::pair_adaptor<typename detail::element_type<T>::type>::value,
                      "mapping must produce value pairs");
        // Get the type of the contained item - requires a container have ::value_type
        // if the type does not have first_type and second_type, these are both value_type
        using element_t = typename detail::element_type<T>::type;             // Removes (smart) pointers if needed
        using item_t = typename detail::pair_adaptor<element_t>::first_type;  // Is value_type if not a map
        using local_item_t = typename IsMemberType<item_t>::type;             // Will convert bad types to good ones
                                                                              // (const char * to std::string)
        using iteration_type_t = typename detail::pair_adaptor<element_t>::value_type;  // the type of the object pair

        // Make a local copy of the filter function, using a std::function if not one already
        std::function<local_item_t(local_item_t)> filter_fn = filter_function;

        auto tfunc = [mapping]() {
            std::string out("value in ");
            out += detail::generate_map(detail::smart_deref(mapping)) + " OR {";
            out += detail::join(
                detail::smart_deref(mapping),
                [](const iteration_type_t &v) { return detail::to_string(detail::pair_adaptor<element_t>::second(v)); },
                ",");
            out.push_back('}');
            return out;
        };

        desc_function_ = tfunc;

        func_ = [mapping, tfunc, filter_fn](std::string &input) {
            local_item_t b;
            bool converted = detail::lexical_cast(input, b);
            if(converted) {
                if(filter_fn) {
                    b = filter_fn(b);
                }
                auto res = detail::search(mapping, b, filter_fn);
                if(res.first) {
                    input = detail::value_string(detail::pair_adaptor<element_t>::second(*res.second));
                    return std::string{};
                }
            }
            for(const auto &v : detail::smart_deref(mapping)) {
                auto output_string = detail::value_string(detail::pair_adaptor<element_t>::second(v));
                if(output_string == input) {
                    return std::string();
                }
            }

            return "Check " + input + " " + tfunc() + " FAILED";
        };
    }

    /// You can pass in as many filter functions as you like, they nest
    template <typename T, typename... Args>
    CheckedTransformer(T &&mapping, filter_fn_t filter_fn_1, filter_fn_t filter_fn_2, Args &&... other)
        : CheckedTransformer(
              std::forward<T>(mapping),
              [filter_fn_1, filter_fn_2](std::string a) { return filter_fn_2(filter_fn_1(a)); },
              other...) {}
};

/// Helper function to allow ignore_case to be passed to IsMember or Transform
inline std::string ignore_case(std::string item) { return detail::to_lower(item); }

/// Helper function to allow ignore_underscore to be passed to IsMember or Transform
inline std::string ignore_underscore(std::string item) { return detail::remove_underscore(item); }

/// Helper function to allow checks to ignore spaces to be passed to IsMember or Transform
inline std::string ignore_space(std::string item) {
    item.erase(std::remove(std::begin(item), std::end(item), ' '), std::end(item));
    item.erase(std::remove(std::begin(item), std::end(item), '\t'), std::end(item));
    return item;
}

/// Multiply a number by a factor using given mapping.
/// Can be used to write transforms for SIZE or DURATION inputs.
///
/// Example:
///   With mapping = `{"b"->1, "kb"->1024, "mb"->1024*1024}`
///   one can recognize inputs like "100", "12kb", "100 MB",
///   that will be automatically transformed to 100, 14448, 104857600.
///
/// Output number type matches the type in the provided mapping.
/// Therefore, if it is required to interpret real inputs like "0.42 s",
/// the mapping should be of a type <string, float> or <string, double>.
class AsNumberWithUnit : public Validator {
  public:
    /// Adjust AsNumberWithUnit behavior.
    /// CASE_SENSITIVE/CASE_INSENSITIVE controls how units are matched.
    /// UNIT_OPTIONAL/UNIT_REQUIRED throws ValidationError
    ///   if UNIT_REQUIRED is set and unit literal is not found.
    enum Options {
        CASE_SENSITIVE = 0,
        CASE_INSENSITIVE = 1,
        UNIT_OPTIONAL = 0,
        UNIT_REQUIRED = 2,
        DEFAULT = CASE_INSENSITIVE | UNIT_OPTIONAL
    };

    template <typename Number>
    explicit AsNumberWithUnit(std::map<std::string, Number> mapping,
                              Options opts = DEFAULT,
                              const std::string &unit_name = "UNIT") {
        description(generate_description<Number>(unit_name, opts));
        validate_mapping(mapping, opts);

        // transform function
        func_ = [mapping, opts](std::string &input) -> std::string {
            Number num;

            detail::rtrim(input);
            if(input.empty()) {
                throw ValidationError("Input is empty");
            }

            // Find split position between number and prefix
            auto unit_begin = input.end();
            while(unit_begin > input.begin() && std::isalpha(*(unit_begin - 1), std::locale())) {
                --unit_begin;
            }

            std::string unit{unit_begin, input.end()};
            input.resize(static_cast<std::size_t>(std::distance(input.begin(), unit_begin)));
            detail::trim(input);

            if(opts & UNIT_REQUIRED && unit.empty()) {
                throw ValidationError("Missing mandatory unit");
            }
            if(opts & CASE_INSENSITIVE) {
                unit = detail::to_lower(unit);
            }
            if(unit.empty()) {
                if(!detail::lexical_cast(input, num)) {
                    throw ValidationError(std::string("Value ") + input + " could not be converted to " +
                                          detail::type_name<Number>());
                }
                // No need to modify input if no unit passed
                return {};
            }

            // find corresponding factor
            auto it = mapping.find(unit);
            if(it == mapping.end()) {
                throw ValidationError(unit +
                                      " unit not recognized. "
                                      "Allowed values: " +
                                      detail::generate_map(mapping, true));
            }

            if(!input.empty()) {
                bool converted = detail::lexical_cast(input, num);
                if(!converted) {
                    throw ValidationError(std::string("Value ") + input + " could not be converted to " +
                                          detail::type_name<Number>());
                }
                // perform safe multiplication
                bool ok = detail::checked_multiply(num, it->second);
                if(!ok) {
                    throw ValidationError(detail::to_string(num) + " multiplied by " + unit +
                                          " factor would cause number overflow. Use smaller value.");
                }
            } else {
                num = static_cast<Number>(it->second);
            }

            input = detail::to_string(num);

            return {};
        };
    }

  private:
    /// Check that mapping contains valid units.
    /// Update mapping for CASE_INSENSITIVE mode.
    template <typename Number> static void validate_mapping(std::map<std::string, Number> &mapping, Options opts) {
        for(auto &kv : mapping) {
            if(kv.first.empty()) {
                throw ValidationError("Unit must not be empty.");
            }
            if(!detail::isalpha(kv.first)) {
                throw ValidationError("Unit must contain only letters.");
            }
        }

        // make all units lowercase if CASE_INSENSITIVE
        if(opts & CASE_INSENSITIVE) {
            std::map<std::string, Number> lower_mapping;
            for(auto &kv : mapping) {
                auto s = detail::to_lower(kv.first);
                if(lower_mapping.count(s)) {
                    throw ValidationError(std::string("Several matching lowercase unit representations are found: ") +
                                          s);
                }
                lower_mapping[detail::to_lower(kv.first)] = kv.second;
            }
            mapping = std::move(lower_mapping);
        }
    }

    /// Generate description like this: NUMBER [UNIT]
    template <typename Number> static std::string generate_description(const std::string &name, Options opts) {
        std::stringstream out;
        out << detail::type_name<Number>() << ' ';
        if(opts & UNIT_REQUIRED) {
            out << name;
        } else {
            out << '[' << name << ']';
        }
        return out.str();
    }
};

/// Converts a human-readable size string (with unit literal) to uin64_t size.
/// Example:
///   "100" => 100
///   "1 b" => 100
///   "10Kb" => 10240 // you can configure this to be interpreted as kilobyte (*1000) or kibibyte (*1024)
///   "10 KB" => 10240
///   "10 kb" => 10240
///   "10 kib" => 10240 // *i, *ib are always interpreted as *bibyte (*1024)
///   "10kb" => 10240
///   "2 MB" => 2097152
///   "2 EiB" => 2^61 // Units up to exibyte are supported
class AsSizeValue : public AsNumberWithUnit {
  public:
    using result_t = std::uint64_t;

    /// If kb_is_1000 is true,
    /// interpret 'kb', 'k' as 1000 and 'kib', 'ki' as 1024
    /// (same applies to higher order units as well).
    /// Otherwise, interpret all literals as factors of 1024.
    /// The first option is formally correct, but
    /// the second interpretation is more wide-spread
    /// (see https://en.wikipedia.org/wiki/Binary_prefix).
    explicit AsSizeValue(bool kb_is_1000) : AsNumberWithUnit(get_mapping(kb_is_1000)) {
        if(kb_is_1000) {
            description("SIZE [b, kb(=1000b), kib(=1024b), ...]");
        } else {
            description("SIZE [b, kb(=1024b), ...]");
        }
    }

  private:
    /// Get <size unit, factor> mapping
    static std::map<std::string, result_t> init_mapping(bool kb_is_1000) {
        std::map<std::string, result_t> m;
        result_t k_factor = kb_is_1000 ? 1000 : 1024;
        result_t ki_factor = 1024;
        result_t k = 1;
        result_t ki = 1;
        m["b"] = 1;
        for(std::string p : {"k", "m", "g", "t", "p", "e"}) {
            k *= k_factor;
            ki *= ki_factor;
            m[p] = k;
            m[p + "b"] = k;
            m[p + "i"] = ki;
            m[p + "ib"] = ki;
        }
        return m;
    }

    /// Cache calculated mapping
    static std::map<std::string, result_t> get_mapping(bool kb_is_1000) {
        if(kb_is_1000) {
            static auto m = init_mapping(true);
            return m;
        } else {
            static auto m = init_mapping(false);
            return m;
        }
    }
};

namespace detail {
/// Split a string into a program name and command line arguments
/// the string is assumed to contain a file name followed by other arguments
/// the return value contains is a pair with the first argument containing the program name and the second
/// everything else.
inline std::pair<std::string, std::string> split_program_name(std::string commandline) {
    // try to determine the programName
    std::pair<std::string, std::string> vals;
    trim(commandline);
    auto esp = commandline.find_first_of(' ', 1);
    while(detail::check_path(commandline.substr(0, esp).c_str()) != path_type::file) {
        esp = commandline.find_first_of(' ', esp + 1);
        if(esp == std::string::npos) {
            // if we have reached the end and haven't found a valid file just assume the first argument is the
            // program name
            if(commandline[0] == '"' || commandline[0] == '\'' || commandline[0] == '`') {
                bool embeddedQuote = false;
                auto keyChar = commandline[0];
                auto end = commandline.find_first_of(keyChar, 1);
                while((end != std::string::npos) && (commandline[end - 1] == '\\')) {  // deal with escaped quotes
                    end = commandline.find_first_of(keyChar, end + 1);
                    embeddedQuote = true;
                }
                if(end != std::string::npos) {
                    vals.first = commandline.substr(1, end - 1);
                    esp = end + 1;
                    if(embeddedQuote) {
                        vals.first = find_and_replace(vals.first, std::string("\\") + keyChar, std::string(1, keyChar));
                        embeddedQuote = false;
                    }
                } else {
                    esp = commandline.find_first_of(' ', 1);
                }
            } else {
                esp = commandline.find_first_of(' ', 1);
            }

            break;
        }
    }
    if(vals.first.empty()) {
        vals.first = commandline.substr(0, esp);
        rtrim(vals.first);
    }

    // strip the program name
    vals.second = (esp != std::string::npos) ? commandline.substr(esp + 1) : std::string{};
    ltrim(vals.second);
    return vals;
}

}  // namespace detail
/// @}


class Option;
class App;

/// This enum signifies the type of help requested
///
/// This is passed in by App; all user classes must accept this as
/// the second argument.

enum class AppFormatMode {
    Normal,  ///< The normal, detailed help
    All,     ///< A fully expanded help
    Sub,     ///< Used when printed as part of expanded subcommand
};

/// This is the minimum requirements to run a formatter.
///
/// A user can subclass this is if they do not care at all
/// about the structure in CLI::Formatter.
class FormatterBase {
  protected:
    /// @name Options
    ///@{

    /// The width of the first column
    std::size_t column_width_{30};

    /// @brief The required help printout labels (user changeable)
    /// Values are Needs, Excludes, etc.
    std::map<std::string, std::string> labels_{};

    ///@}
    /// @name Basic
    ///@{

  public:
    FormatterBase() = default;
    FormatterBase(const FormatterBase &) = default;
    FormatterBase(FormatterBase &&) = default;

    /// Adding a destructor in this form to work around bug in GCC 4.7
    virtual ~FormatterBase() noexcept {}  // NOLINT(modernize-use-equals-default)

    /// This is the key method that puts together help
    virtual std::string make_help(const App *, std::string, AppFormatMode) const = 0;

    ///@}
    /// @name Setters
    ///@{

    /// Set the "REQUIRED" label
    void label(std::string key, std::string val) { labels_[key] = val; }

    /// Set the column width
    void column_width(std::size_t val) { column_width_ = val; }

    ///@}
    /// @name Getters
    ///@{

    /// Get the current value of a name (REQUIRED, etc.)
    std::string get_label(std::string key) const {
        if(labels_.find(key) == labels_.end())
            return key;
        else
            return labels_.at(key);
    }

    /// Get the current column width
    std::size_t get_column_width() const { return column_width_; }

    ///@}
};

/// This is a specialty override for lambda functions
class FormatterLambda final : public FormatterBase {
    using funct_t = std::function<std::string(const App *, std::string, AppFormatMode)>;

    /// The lambda to hold and run
    funct_t lambda_;

  public:
    /// Create a FormatterLambda with a lambda function
    explicit FormatterLambda(funct_t funct) : lambda_(std::move(funct)) {}

    /// Adding a destructor (mostly to make GCC 4.7 happy)
    ~FormatterLambda() noexcept override {}  // NOLINT(modernize-use-equals-default)

    /// This will simply call the lambda function
    std::string make_help(const App *app, std::string name, AppFormatMode mode) const override {
        return lambda_(app, name, mode);
    }
};

/// This is the default Formatter for CLI11. It pretty prints help output, and is broken into quite a few
/// overridable methods, to be highly customizable with minimal effort.
class Formatter : public FormatterBase {
  public:
    Formatter() = default;
    Formatter(const Formatter &) = default;
    Formatter(Formatter &&) = default;

    /// @name Overridables
    ///@{

    /// This prints out a group of options with title
    ///
    virtual std::string make_group(std::string group, bool is_positional, std::vector<const Option *> opts) const;

    /// This prints out just the positionals "group"
    virtual std::string make_positionals(const App *app) const;

    /// This prints out all the groups of options
    std::string make_groups(const App *app, AppFormatMode mode) const;

    /// This prints out all the subcommands
    virtual std::string make_subcommands(const App *app, AppFormatMode mode) const;

    /// This prints out a subcommand
    virtual std::string make_subcommand(const App *sub) const;

    /// This prints out a subcommand in help-all
    virtual std::string make_expanded(const App *sub) const;

    /// This prints out all the groups of options
    virtual std::string make_footer(const App *app) const;

    /// This displays the description line
    virtual std::string make_description(const App *app) const;

    /// This displays the usage line
    virtual std::string make_usage(const App *app, std::string name) const;

    /// This puts everything together
    std::string make_help(const App * /*app*/, std::string, AppFormatMode) const override;

    ///@}
    /// @name Options
    ///@{

    /// This prints out an option help line, either positional or optional form
    virtual std::string make_option(const Option *opt, bool is_positional) const {
        std::stringstream out;
        detail::format_help(
            out, make_option_name(opt, is_positional) + make_option_opts(opt), make_option_desc(opt), column_width_);
        return out.str();
    }

    /// @brief This is the name part of an option, Default: left column
    virtual std::string make_option_name(const Option *, bool) const;

    /// @brief This is the options part of the name, Default: combined into left column
    virtual std::string make_option_opts(const Option *) const;

    /// @brief This is the description. Default: Right column, on new line if left column too large
    virtual std::string make_option_desc(const Option *) const;

    /// @brief This is used to print the name on the USAGE line
    virtual std::string make_option_usage(const Option *opt) const;

    ///@}
};


using results_t = std::vector<std::string>;
/// callback function definition
using callback_t = std::function<bool(const results_t &)>;

class Option;
class App;

using Option_p = std::unique_ptr<Option>;
/// Enumeration of the multiOption Policy selection
enum class MultiOptionPolicy : char {
    Throw,      //!< Throw an error if any extra arguments were given
    TakeLast,   //!< take only the last Expected number of arguments
    TakeFirst,  //!< take only the first Expected number of arguments
    Join,       //!< merge all the arguments together into a single string via the delimiter character default('\n')
    TakeAll     //!< just get all the passed argument regardless
};

/// This is the CRTP base class for Option and OptionDefaults. It was designed this way
/// to share parts of the class; an OptionDefaults can copy to an Option.
template <typename CRTP> class OptionBase {
    friend App;

  protected:
    /// The group membership
    std::string group_ = std::string("Options");

    /// True if this is a required option
    bool required_{false};

    /// Ignore the case when matching (option, not value)
    bool ignore_case_{false};

    /// Ignore underscores when matching (option, not value)
    bool ignore_underscore_{false};

    /// Allow this option to be given in a configuration file
    bool configurable_{true};

    /// Disable overriding flag values with '=value'
    bool disable_flag_override_{false};

    /// Specify a delimiter character for vector arguments
    char delimiter_{'\0'};

    /// Automatically capture default value
    bool always_capture_default_{false};

    /// Policy for handling multiple arguments beyond the expected Max
    MultiOptionPolicy multi_option_policy_{MultiOptionPolicy::Throw};

    /// Copy the contents to another similar class (one based on OptionBase)
    template <typename T> void copy_to(T *other) const {
        other->group(group_);
        other->required(required_);
        other->ignore_case(ignore_case_);
        other->ignore_underscore(ignore_underscore_);
        other->configurable(configurable_);
        other->disable_flag_override(disable_flag_override_);
        other->delimiter(delimiter_);
        other->always_capture_default(always_capture_default_);
        other->multi_option_policy(multi_option_policy_);
    }

  public:
    // setters

    /// Changes the group membership
    CRTP *group(const std::string &name) {
        group_ = name;
        return static_cast<CRTP *>(this);
    }

    /// Set the option as required
    CRTP *required(bool value = true) {
        required_ = value;
        return static_cast<CRTP *>(this);
    }

    /// Support Plumbum term
    CRTP *mandatory(bool value = true) { return required(value); }

    CRTP *always_capture_default(bool value = true) {
        always_capture_default_ = value;
        return static_cast<CRTP *>(this);
    }

    // Getters

    /// Get the group of this option
    const std::string &get_group() const { return group_; }

    /// True if this is a required option
    bool get_required() const { return required_; }

    /// The status of ignore case
    bool get_ignore_case() const { return ignore_case_; }

    /// The status of ignore_underscore
    bool get_ignore_underscore() const { return ignore_underscore_; }

    /// The status of configurable
    bool get_configurable() const { return configurable_; }

    /// The status of configurable
    bool get_disable_flag_override() const { return disable_flag_override_; }

    /// Get the current delimiter char
    char get_delimiter() const { return delimiter_; }

    /// Return true if this will automatically capture the default value for help printing
    bool get_always_capture_default() const { return always_capture_default_; }

    /// The status of the multi option policy
    MultiOptionPolicy get_multi_option_policy() const { return multi_option_policy_; }

    // Shortcuts for multi option policy

    /// Set the multi option policy to take last
    CRTP *take_last() {
        auto self = static_cast<CRTP *>(this);
        self->multi_option_policy(MultiOptionPolicy::TakeLast);
        return self;
    }

    /// Set the multi option policy to take last
    CRTP *take_first() {
        auto self = static_cast<CRTP *>(this);
        self->multi_option_policy(MultiOptionPolicy::TakeFirst);
        return self;
    }

    /// Set the multi option policy to take all arguments
    CRTP *take_all() {
        auto self = static_cast<CRTP *>(this);
        self->multi_option_policy(MultiOptionPolicy::TakeAll);
        return self;
    }

    /// Set the multi option policy to join
    CRTP *join() {
        auto self = static_cast<CRTP *>(this);
        self->multi_option_policy(MultiOptionPolicy::Join);
        return self;
    }

    /// Set the multi option policy to join with a specific delimiter
    CRTP *join(char delim) {
        auto self = static_cast<CRTP *>(this);
        self->delimiter_ = delim;
        self->multi_option_policy(MultiOptionPolicy::Join);
        return self;
    }

    /// Allow in a configuration file
    CRTP *configurable(bool value = true) {
        configurable_ = value;
        return static_cast<CRTP *>(this);
    }

    /// Allow in a configuration file
    CRTP *delimiter(char value = '\0') {
        delimiter_ = value;
        return static_cast<CRTP *>(this);
    }
};

/// This is a version of OptionBase that only supports setting values,
/// for defaults. It is stored as the default option in an App.
class OptionDefaults : public OptionBase<OptionDefaults> {
  public:
    OptionDefaults() = default;

    // Methods here need a different implementation if they are Option vs. OptionDefault

    /// Take the last argument if given multiple times
    OptionDefaults *multi_option_policy(MultiOptionPolicy value = MultiOptionPolicy::Throw) {
        multi_option_policy_ = value;
        return this;
    }

    /// Ignore the case of the option name
    OptionDefaults *ignore_case(bool value = true) {
        ignore_case_ = value;
        return this;
    }

    /// Ignore underscores in the option name
    OptionDefaults *ignore_underscore(bool value = true) {
        ignore_underscore_ = value;
        return this;
    }

    /// Disable overriding flag values with an '=<value>' segment
    OptionDefaults *disable_flag_override(bool value = true) {
        disable_flag_override_ = value;
        return this;
    }

    /// set a delimiter character to split up single arguments to treat as multiple inputs
    OptionDefaults *delimiter(char value = '\0') {
        delimiter_ = value;
        return this;
    }
};

class Option : public OptionBase<Option> {
    friend App;

  protected:
    /// @name Names
    ///@{

    /// A list of the short names (`-a`) without the leading dashes
    std::vector<std::string> snames_{};

    /// A list of the long names (`--long`) without the leading dashes
    std::vector<std::string> lnames_{};

    /// A list of the flag names with the appropriate default value, the first part of the pair should be duplicates of
    /// what is in snames or lnames but will trigger a particular response on a flag
    std::vector<std::pair<std::string, std::string>> default_flag_values_{};

    /// a list of flag names with specified default values;
    std::vector<std::string> fnames_{};

    /// A positional name
    std::string pname_{};

    /// If given, check the environment for this option
    std::string envname_{};

    ///@}
    /// @name Help
    ///@{

    /// The description for help strings
    std::string description_{};

    /// A human readable default value, either manually set, captured, or captured by default
    std::string default_str_{};

    /// If given, replace the text that describes the option type and usage in the help text
    std::string option_text_{};

    /// A human readable type value, set when App creates this
    ///
    /// This is a lambda function so "types" can be dynamic, such as when a set prints its contents.
    std::function<std::string()> type_name_{[]() { return std::string(); }};

    /// Run this function to capture a default (ignore if empty)
    std::function<std::string()> default_function_{};

    ///@}
    /// @name Configuration
    ///@{

    /// The number of arguments that make up one option. max is the nominal type size, min is the minimum number of
    /// strings
    int type_size_max_{1};
    /// The minimum number of arguments an option should be expecting
    int type_size_min_{1};

    /// The minimum number of expected values
    int expected_min_{1};
    /// The maximum number of expected values
    int expected_max_{1};

    /// A list of Validators to run on each value parsed
    std::vector<Validator> validators_{};

    /// A list of options that are required with this option
    std::set<Option *> needs_{};

    /// A list of options that are excluded with this option
    std::set<Option *> excludes_{};

    ///@}
    /// @name Other
    ///@{

    /// link back up to the parent App for fallthrough
    App *parent_{nullptr};

    /// Options store a callback to do all the work
    callback_t callback_{};

    ///@}
    /// @name Parsing results
    ///@{

    /// complete Results of parsing
    results_t results_{};
    /// results after reduction
    results_t proc_results_{};
    /// enumeration for the option state machine
    enum class option_state : char {
        parsing = 0,       //!< The option is currently collecting parsed results
        validated = 2,     //!< the results have been validated
        reduced = 4,       //!< a subset of results has been generated
        callback_run = 6,  //!< the callback has been executed
    };
    /// Whether the callback has run (needed for INI parsing)
    option_state current_option_state_{option_state::parsing};
    /// Specify that extra args beyond type_size_max should be allowed
    bool allow_extra_args_{false};
    /// Specify that the option should act like a flag vs regular option
    bool flag_like_{false};
    /// Control option to run the callback to set the default
    bool run_callback_for_default_{false};
    /// flag indicating a separator needs to be injected after each argument call
    bool inject_separator_{false};
    ///@}

    /// Making an option by hand is not defined, it must be made by the App class
    Option(std::string option_name, std::string option_description, callback_t callback, App *parent)
        : description_(std::move(option_description)), parent_(parent), callback_(std::move(callback)) {
        std::tie(snames_, lnames_, pname_) = detail::get_names(detail::split_names(option_name));
    }

  public:
    /// @name Basic
    ///@{

    Option(const Option &) = delete;
    Option &operator=(const Option &) = delete;

    /// Count the total number of times an option was passed
    std::size_t count() const { return results_.size(); }

    /// True if the option was not passed
    bool empty() const { return results_.empty(); }

    /// This class is true if option is passed.
    explicit operator bool() const { return !empty(); }

    /// Clear the parsed results (mostly for testing)
    void clear() {
        results_.clear();
        current_option_state_ = option_state::parsing;
    }

    ///@}
    /// @name Setting options
    ///@{

    /// Set the number of expected arguments
    Option *expected(int value) {
        if(value < 0) {
            expected_min_ = -value;
            if(expected_max_ < expected_min_) {
                expected_max_ = expected_min_;
            }
            allow_extra_args_ = true;
            flag_like_ = false;
        } else if(value == detail::expected_max_vector_size) {
            expected_min_ = 1;
            expected_max_ = detail::expected_max_vector_size;
            allow_extra_args_ = true;
            flag_like_ = false;
        } else {
            expected_min_ = value;
            expected_max_ = value;
            flag_like_ = (expected_min_ == 0);
        }
        return this;
    }

    /// Set the range of expected arguments
    Option *expected(int value_min, int value_max) {
        if(value_min < 0) {
            value_min = -value_min;
        }

        if(value_max < 0) {
            value_max = detail::expected_max_vector_size;
        }
        if(value_max < value_min) {
            expected_min_ = value_max;
            expected_max_ = value_min;
        } else {
            expected_max_ = value_max;
            expected_min_ = value_min;
        }

        return this;
    }
    /// Set the value of allow_extra_args which allows extra value arguments on the flag or option to be included
    /// with each instance
    Option *allow_extra_args(bool value = true) {
        allow_extra_args_ = value;
        return this;
    }
    /// Get the current value of allow extra args
    bool get_allow_extra_args() const { return allow_extra_args_; }

    /// Set the value of run_callback_for_default which controls whether the callback function should be called to set
    /// the default This is controlled automatically but could be manipulated by the user.
    Option *run_callback_for_default(bool value = true) {
        run_callback_for_default_ = value;
        return this;
    }
    /// Get the current value of run_callback_for_default
    bool get_run_callback_for_default() const { return run_callback_for_default_; }

    /// Adds a Validator with a built in type name
    Option *check(Validator validator, const std::string &validator_name = "") {
        validator.non_modifying();
        validators_.push_back(std::move(validator));
        if(!validator_name.empty())
            validators_.back().name(validator_name);
        return this;
    }

    /// Adds a Validator. Takes a const string& and returns an error message (empty if conversion/check is okay).
    Option *check(std::function<std::string(const std::string &)> Validator,
                  std::string Validator_description = "",
                  std::string Validator_name = "") {
        validators_.emplace_back(Validator, std::move(Validator_description), std::move(Validator_name));
        validators_.back().non_modifying();
        return this;
    }

    /// Adds a transforming Validator with a built in type name
    Option *transform(Validator Validator, const std::string &Validator_name = "") {
        validators_.insert(validators_.begin(), std::move(Validator));
        if(!Validator_name.empty())
            validators_.front().name(Validator_name);
        return this;
    }

    /// Adds a Validator-like function that can change result
    Option *transform(const std::function<std::string(std::string)> &func,
                      std::string transform_description = "",
                      std::string transform_name = "") {
        validators_.insert(validators_.begin(),
                           Validator(
                               [func](std::string &val) {
                                   val = func(val);
                                   return std::string{};
                               },
                               std::move(transform_description),
                               std::move(transform_name)));

        return this;
    }

    /// Adds a user supplied function to run on each item passed in (communicate though lambda capture)
    Option *each(const std::function<void(std::string)> &func) {
        validators_.emplace_back(
            [func](std::string &inout) {
                func(inout);
                return std::string{};
            },
            std::string{});
        return this;
    }
    /// Get a named Validator
    Validator *get_validator(const std::string &Validator_name = "") {
        for(auto &Validator : validators_) {
            if(Validator_name == Validator.get_name()) {
                return &Validator;
            }
        }
        if((Validator_name.empty()) && (!validators_.empty())) {
            return &(validators_.front());
        }
        throw OptionNotFound(std::string{"Validator "} + Validator_name + " Not Found");
    }

    /// Get a Validator by index NOTE: this may not be the order of definition
    Validator *get_validator(int index) {
        // This is an signed int so that it is not equivalent to a pointer.
        if(index >= 0 && index < static_cast<int>(validators_.size())) {
            return &(validators_[static_cast<decltype(validators_)::size_type>(index)]);
        }
        throw OptionNotFound("Validator index is not valid");
    }

    /// Sets required options
    Option *needs(Option *opt) {
        if(opt != this) {
            needs_.insert(opt);
        }
        return this;
    }

    /// Can find a string if needed
    template <typename T = App> Option *needs(std::string opt_name) {
        auto opt = static_cast<T *>(parent_)->get_option_no_throw(opt_name);
        if(opt == nullptr) {
            throw IncorrectConstruction::MissingOption(opt_name);
        }
        return needs(opt);
    }

    /// Any number supported, any mix of string and Opt
    template <typename A, typename B, typename... ARG> Option *needs(A opt, B opt1, ARG... args) {
        needs(opt);
        return needs(opt1, args...);
    }

    /// Remove needs link from an option. Returns true if the option really was in the needs list.
    bool remove_needs(Option *opt) {
        auto iterator = std::find(std::begin(needs_), std::end(needs_), opt);

        if(iterator == std::end(needs_)) {
            return false;
        }
        needs_.erase(iterator);
        return true;
    }

    /// Sets excluded options
    Option *excludes(Option *opt) {
        if(opt == this) {
            throw(IncorrectConstruction("and option cannot exclude itself"));
        }
        excludes_.insert(opt);

        // Help text should be symmetric - excluding a should exclude b
        opt->excludes_.insert(this);

        // Ignoring the insert return value, excluding twice is now allowed.
        // (Mostly to allow both directions to be excluded by user, even though the library does it for you.)

        return this;
    }

    /// Can find a string if needed
    template <typename T = App> Option *excludes(std::string opt_name) {
        auto opt = static_cast<T *>(parent_)->get_option_no_throw(opt_name);
        if(opt == nullptr) {
            throw IncorrectConstruction::MissingOption(opt_name);
        }
        return excludes(opt);
    }

    /// Any number supported, any mix of string and Opt
    template <typename A, typename B, typename... ARG> Option *excludes(A opt, B opt1, ARG... args) {
        excludes(opt);
        return excludes(opt1, args...);
    }

    /// Remove needs link from an option. Returns true if the option really was in the needs list.
    bool remove_excludes(Option *opt) {
        auto iterator = std::find(std::begin(excludes_), std::end(excludes_), opt);

        if(iterator == std::end(excludes_)) {
            return false;
        }
        excludes_.erase(iterator);
        return true;
    }

    /// Sets environment variable to read if no option given
    Option *envname(std::string name) {
        envname_ = std::move(name);
        return this;
    }

    /// Ignore case
    ///
    /// The template hides the fact that we don't have the definition of App yet.
    /// You are never expected to add an argument to the template here.
    template <typename T = App> Option *ignore_case(bool value = true) {
        if(!ignore_case_ && value) {
            ignore_case_ = value;
            auto *parent = static_cast<T *>(parent_);
            for(const Option_p &opt : parent->options_) {
                if(opt.get() == this) {
                    continue;
                }
                auto &omatch = opt->matching_name(*this);
                if(!omatch.empty()) {
                    ignore_case_ = false;
                    throw OptionAlreadyAdded("adding ignore case caused a name conflict with " + omatch);
                }
            }
        } else {
            ignore_case_ = value;
        }
        return this;
    }

    /// Ignore underscores in the option names
    ///
    /// The template hides the fact that we don't have the definition of App yet.
    /// You are never expected to add an argument to the template here.
    template <typename T = App> Option *ignore_underscore(bool value = true) {

        if(!ignore_underscore_ && value) {
            ignore_underscore_ = value;
            auto *parent = static_cast<T *>(parent_);
            for(const Option_p &opt : parent->options_) {
                if(opt.get() == this) {
                    continue;
                }
                auto &omatch = opt->matching_name(*this);
                if(!omatch.empty()) {
                    ignore_underscore_ = false;
                    throw OptionAlreadyAdded("adding ignore underscore caused a name conflict with " + omatch);
                }
            }
        } else {
            ignore_underscore_ = value;
        }
        return this;
    }

    /// Take the last argument if given multiple times (or another policy)
    Option *multi_option_policy(MultiOptionPolicy value = MultiOptionPolicy::Throw) {
        if(value != multi_option_policy_) {
            if(multi_option_policy_ == MultiOptionPolicy::Throw && expected_max_ == detail::expected_max_vector_size &&
               expected_min_ > 1) {  // this bizarre condition is to maintain backwards compatibility
                                     // with the previous behavior of expected_ with vectors
                expected_max_ = expected_min_;
            }
            multi_option_policy_ = value;
            current_option_state_ = option_state::parsing;
        }
        return this;
    }

    /// Disable flag overrides values, e.g. --flag=<value> is not allowed
    Option *disable_flag_override(bool value = true) {
        disable_flag_override_ = value;
        return this;
    }
    ///@}
    /// @name Accessors
    ///@{

    /// The number of arguments the option expects
    int get_type_size() const { return type_size_min_; }

    /// The minimum number of arguments the option expects
    int get_type_size_min() const { return type_size_min_; }
    /// The maximum number of arguments the option expects
    int get_type_size_max() const { return type_size_max_; }

    /// The number of arguments the option expects
    int get_inject_separator() const { return inject_separator_; }

    /// The environment variable associated to this value
    std::string get_envname() const { return envname_; }

    /// The set of options needed
    std::set<Option *> get_needs() const { return needs_; }

    /// The set of options excluded
    std::set<Option *> get_excludes() const { return excludes_; }

    /// The default value (for help printing)
    std::string get_default_str() const { return default_str_; }

    /// Get the callback function
    callback_t get_callback() const { return callback_; }

    /// Get the long names
    const std::vector<std::string> &get_lnames() const { return lnames_; }

    /// Get the short names
    const std::vector<std::string> &get_snames() const { return snames_; }

    /// Get the flag names with specified default values
    const std::vector<std::string> &get_fnames() const { return fnames_; }
    /// Get a single name for the option, first of lname, pname, sname, envname
    const std::string &get_single_name() const {
        if(!lnames_.empty()) {
            return lnames_[0];
        }
        if(!pname_.empty()) {
            return pname_;
        }
        if(!snames_.empty()) {
            return snames_[0];
        }
        return envname_;
    }
    /// The number of times the option expects to be included
    int get_expected() const { return expected_min_; }

    /// The number of times the option expects to be included
    int get_expected_min() const { return expected_min_; }
    /// The max number of times the option expects to be included
    int get_expected_max() const { return expected_max_; }

    /// The total min number of expected  string values to be used
    int get_items_expected_min() const { return type_size_min_ * expected_min_; }

    /// Get the maximum number of items expected to be returned and used for the callback
    int get_items_expected_max() const {
        int t = type_size_max_;
        return detail::checked_multiply(t, expected_max_) ? t : detail::expected_max_vector_size;
    }
    /// The total min number of expected  string values to be used
    int get_items_expected() const { return get_items_expected_min(); }

    /// True if the argument can be given directly
    bool get_positional() const { return pname_.length() > 0; }

    /// True if option has at least one non-positional name
    bool nonpositional() const { return (snames_.size() + lnames_.size()) > 0; }

    /// True if option has description
    bool has_description() const { return description_.length() > 0; }

    /// Get the description
    const std::string &get_description() const { return description_; }

    /// Set the description
    Option *description(std::string option_description) {
        description_ = std::move(option_description);
        return this;
    }

    Option *option_text(std::string text) {
        option_text_ = std::move(text);
        return this;
    }

    const std::string &get_option_text() const { return option_text_; }

    ///@}
    /// @name Help tools
    ///@{

    /// \brief Gets a comma separated list of names.
    /// Will include / prefer the positional name if positional is true.
    /// If all_options is false, pick just the most descriptive name to show.
    /// Use `get_name(true)` to get the positional name (replaces `get_pname`)
    std::string get_name(bool positional = false,  ///< Show the positional name
                         bool all_options = false  ///< Show every option
                         ) const {
        if(get_group().empty())
            return {};  // Hidden

        if(all_options) {

            std::vector<std::string> name_list;

            /// The all list will never include a positional unless asked or that's the only name.
            if((positional && (!pname_.empty())) || (snames_.empty() && lnames_.empty())) {
                name_list.push_back(pname_);
            }
            if((get_items_expected() == 0) && (!fnames_.empty())) {
                for(const std::string &sname : snames_) {
                    name_list.push_back("-" + sname);
                    if(check_fname(sname)) {
                        name_list.back() += "{" + get_flag_value(sname, "") + "}";
                    }
                }

                for(const std::string &lname : lnames_) {
                    name_list.push_back("--" + lname);
                    if(check_fname(lname)) {
                        name_list.back() += "{" + get_flag_value(lname, "") + "}";
                    }
                }
            } else {
                for(const std::string &sname : snames_)
                    name_list.push_back("-" + sname);

                for(const std::string &lname : lnames_)
                    name_list.push_back("--" + lname);
            }

            return detail::join(name_list);
        }

        // This returns the positional name no matter what
        if(positional)
            return pname_;

        // Prefer long name
        if(!lnames_.empty())
            return std::string(2, '-') + lnames_[0];

        // Or short name if no long name
        if(!snames_.empty())
            return std::string(1, '-') + snames_[0];

        // If positional is the only name, it's okay to use that
        return pname_;
    }

    ///@}
    /// @name Parser tools
    ///@{

    /// Process the callback
    void run_callback() {

        if(current_option_state_ == option_state::parsing) {
            _validate_results(results_);
            current_option_state_ = option_state::validated;
        }

        if(current_option_state_ < option_state::reduced) {
            _reduce_results(proc_results_, results_);
            current_option_state_ = option_state::reduced;
        }
        if(current_option_state_ >= option_state::reduced) {
            current_option_state_ = option_state::callback_run;
            if(!(callback_)) {
                return;
            }
            const results_t &send_results = proc_results_.empty() ? results_ : proc_results_;
            bool local_result = callback_(send_results);

            if(!local_result)
                throw ConversionError(get_name(), results_);
        }
    }

    /// If options share any of the same names, find it
    const std::string &matching_name(const Option &other) const {
        static const std::string estring;
        for(const std::string &sname : snames_)
            if(other.check_sname(sname))
                return sname;
        for(const std::string &lname : lnames_)
            if(other.check_lname(lname))
                return lname;

        if(ignore_case_ ||
           ignore_underscore_) {  // We need to do the inverse, in case we are ignore_case or ignore underscore
            for(const std::string &sname : other.snames_)
                if(check_sname(sname))
                    return sname;
            for(const std::string &lname : other.lnames_)
                if(check_lname(lname))
                    return lname;
        }
        return estring;
    }
    /// If options share any of the same names, they are equal (not counting positional)
    bool operator==(const Option &other) const { return !matching_name(other).empty(); }

    /// Check a name. Requires "-" or "--" for short / long, supports positional name
    bool check_name(const std::string &name) const {

        if(name.length() > 2 && name[0] == '-' && name[1] == '-')
            return check_lname(name.substr(2));
        if(name.length() > 1 && name.front() == '-')
            return check_sname(name.substr(1));
        if(!pname_.empty()) {
            std::string local_pname = pname_;
            std::string local_name = name;
            if(ignore_underscore_) {
                local_pname = detail::remove_underscore(local_pname);
                local_name = detail::remove_underscore(local_name);
            }
            if(ignore_case_) {
                local_pname = detail::to_lower(local_pname);
                local_name = detail::to_lower(local_name);
            }
            if(local_name == local_pname) {
                return true;
            }
        }

        if(!envname_.empty()) {
            // this needs to be the original since envname_ shouldn't match on case insensitivity
            return (name == envname_);
        }
        return false;
    }

    /// Requires "-" to be removed from string
    bool check_sname(std::string name) const {
        return (detail::find_member(std::move(name), snames_, ignore_case_) >= 0);
    }

    /// Requires "--" to be removed from string
    bool check_lname(std::string name) const {
        return (detail::find_member(std::move(name), lnames_, ignore_case_, ignore_underscore_) >= 0);
    }

    /// Requires "--" to be removed from string
    bool check_fname(std::string name) const {
        if(fnames_.empty()) {
            return false;
        }
        return (detail::find_member(std::move(name), fnames_, ignore_case_, ignore_underscore_) >= 0);
    }

    /// Get the value that goes for a flag, nominally gets the default value but allows for overrides if not
    /// disabled
    std::string get_flag_value(const std::string &name, std::string input_value) const {
        static const std::string trueString{"true"};
        static const std::string falseString{"false"};
        static const std::string emptyString{"{}"};
        // check for disable flag override_
        if(disable_flag_override_) {
            if(!((input_value.empty()) || (input_value == emptyString))) {
                auto default_ind = detail::find_member(name, fnames_, ignore_case_, ignore_underscore_);
                if(default_ind >= 0) {
                    // We can static cast this to std::size_t because it is more than 0 in this block
                    if(default_flag_values_[static_cast<std::size_t>(default_ind)].second != input_value) {
                        throw(ArgumentMismatch::FlagOverride(name));
                    }
                } else {
                    if(input_value != trueString) {
                        throw(ArgumentMismatch::FlagOverride(name));
                    }
                }
            }
        }
        auto ind = detail::find_member(name, fnames_, ignore_case_, ignore_underscore_);
        if((input_value.empty()) || (input_value == emptyString)) {
            if(flag_like_) {
                return (ind < 0) ? trueString : default_flag_values_[static_cast<std::size_t>(ind)].second;
            } else {
                return (ind < 0) ? default_str_ : default_flag_values_[static_cast<std::size_t>(ind)].second;
            }
        }
        if(ind < 0) {
            return input_value;
        }
        if(default_flag_values_[static_cast<std::size_t>(ind)].second == falseString) {
            try {
                auto val = detail::to_flag_value(input_value);
                return (val == 1) ? falseString : (val == (-1) ? trueString : std::to_string(-val));
            } catch(const std::invalid_argument &) {
                return input_value;
            }
        } else {
            return input_value;
        }
    }

    /// Puts a result at the end
    Option *add_result(std::string s) {
        _add_result(std::move(s), results_);
        current_option_state_ = option_state::parsing;
        return this;
    }

    /// Puts a result at the end and get a count of the number of arguments actually added
    Option *add_result(std::string s, int &results_added) {
        results_added = _add_result(std::move(s), results_);
        current_option_state_ = option_state::parsing;
        return this;
    }

    /// Puts a result at the end
    Option *add_result(std::vector<std::string> s) {
        for(auto &str : s) {
            _add_result(std::move(str), results_);
        }
        current_option_state_ = option_state::parsing;
        return this;
    }

    /// Get the current complete results set
    const results_t &results() const { return results_; }

    /// Get a copy of the results
    results_t reduced_results() const {
        results_t res = proc_results_.empty() ? results_ : proc_results_;
        if(current_option_state_ < option_state::reduced) {
            if(current_option_state_ == option_state::parsing) {
                res = results_;
                _validate_results(res);
            }
            if(!res.empty()) {
                results_t extra;
                _reduce_results(extra, res);
                if(!extra.empty()) {
                    res = std::move(extra);
                }
            }
        }
        return res;
    }

    /// Get the results as a specified type
    template <typename T> void results(T &output) const {
        bool retval;
        if(current_option_state_ >= option_state::reduced || (results_.size() == 1 && validators_.empty())) {
            const results_t &res = (proc_results_.empty()) ? results_ : proc_results_;
            retval = detail::lexical_conversion<T, T>(res, output);
        } else {
            results_t res;
            if(results_.empty()) {
                if(!default_str_.empty()) {
                    // _add_results takes an rvalue only
                    _add_result(std::string(default_str_), res);
                    _validate_results(res);
                    results_t extra;
                    _reduce_results(extra, res);
                    if(!extra.empty()) {
                        res = std::move(extra);
                    }
                } else {
                    res.emplace_back();
                }
            } else {
                res = reduced_results();
            }
            retval = detail::lexical_conversion<T, T>(res, output);
        }
        if(!retval) {
            throw ConversionError(get_name(), results_);
        }
    }

    /// Return the results as the specified type
    template <typename T> T as() const {
        T output;
        results(output);
        return output;
    }

    /// See if the callback has been run already
    bool get_callback_run() const { return (current_option_state_ == option_state::callback_run); }

    ///@}
    /// @name Custom options
    ///@{

    /// Set the type function to run when displayed on this option
    Option *type_name_fn(std::function<std::string()> typefun) {
        type_name_ = std::move(typefun);
        return this;
    }

    /// Set a custom option typestring
    Option *type_name(std::string typeval) {
        type_name_fn([typeval]() { return typeval; });
        return this;
    }

    /// Set a custom option size
    Option *type_size(int option_type_size) {
        if(option_type_size < 0) {
            // this section is included for backwards compatibility
            type_size_max_ = -option_type_size;
            type_size_min_ = -option_type_size;
            expected_max_ = detail::expected_max_vector_size;
        } else {
            type_size_max_ = option_type_size;
            if(type_size_max_ < detail::expected_max_vector_size) {
                type_size_min_ = option_type_size;
            } else {
                inject_separator_ = true;
            }
            if(type_size_max_ == 0)
                required_ = false;
        }
        return this;
    }
    /// Set a custom option type size range
    Option *type_size(int option_type_size_min, int option_type_size_max) {
        if(option_type_size_min < 0 || option_type_size_max < 0) {
            // this section is included for backwards compatibility
            expected_max_ = detail::expected_max_vector_size;
            option_type_size_min = (std::abs)(option_type_size_min);
            option_type_size_max = (std::abs)(option_type_size_max);
        }

        if(option_type_size_min > option_type_size_max) {
            type_size_max_ = option_type_size_min;
            type_size_min_ = option_type_size_max;
        } else {
            type_size_min_ = option_type_size_min;
            type_size_max_ = option_type_size_max;
        }
        if(type_size_max_ == 0) {
            required_ = false;
        }
        if(type_size_max_ >= detail::expected_max_vector_size) {
            inject_separator_ = true;
        }
        return this;
    }

    /// Set the value of the separator injection flag
    void inject_separator(bool value = true) { inject_separator_ = value; }

    /// Set a capture function for the default. Mostly used by App.
    Option *default_function(const std::function<std::string()> &func) {
        default_function_ = func;
        return this;
    }

    /// Capture the default value from the original value (if it can be captured)
    Option *capture_default_str() {
        if(default_function_) {
            default_str_ = default_function_();
        }
        return this;
    }

    /// Set the default value string representation (does not change the contained value)
    Option *default_str(std::string val) {
        default_str_ = std::move(val);
        return this;
    }

    /// Set the default value and validate the results and run the callback if appropriate to set the value into the
    /// bound value only available for types that can be converted to a string
    template <typename X> Option *default_val(const X &val) {
        std::string val_str = detail::to_string(val);
        auto old_option_state = current_option_state_;
        results_t old_results{std::move(results_)};
        results_.clear();
        try {
            add_result(val_str);
            if(run_callback_for_default_) {
                run_callback();  // run callback sets the state we need to reset it again
                current_option_state_ = option_state::parsing;
            } else {
                _validate_results(results_);
                current_option_state_ = old_option_state;
            }
        } catch(const CLI::Error &) {
            // this should be done
            results_ = std::move(old_results);
            current_option_state_ = old_option_state;
            throw;
        }
        results_ = std::move(old_results);
        default_str_ = std::move(val_str);
        return this;
    }

    /// Get the full typename for this option
    std::string get_type_name() const {
        std::string full_type_name = type_name_();
        if(!validators_.empty()) {
            for(auto &Validator : validators_) {
                std::string vtype = Validator.get_description();
                if(!vtype.empty()) {
                    full_type_name += ":" + vtype;
                }
            }
        }
        return full_type_name;
    }

  private:
    /// Run the results through the Validators
    void _validate_results(results_t &res) const {
        // Run the Validators (can change the string)
        if(!validators_.empty()) {
            if(type_size_max_ > 1) {  // in this context index refers to the index in the type
                int index = 0;
                if(get_items_expected_max() < static_cast<int>(res.size()) &&
                   multi_option_policy_ == CLI::MultiOptionPolicy::TakeLast) {
                    // create a negative index for the earliest ones
                    index = get_items_expected_max() - static_cast<int>(res.size());
                }

                for(std::string &result : res) {
                    if(detail::is_separator(result) && type_size_max_ != type_size_min_ && index >= 0) {
                        index = 0;  // reset index for variable size chunks
                        continue;
                    }
                    auto err_msg = _validate(result, (index >= 0) ? (index % type_size_max_) : index);
                    if(!err_msg.empty())
                        throw ValidationError(get_name(), err_msg);
                    ++index;
                }
            } else {
                int index = 0;
                if(expected_max_ < static_cast<int>(res.size()) &&
                   multi_option_policy_ == CLI::MultiOptionPolicy::TakeLast) {
                    // create a negative index for the earliest ones
                    index = expected_max_ - static_cast<int>(res.size());
                }
                for(std::string &result : res) {
                    auto err_msg = _validate(result, index);
                    ++index;
                    if(!err_msg.empty())
                        throw ValidationError(get_name(), err_msg);
                }
            }
        }
    }

    /** reduce the results in accordance with the MultiOptionPolicy
    @param[out] res results are assigned to res if there if they are different
    */
    void _reduce_results(results_t &res, const results_t &original) const {

        // max num items expected or length of vector, always at least 1
        // Only valid for a trimming policy

        res.clear();
        // Operation depends on the policy setting
        switch(multi_option_policy_) {
        case MultiOptionPolicy::TakeAll:
            break;
        case MultiOptionPolicy::TakeLast: {
            // Allow multi-option sizes (including 0)
            std::size_t trim_size = std::min<std::size_t>(
                static_cast<std::size_t>(std::max<int>(get_items_expected_max(), 1)), original.size());
            if(original.size() != trim_size) {
                res.assign(original.end() - static_cast<results_t::difference_type>(trim_size), original.end());
            }
        } break;
        case MultiOptionPolicy::TakeFirst: {
            std::size_t trim_size = std::min<std::size_t>(
                static_cast<std::size_t>(std::max<int>(get_items_expected_max(), 1)), original.size());
            if(original.size() != trim_size) {
                res.assign(original.begin(), original.begin() + static_cast<results_t::difference_type>(trim_size));
            }
        } break;
        case MultiOptionPolicy::Join:
            if(results_.size() > 1) {
                res.push_back(detail::join(original, std::string(1, (delimiter_ == '\0') ? '\n' : delimiter_)));
            }
            break;
        case MultiOptionPolicy::Throw:
        default: {
            auto num_min = static_cast<std::size_t>(get_items_expected_min());
            auto num_max = static_cast<std::size_t>(get_items_expected_max());
            if(num_min == 0) {
                num_min = 1;
            }
            if(num_max == 0) {
                num_max = 1;
            }
            if(original.size() < num_min) {
                throw ArgumentMismatch::AtLeast(get_name(), static_cast<int>(num_min), original.size());
            }
            if(original.size() > num_max) {
                throw ArgumentMismatch::AtMost(get_name(), static_cast<int>(num_max), original.size());
            }
            break;
        }
        }
    }

    // Run a result through the Validators
    std::string _validate(std::string &result, int index) const {
        std::string err_msg;
        if(result.empty() && expected_min_ == 0) {
            // an empty with nothing expected is allowed
            return err_msg;
        }
        for(const auto &vali : validators_) {
            auto v = vali.get_application_index();
            if(v == -1 || v == index) {
                try {
                    err_msg = vali(result);
                } catch(const ValidationError &err) {
                    err_msg = err.what();
                }
                if(!err_msg.empty())
                    break;
            }
        }

        return err_msg;
    }

    /// Add a single result to the result set, taking into account delimiters
    int _add_result(std::string &&result, std::vector<std::string> &res) const {
        int result_count = 0;
        if(allow_extra_args_ && !result.empty() && result.front() == '[' &&
           result.back() == ']') {  // this is now a vector string likely from the default or user entry
            result.pop_back();

            for(auto &var : CLI::detail::split(result.substr(1), ',')) {
                if(!var.empty()) {
                    result_count += _add_result(std::move(var), res);
                }
            }
            return result_count;
        }
        if(delimiter_ == '\0') {
            res.push_back(std::move(result));
            ++result_count;
        } else {
            if((result.find_first_of(delimiter_) != std::string::npos)) {
                for(const auto &var : CLI::detail::split(result, delimiter_)) {
                    if(!var.empty()) {
                        res.push_back(var);
                        ++result_count;
                    }
                }
            } else {
                res.push_back(std::move(result));
                ++result_count;
            }
        }
        return result_count;
    }
};  // namespace CLI


#ifndef CLI11_PARSE
#define CLI11_PARSE(app, argc, argv)                                                                                   \
    try {                                                                                                              \
        (app).parse((argc), (argv));                                                                                   \
    } catch(const CLI::ParseError &e) {                                                                                \
        return (app).exit(e);                                                                                          \
    }
#endif

namespace detail {
enum class Classifier { NONE, POSITIONAL_MARK, SHORT, LONG, WINDOWS_STYLE, SUBCOMMAND, SUBCOMMAND_TERMINATOR };
struct AppFriend;
}  // namespace detail

namespace FailureMessage {
std::string simple(const App *app, const Error &e);
std::string help(const App *app, const Error &e);
}  // namespace FailureMessage

/// enumeration of modes of how to deal with extras in config files

enum class config_extras_mode : char { error = 0, ignore, capture };

class App;

using App_p = std::shared_ptr<App>;

class Option_group;
/// Creates a command line program, with very few defaults.
/** To use, create a new `Program()` instance with `argc`, `argv`, and a help description. The templated
 *  add_option methods make it easy to prepare options. Remember to call `.start` before starting your
 * program, so that the options can be evaluated and the help option doesn't accidentally run your program. */
class App {
    friend Option;
    friend detail::AppFriend;

  protected:
    // This library follows the Google style guide for member names ending in underscores

    /// @name Basics
    ///@{

    /// Subcommand name or program name (from parser if name is empty)
    std::string name_{};

    /// Description of the current program/subcommand
    std::string description_{};

    /// If true, allow extra arguments (ie, don't throw an error). INHERITABLE
    bool allow_extras_{false};

    /// If ignore, allow extra arguments in the ini file (ie, don't throw an error). INHERITABLE
    /// if error error on an extra argument, and if capture feed it to the app
    config_extras_mode allow_config_extras_{config_extras_mode::ignore};

    ///  If true, return immediately on an unrecognized option (implies allow_extras) INHERITABLE
    bool prefix_command_{false};

    /// If set to true the name was automatically generated from the command line vs a user set name
    bool has_automatic_name_{false};

    /// If set to true the subcommand is required to be processed and used, ignored for main app
    bool required_{false};

    /// If set to true the subcommand is disabled and cannot be used, ignored for main app
    bool disabled_{false};

    /// Flag indicating that the pre_parse_callback has been triggered
    bool pre_parse_called_{false};

    /// Flag indicating that the callback for the subcommand should be executed immediately on parse completion which is
    /// before help or ini files are processed. INHERITABLE
    bool immediate_callback_{false};

    /// This is a function that runs prior to the start of parsing
    std::function<void(std::size_t)> pre_parse_callback_{};

    /// This is a function that runs when parsing has finished.
    std::function<void()> parse_complete_callback_{};

    /// This is a function that runs when all processing has completed
    std::function<void()> final_callback_{};

    ///@}
    /// @name Options
    ///@{

    /// The default values for options, customizable and changeable INHERITABLE
    OptionDefaults option_defaults_{};

    /// The list of options, stored locally
    std::vector<Option_p> options_{};

    ///@}
    /// @name Help
    ///@{

    /// Footer to put after all options in the help output INHERITABLE
    std::string footer_{};

    /// This is a function that generates a footer to put after all other options in help output
    std::function<std::string()> footer_callback_{};

    /// A pointer to the help flag if there is one INHERITABLE
    Option *help_ptr_{nullptr};

    /// A pointer to the help all flag if there is one INHERITABLE
    Option *help_all_ptr_{nullptr};

    /// A pointer to a version flag if there is one
    Option *version_ptr_{nullptr};

    /// This is the formatter for help printing. Default provided. INHERITABLE (same pointer)
    std::shared_ptr<FormatterBase> formatter_{new Formatter()};

    /// The error message printing function INHERITABLE
    std::function<std::string(const App *, const Error &e)> failure_message_{FailureMessage::simple};

    ///@}
    /// @name Parsing
    ///@{

    using missing_t = std::vector<std::pair<detail::Classifier, std::string>>;

    /// Pair of classifier, string for missing options. (extra detail is removed on returning from parse)
    ///
    /// This is faster and cleaner than storing just a list of strings and reparsing. This may contain the -- separator.
    missing_t missing_{};

    /// This is a list of pointers to options with the original parse order
    std::vector<Option *> parse_order_{};

    /// This is a list of the subcommands collected, in order
    std::vector<App *> parsed_subcommands_{};

    /// this is a list of subcommands that are exclusionary to this one
    std::set<App *> exclude_subcommands_{};

    /// This is a list of options which are exclusionary to this App, if the options were used this subcommand should
    /// not be
    std::set<Option *> exclude_options_{};

    /// this is a list of subcommands or option groups that are required by this one, the list is not mutual,  the
    /// listed subcommands do not require this one
    std::set<App *> need_subcommands_{};

    /// This is a list of options which are required by this app, the list is not mutual, listed options do not need the
    /// subcommand not be
    std::set<Option *> need_options_{};

    ///@}
    /// @name Subcommands
    ///@{

    /// Storage for subcommand list
    std::vector<App_p> subcommands_{};

    /// If true, the program name is not case sensitive INHERITABLE
    bool ignore_case_{false};

    /// If true, the program should ignore underscores INHERITABLE
    bool ignore_underscore_{false};

    /// Allow subcommand fallthrough, so that parent commands can collect commands after subcommand.  INHERITABLE
    bool fallthrough_{false};

    /// Allow '/' for options for Windows like options. Defaults to true on Windows, false otherwise. INHERITABLE
    bool allow_windows_style_options_{
#ifdef _WIN32
        true
#else
        false
#endif
    };
    /// specify that positional arguments come at the end of the argument sequence not inheritable
    bool positionals_at_end_{false};

    enum class startup_mode : char { stable, enabled, disabled };
    /// specify the startup mode for the app
    /// stable=no change, enabled= startup enabled, disabled=startup disabled
    startup_mode default_startup{startup_mode::stable};

    /// if set to true the subcommand can be triggered via configuration files INHERITABLE
    bool configurable_{false};

    /// If set to true positional options are validated before assigning INHERITABLE
    bool validate_positionals_{false};

    /// indicator that the subcommand is silent and won't show up in subcommands list
    /// This is potentially useful as a modifier subcommand
    bool silent_{false};

    /// Counts the number of times this command/subcommand was parsed
    std::uint32_t parsed_{0U};

    /// Minimum required subcommands (not inheritable!)
    std::size_t require_subcommand_min_{0};

    /// Max number of subcommands allowed (parsing stops after this number). 0 is unlimited INHERITABLE
    std::size_t require_subcommand_max_{0};

    /// Minimum required options (not inheritable!)
    std::size_t require_option_min_{0};

    /// Max number of options allowed. 0 is unlimited (not inheritable)
    std::size_t require_option_max_{0};

    /// A pointer to the parent if this is a subcommand
    App *parent_{nullptr};

    /// The group membership INHERITABLE
    std::string group_{"Subcommands"};

    /// Alias names for the subcommand
    std::vector<std::string> aliases_{};

    ///@}
    /// @name Config
    ///@{

    /// Pointer to the config option
    Option *config_ptr_{nullptr};

    /// This is the formatter for help printing. Default provided. INHERITABLE (same pointer)
    std::shared_ptr<Config> config_formatter_{new ConfigTOML()};

    ///@}

    /// Special private constructor for subcommand
    App(std::string app_description, std::string app_name, App *parent)
        : name_(std::move(app_name)), description_(std::move(app_description)), parent_(parent) {
        // Inherit if not from a nullptr
        if(parent_ != nullptr) {
            if(parent_->help_ptr_ != nullptr)
                set_help_flag(parent_->help_ptr_->get_name(false, true), parent_->help_ptr_->get_description());
            if(parent_->help_all_ptr_ != nullptr)
                set_help_all_flag(parent_->help_all_ptr_->get_name(false, true),
                                  parent_->help_all_ptr_->get_description());

            /// OptionDefaults
            option_defaults_ = parent_->option_defaults_;

            // INHERITABLE
            failure_message_ = parent_->failure_message_;
            allow_extras_ = parent_->allow_extras_;
            allow_config_extras_ = parent_->allow_config_extras_;
            prefix_command_ = parent_->prefix_command_;
            immediate_callback_ = parent_->immediate_callback_;
            ignore_case_ = parent_->ignore_case_;
            ignore_underscore_ = parent_->ignore_underscore_;
            fallthrough_ = parent_->fallthrough_;
            validate_positionals_ = parent_->validate_positionals_;
            configurable_ = parent_->configurable_;
            allow_windows_style_options_ = parent_->allow_windows_style_options_;
            group_ = parent_->group_;
            footer_ = parent_->footer_;
            formatter_ = parent_->formatter_;
            config_formatter_ = parent_->config_formatter_;
            require_subcommand_max_ = parent_->require_subcommand_max_;
        }
    }

  public:
    /// @name Basic
    ///@{

    /// Create a new program. Pass in the same arguments as main(), along with a help string.
    explicit App(std::string app_description = "", std::string app_name = "")
        : App(app_description, app_name, nullptr) {
        set_help_flag("-h,--help", "Print this help message and exit");
    }

    App(const App &) = delete;
    App &operator=(const App &) = delete;

    /// virtual destructor
    virtual ~App() = default;

    /// Set a callback for execution when all parsing and processing has completed
    ///
    /// Due to a bug in c++11,
    /// it is not possible to overload on std::function (fixed in c++14
    /// and backported to c++11 on newer compilers). Use capture by reference
    /// to get a pointer to App if needed.
    App *callback(std::function<void()> app_callback) {
        if(immediate_callback_) {
            parse_complete_callback_ = std::move(app_callback);
        } else {
            final_callback_ = std::move(app_callback);
        }
        return this;
    }

    /// Set a callback for execution when all parsing and processing has completed
    /// aliased as callback
    App *final_callback(std::function<void()> app_callback) {
        final_callback_ = std::move(app_callback);
        return this;
    }

    /// Set a callback to execute when parsing has completed for the app
    ///
    App *parse_complete_callback(std::function<void()> pc_callback) {
        parse_complete_callback_ = std::move(pc_callback);
        return this;
    }

    /// Set a callback to execute prior to parsing.
    ///
    App *preparse_callback(std::function<void(std::size_t)> pp_callback) {
        pre_parse_callback_ = std::move(pp_callback);
        return this;
    }

    /// Set a name for the app (empty will use parser to set the name)
    App *name(std::string app_name = "") {

        if(parent_ != nullptr) {
            auto oname = name_;
            name_ = app_name;
            auto &res = _compare_subcommand_names(*this, *_get_fallthrough_parent());
            if(!res.empty()) {
                name_ = oname;
                throw(OptionAlreadyAdded(app_name + " conflicts with existing subcommand names"));
            }
        } else {
            name_ = app_name;
        }
        has_automatic_name_ = false;
        return this;
    }

    /// Set an alias for the app
    App *alias(std::string app_name) {
        if(!detail::valid_name_string(app_name)) {
            if(app_name.empty()) {
                throw IncorrectConstruction("Empty aliases are not allowed");
            }
            if(!detail::valid_first_char(app_name[0])) {
                throw IncorrectConstruction(
                    "Alias starts with invalid character, allowed characters are [a-zA-z0-9]+'_','?','@' ");
            }
            for(auto c : app_name) {
                if(!detail::valid_later_char(c)) {
                    throw IncorrectConstruction(std::string("Alias contains invalid character ('") + c +
                                                "'), allowed characters are "
                                                "[a-zA-z0-9]+'_','?','@','.','-' ");
                }
            }
        }

        if(parent_ != nullptr) {
            aliases_.push_back(app_name);
            auto &res = _compare_subcommand_names(*this, *_get_fallthrough_parent());
            if(!res.empty()) {
                aliases_.pop_back();
                throw(OptionAlreadyAdded("alias already matches an existing subcommand: " + app_name));
            }
        } else {
            aliases_.push_back(app_name);
        }

        return this;
    }

    /// Remove the error when extras are left over on the command line.
    App *allow_extras(bool allow = true) {
        allow_extras_ = allow;
        return this;
    }

    /// Remove the error when extras are left over on the command line.
    App *required(bool require = true) {
        required_ = require;
        return this;
    }

    /// Disable the subcommand or option group
    App *disabled(bool disable = true) {
        disabled_ = disable;
        return this;
    }

    /// silence the subcommand from showing up in the processed list
    App *silent(bool silence = true) {
        silent_ = silence;
        return this;
    }

    /// Set the subcommand to be disabled by default, so on clear(), at the start of each parse it is disabled
    App *disabled_by_default(bool disable = true) {
        if(disable) {
            default_startup = startup_mode::disabled;
        } else {
            default_startup = (default_startup == startup_mode::enabled) ? startup_mode::enabled : startup_mode::stable;
        }
        return this;
    }

    /// Set the subcommand to be enabled by default, so on clear(), at the start of each parse it is enabled (not
    /// disabled)
    App *enabled_by_default(bool enable = true) {
        if(enable) {
            default_startup = startup_mode::enabled;
        } else {
            default_startup =
                (default_startup == startup_mode::disabled) ? startup_mode::disabled : startup_mode::stable;
        }
        return this;
    }

    /// Set the subcommand callback to be executed immediately on subcommand completion
    App *immediate_callback(bool immediate = true) {
        immediate_callback_ = immediate;
        if(immediate_callback_) {
            if(final_callback_ && !(parse_complete_callback_)) {
                std::swap(final_callback_, parse_complete_callback_);
            }
        } else if(!(final_callback_) && parse_complete_callback_) {
            std::swap(final_callback_, parse_complete_callback_);
        }
        return this;
    }

    /// Set the subcommand to validate positional arguments before assigning
    App *validate_positionals(bool validate = true) {
        validate_positionals_ = validate;
        return this;
    }

    /// ignore extras in config files
    App *allow_config_extras(bool allow = true) {
        if(allow) {
            allow_config_extras_ = config_extras_mode::capture;
            allow_extras_ = true;
        } else {
            allow_config_extras_ = config_extras_mode::error;
        }
        return this;
    }

    /// ignore extras in config files
    App *allow_config_extras(config_extras_mode mode) {
        allow_config_extras_ = mode;
        return this;
    }

    /// Do not parse anything after the first unrecognized option and return
    App *prefix_command(bool allow = true) {
        prefix_command_ = allow;
        return this;
    }

    /// Ignore case. Subcommands inherit value.
    App *ignore_case(bool value = true) {
        if(value && !ignore_case_) {
            ignore_case_ = true;
            auto *p = (parent_ != nullptr) ? _get_fallthrough_parent() : this;
            auto &match = _compare_subcommand_names(*this, *p);
            if(!match.empty()) {
                ignore_case_ = false;  // we are throwing so need to be exception invariant
                throw OptionAlreadyAdded("ignore case would cause subcommand name conflicts: " + match);
            }
        }
        ignore_case_ = value;
        return this;
    }

    /// Allow windows style options, such as `/opt`. First matching short or long name used. Subcommands inherit
    /// value.
    App *allow_windows_style_options(bool value = true) {
        allow_windows_style_options_ = value;
        return this;
    }

    /// Specify that the positional arguments are only at the end of the sequence
    App *positionals_at_end(bool value = true) {
        positionals_at_end_ = value;
        return this;
    }

    /// Specify that the subcommand can be triggered by a config file
    App *configurable(bool value = true) {
        configurable_ = value;
        return this;
    }

    /// Ignore underscore. Subcommands inherit value.
    App *ignore_underscore(bool value = true) {
        if(value && !ignore_underscore_) {
            ignore_underscore_ = true;
            auto *p = (parent_ != nullptr) ? _get_fallthrough_parent() : this;
            auto &match = _compare_subcommand_names(*this, *p);
            if(!match.empty()) {
                ignore_underscore_ = false;
                throw OptionAlreadyAdded("ignore underscore would cause subcommand name conflicts: " + match);
            }
        }
        ignore_underscore_ = value;
        return this;
    }

    /// Set the help formatter
    App *formatter(std::shared_ptr<FormatterBase> fmt) {
        formatter_ = fmt;
        return this;
    }

    /// Set the help formatter
    App *formatter_fn(std::function<std::string(const App *, std::string, AppFormatMode)> fmt) {
        formatter_ = std::make_shared<FormatterLambda>(fmt);
        return this;
    }

    /// Set the config formatter
    App *config_formatter(std::shared_ptr<Config> fmt) {
        config_formatter_ = fmt;
        return this;
    }

    /// Check to see if this subcommand was parsed, true only if received on command line.
    bool parsed() const { return parsed_ > 0; }

    /// Get the OptionDefault object, to set option defaults
    OptionDefaults *option_defaults() { return &option_defaults_; }

    ///@}
    /// @name Adding options
    ///@{

    /// Add an option, will automatically understand the type for common types.
    ///
    /// To use, create a variable with the expected type, and pass it in after the name.
    /// After start is called, you can use count to see if the value was passed, and
    /// the value will be initialized properly. Numbers, vectors, and strings are supported.
    ///
    /// ->required(), ->default, and the validators are options,
    /// The positional options take an optional number of arguments.
    ///
    /// For example,
    ///
    ///     std::string filename;
    ///     program.add_option("filename", filename, "description of filename");
    ///
    Option *add_option(std::string option_name,
                       callback_t option_callback,
                       std::string option_description = "",
                       bool defaulted = false,
                       std::function<std::string()> func = {}) {
        Option myopt{option_name, option_description, option_callback, this};

        if(std::find_if(std::begin(options_), std::end(options_), [&myopt](const Option_p &v) {
               return *v == myopt;
           }) == std::end(options_)) {
            options_.emplace_back();
            Option_p &option = options_.back();
            option.reset(new Option(option_name, option_description, option_callback, this));

            // Set the default string capture function
            option->default_function(func);

            // For compatibility with CLI11 1.7 and before, capture the default string here
            if(defaulted)
                option->capture_default_str();

            // Transfer defaults to the new option
            option_defaults_.copy_to(option.get());

            // Don't bother to capture if we already did
            if(!defaulted && option->get_always_capture_default())
                option->capture_default_str();

            return option.get();
        }
        // we know something matches now find what it is so we can produce more error information
        for(auto &opt : options_) {
            auto &matchname = opt->matching_name(myopt);
            if(!matchname.empty()) {
                throw(OptionAlreadyAdded("added option matched existing option name: " + matchname));
            }
        }
        // this line should not be reached the above loop should trigger the throw
        throw(OptionAlreadyAdded("added option matched existing option name"));  // LCOV_EXCL_LINE
    }

    /// Add option for assigning to a variable
    template <typename AssignTo,
              typename ConvertTo = AssignTo,
              enable_if_t<!std::is_const<ConvertTo>::value, detail::enabler> = detail::dummy>
    Option *add_option(std::string option_name,
                       AssignTo &variable,  ///< The variable to set
                       std::string option_description = "") {

        auto fun = [&variable](const CLI::results_t &res) {  // comment for spacing
            return detail::lexical_conversion<AssignTo, ConvertTo>(res, variable);
        };

        Option *opt = add_option(option_name, fun, option_description, false, [&variable]() {
            return CLI::detail::checked_to_string<AssignTo, ConvertTo>(variable);
        });
        opt->type_name(detail::type_name<ConvertTo>());
        // these must be actual lvalues since (std::max) sometimes is defined in terms of references and references
        // to structs used in the evaluation can be temporary so that would cause issues.
        auto Tcount = detail::type_count<AssignTo>::value;
        auto XCcount = detail::type_count<ConvertTo>::value;
        opt->type_size(detail::type_count_min<ConvertTo>::value, (std::max)(Tcount, XCcount));
        opt->expected(detail::expected_count<ConvertTo>::value);
        opt->run_callback_for_default();
        return opt;
    }

    /// Add option for assigning to a variable
    template <typename AssignTo, enable_if_t<!std::is_const<AssignTo>::value, detail::enabler> = detail::dummy>
    Option *add_option_no_stream(std::string option_name,
                                 AssignTo &variable,  ///< The variable to set
                                 std::string option_description = "") {

        auto fun = [&variable](const CLI::results_t &res) {  // comment for spacing
            return detail::lexical_conversion<AssignTo, AssignTo>(res, variable);
        };

        Option *opt = add_option(option_name, fun, option_description, false, []() { return std::string{}; });
        opt->type_name(detail::type_name<AssignTo>());
        opt->type_size(detail::type_count_min<AssignTo>::value, detail::type_count<AssignTo>::value);
        opt->expected(detail::expected_count<AssignTo>::value);
        opt->run_callback_for_default();
        return opt;
    }

    /// Add option for a callback of a specific type
    template <typename ArgType>
    Option *add_option_function(std::string option_name,
                                const std::function<void(const ArgType &)> &func,  ///< the callback to execute
                                std::string option_description = "") {

        auto fun = [func](const CLI::results_t &res) {
            ArgType variable;
            bool result = detail::lexical_conversion<ArgType, ArgType>(res, variable);
            if(result) {
                func(variable);
            }
            return result;
        };

        Option *opt = add_option(option_name, std::move(fun), option_description, false);
        opt->type_name(detail::type_name<ArgType>());
        opt->type_size(detail::type_count_min<ArgType>::value, detail::type_count<ArgType>::value);
        opt->expected(detail::expected_count<ArgType>::value);
        return opt;
    }

    /// Add option with no description or variable assignment
    Option *add_option(std::string option_name) {
        return add_option(option_name, CLI::callback_t{}, std::string{}, false);
    }

    /// Add option with description but with no variable assignment or callback
    template <typename T,
              enable_if_t<std::is_const<T>::value && std::is_constructible<std::string, T>::value, detail::enabler> =
                  detail::dummy>
    Option *add_option(std::string option_name, T &option_description) {
        return add_option(option_name, CLI::callback_t(), option_description, false);
    }

    /// Set a help flag, replace the existing one if present
    Option *set_help_flag(std::string flag_name = "", const std::string &help_description = "") {
        // take flag_description by const reference otherwise add_flag tries to assign to help_description
        if(help_ptr_ != nullptr) {
            remove_option(help_ptr_);
            help_ptr_ = nullptr;
        }

        // Empty name will simply remove the help flag
        if(!flag_name.empty()) {
            help_ptr_ = add_flag(flag_name, help_description);
            help_ptr_->configurable(false);
        }

        return help_ptr_;
    }

    /// Set a help all flag, replaced the existing one if present
    Option *set_help_all_flag(std::string help_name = "", const std::string &help_description = "") {
        // take flag_description by const reference otherwise add_flag tries to assign to flag_description
        if(help_all_ptr_ != nullptr) {
            remove_option(help_all_ptr_);
            help_all_ptr_ = nullptr;
        }

        // Empty name will simply remove the help all flag
        if(!help_name.empty()) {
            help_all_ptr_ = add_flag(help_name, help_description);
            help_all_ptr_->configurable(false);
        }

        return help_all_ptr_;
    }

    /// Set a version flag and version display string, replace the existing one if present
    Option *set_version_flag(std::string flag_name = "",
                             const std::string &versionString = "",
                             const std::string &version_help = "Display program version information and exit") {
        // take flag_description by const reference otherwise add_flag tries to assign to version_description
        if(version_ptr_ != nullptr) {
            remove_option(version_ptr_);
            version_ptr_ = nullptr;
        }

        // Empty name will simply remove the version flag
        if(!flag_name.empty()) {
            version_ptr_ = add_flag_callback(
                flag_name, [versionString]() { throw(CLI::CallForVersion(versionString, 0)); }, version_help);
            version_ptr_->configurable(false);
        }

        return version_ptr_;
    }
    /// Generate the version string through a callback function
    Option *set_version_flag(std::string flag_name,
                             std::function<std::string()> vfunc,
                             const std::string &version_help = "Display program version information and exit") {
        if(version_ptr_ != nullptr) {
            remove_option(version_ptr_);
            version_ptr_ = nullptr;
        }

        // Empty name will simply remove the version flag
        if(!flag_name.empty()) {
            version_ptr_ = add_flag_callback(
                flag_name, [vfunc]() { throw(CLI::CallForVersion(vfunc(), 0)); }, version_help);
            version_ptr_->configurable(false);
        }

        return version_ptr_;
    }

  private:
    /// Internal function for adding a flag
    Option *_add_flag_internal(std::string flag_name, CLI::callback_t fun, std::string flag_description) {
        Option *opt;
        if(detail::has_default_flag_values(flag_name)) {
            // check for default values and if it has them
            auto flag_defaults = detail::get_default_flag_values(flag_name);
            detail::remove_default_flag_values(flag_name);
            opt = add_option(std::move(flag_name), std::move(fun), std::move(flag_description), false);
            for(const auto &fname : flag_defaults)
                opt->fnames_.push_back(fname.first);
            opt->default_flag_values_ = std::move(flag_defaults);
        } else {
            opt = add_option(std::move(flag_name), std::move(fun), std::move(flag_description), false);
        }
        // flags cannot have positional values
        if(opt->get_positional()) {
            auto pos_name = opt->get_name(true);
            remove_option(opt);
            throw IncorrectConstruction::PositionalFlag(pos_name);
        }
        opt->multi_option_policy(MultiOptionPolicy::TakeLast);
        opt->expected(0);
        opt->required(false);
        return opt;
    }

  public:
    /// Add a flag with no description or variable assignment
    Option *add_flag(std::string flag_name) { return _add_flag_internal(flag_name, CLI::callback_t(), std::string{}); }

    /// Add flag with description but with no variable assignment or callback
    /// takes a constant string,  if a variable string is passed that variable will be assigned the results from the
    /// flag
    template <typename T,
              enable_if_t<std::is_const<T>::value && std::is_constructible<std::string, T>::value, detail::enabler> =
                  detail::dummy>
    Option *add_flag(std::string flag_name, T &flag_description) {
        return _add_flag_internal(flag_name, CLI::callback_t(), flag_description);
    }

    /// Add option for flag with integer result - defaults to allowing multiple passings, but can be forced to one
    /// if `multi_option_policy(CLI::MultiOptionPolicy::Throw)` is used.
    template <typename T,
              enable_if_t<std::is_constructible<T, std::int64_t>::value && !is_bool<T>::value, detail::enabler> =
                  detail::dummy>
    Option *add_flag(std::string flag_name,
                     T &flag_count,  ///< A variable holding the count
                     std::string flag_description = "") {
        flag_count = 0;
        CLI::callback_t fun = [&flag_count](const CLI::results_t &res) {
            try {
                detail::sum_flag_vector(res, flag_count);
            } catch(const std::invalid_argument &) {
                return false;
            }
            return true;
        };
        return _add_flag_internal(flag_name, std::move(fun), std::move(flag_description))
            ->multi_option_policy(MultiOptionPolicy::TakeAll);
    }

    /// Other type version accepts all other types that are not vectors such as bool, enum, string or other classes
    /// that can be converted from a string
    template <typename T,
              enable_if_t<!detail::is_mutable_container<T>::value && !std::is_const<T>::value &&
                              (!std::is_constructible<T, std::int64_t>::value || is_bool<T>::value) &&
                              !std::is_constructible<std::function<void(int)>, T>::value,
                          detail::enabler> = detail::dummy>
    Option *add_flag(std::string flag_name,
                     T &flag_result,  ///< A variable holding true if passed
                     std::string flag_description = "") {

        CLI::callback_t fun = [&flag_result](const CLI::results_t &res) {
            return CLI::detail::lexical_cast(res[0], flag_result);
        };
        return _add_flag_internal(flag_name, std::move(fun), std::move(flag_description))->run_callback_for_default();
    }

    /// Vector version to capture multiple flags.
    template <typename T,
              enable_if_t<!std::is_assignable<std::function<void(std::int64_t)> &, T>::value, detail::enabler> =
                  detail::dummy>
    Option *add_flag(std::string flag_name,
                     std::vector<T> &flag_results,  ///< A vector of values with the flag results
                     std::string flag_description = "") {
        CLI::callback_t fun = [&flag_results](const CLI::results_t &res) {
            bool retval = true;
            for(const auto &elem : res) {
                flag_results.emplace_back();
                retval &= detail::lexical_cast(elem, flag_results.back());
            }
            return retval;
        };
        return _add_flag_internal(flag_name, std::move(fun), std::move(flag_description))
            ->multi_option_policy(MultiOptionPolicy::TakeAll)
            ->run_callback_for_default();
    }

    /// Add option for callback that is triggered with a true flag and takes no arguments
    Option *add_flag_callback(std::string flag_name,
                              std::function<void(void)> function,  ///< A function to call, void(void)
                              std::string flag_description = "") {

        CLI::callback_t fun = [function](const CLI::results_t &res) {
            bool trigger{false};
            auto result = CLI::detail::lexical_cast(res[0], trigger);
            if(result && trigger) {
                function();
            }
            return result;
        };
        return _add_flag_internal(flag_name, std::move(fun), std::move(flag_description));
    }

    /// Add option for callback with an integer value
    Option *add_flag_function(std::string flag_name,
                              std::function<void(std::int64_t)> function,  ///< A function to call, void(int)
                              std::string flag_description = "") {

        CLI::callback_t fun = [function](const CLI::results_t &res) {
            std::int64_t flag_count = 0;
            detail::sum_flag_vector(res, flag_count);
            function(flag_count);
            return true;
        };
        return _add_flag_internal(flag_name, std::move(fun), std::move(flag_description))
            ->multi_option_policy(MultiOptionPolicy::TakeAll);
    }

#ifdef CLI11_CPP14
    /// Add option for callback (C++14 or better only)
    Option *add_flag(std::string flag_name,
                     std::function<void(std::int64_t)> function,  ///< A function to call, void(std::int64_t)
                     std::string flag_description = "") {
        return add_flag_function(std::move(flag_name), std::move(function), std::move(flag_description));
    }
#endif

    /// Set a configuration ini file option, or clear it if no name passed
    Option *set_config(std::string option_name = "",
                       std::string default_filename = "",
                       const std::string &help_message = "Read an ini file",
                       bool config_required = false) {

        // Remove existing config if present
        if(config_ptr_ != nullptr) {
            remove_option(config_ptr_);
            config_ptr_ = nullptr;  // need to remove the config_ptr completely
        }

        // Only add config if option passed
        if(!option_name.empty()) {
            config_ptr_ = add_option(option_name, help_message);
            if(config_required) {
                config_ptr_->required();
            }
            if(!default_filename.empty()) {
                config_ptr_->default_str(std::move(default_filename));
            }
            config_ptr_->configurable(false);
        }

        return config_ptr_;
    }

    /// Removes an option from the App. Takes an option pointer. Returns true if found and removed.
    bool remove_option(Option *opt) {
        // Make sure no links exist
        for(Option_p &op : options_) {
            op->remove_needs(opt);
            op->remove_excludes(opt);
        }

        if(help_ptr_ == opt)
            help_ptr_ = nullptr;
        if(help_all_ptr_ == opt)
            help_all_ptr_ = nullptr;

        auto iterator =
            std::find_if(std::begin(options_), std::end(options_), [opt](const Option_p &v) { return v.get() == opt; });
        if(iterator != std::end(options_)) {
            options_.erase(iterator);
            return true;
        }
        return false;
    }

    /// creates an option group as part of the given app
    template <typename T = Option_group>
    T *add_option_group(std::string group_name, std::string group_description = "") {
        auto option_group = std::make_shared<T>(std::move(group_description), group_name, this);
        auto ptr = option_group.get();
        // move to App_p for overload resolution on older gcc versions
        App_p app_ptr = std::dynamic_pointer_cast<App>(option_group);
        add_subcommand(std::move(app_ptr));
        return ptr;
    }

    ///@}
    /// @name Subcommands
    ///@{

    /// Add a subcommand. Inherits INHERITABLE and OptionDefaults, and help flag
    App *add_subcommand(std::string subcommand_name = "", std::string subcommand_description = "") {
        if(!subcommand_name.empty() && !detail::valid_name_string(subcommand_name)) {
            if(!detail::valid_first_char(subcommand_name[0])) {
                throw IncorrectConstruction(
                    "Subcommand name starts with invalid character, allowed characters are [a-zA-z0-9]+'_','?','@' ");
            }
            for(auto c : subcommand_name) {
                if(!detail::valid_later_char(c)) {
                    throw IncorrectConstruction(std::string("Subcommand name contains invalid character ('") + c +
                                                "'), allowed characters are "
                                                "[a-zA-z0-9]+'_','?','@','.','-' ");
                }
            }
        }
        CLI::App_p subcom = std::shared_ptr<App>(new App(std::move(subcommand_description), subcommand_name, this));
        return add_subcommand(std::move(subcom));
    }

    /// Add a previously created app as a subcommand
    App *add_subcommand(CLI::App_p subcom) {
        if(!subcom)
            throw IncorrectConstruction("passed App is not valid");
        auto ckapp = (name_.empty() && parent_ != nullptr) ? _get_fallthrough_parent() : this;
        auto &mstrg = _compare_subcommand_names(*subcom, *ckapp);
        if(!mstrg.empty()) {
            throw(OptionAlreadyAdded("subcommand name or alias matches existing subcommand: " + mstrg));
        }
        subcom->parent_ = this;
        subcommands_.push_back(std::move(subcom));
        return subcommands_.back().get();
    }

    /// Removes a subcommand from the App. Takes a subcommand pointer. Returns true if found and removed.
    bool remove_subcommand(App *subcom) {
        // Make sure no links exist
        for(App_p &sub : subcommands_) {
            sub->remove_excludes(subcom);
            sub->remove_needs(subcom);
        }

        auto iterator = std::find_if(
            std::begin(subcommands_), std::end(subcommands_), [subcom](const App_p &v) { return v.get() == subcom; });
        if(iterator != std::end(subcommands_)) {
            subcommands_.erase(iterator);
            return true;
        }
        return false;
    }
    /// Check to see if a subcommand is part of this command (doesn't have to be in command line)
    /// returns the first subcommand if passed a nullptr
    App *get_subcommand(const App *subcom) const {
        if(subcom == nullptr)
            throw OptionNotFound("nullptr passed");
        for(const App_p &subcomptr : subcommands_)
            if(subcomptr.get() == subcom)
                return subcomptr.get();
        throw OptionNotFound(subcom->get_name());
    }

    /// Check to see if a subcommand is part of this command (text version)
    App *get_subcommand(std::string subcom) const {
        auto subc = _find_subcommand(subcom, false, false);
        if(subc == nullptr)
            throw OptionNotFound(subcom);
        return subc;
    }
    /// Get a pointer to subcommand by index
    App *get_subcommand(int index = 0) const {
        if(index >= 0) {
            auto uindex = static_cast<unsigned>(index);
            if(uindex < subcommands_.size())
                return subcommands_[uindex].get();
        }
        throw OptionNotFound(std::to_string(index));
    }

    /// Check to see if a subcommand is part of this command and get a shared_ptr to it
    CLI::App_p get_subcommand_ptr(App *subcom) const {
        if(subcom == nullptr)
            throw OptionNotFound("nullptr passed");
        for(const App_p &subcomptr : subcommands_)
            if(subcomptr.get() == subcom)
                return subcomptr;
        throw OptionNotFound(subcom->get_name());
    }

    /// Check to see if a subcommand is part of this command (text version)
    CLI::App_p get_subcommand_ptr(std::string subcom) const {
        for(const App_p &subcomptr : subcommands_)
            if(subcomptr->check_name(subcom))
                return subcomptr;
        throw OptionNotFound(subcom);
    }

    /// Get an owning pointer to subcommand by index
    CLI::App_p get_subcommand_ptr(int index = 0) const {
        if(index >= 0) {
            auto uindex = static_cast<unsigned>(index);
            if(uindex < subcommands_.size())
                return subcommands_[uindex];
        }
        throw OptionNotFound(std::to_string(index));
    }

    /// Check to see if an option group is part of this App
    App *get_option_group(std::string group_name) const {
        for(const App_p &app : subcommands_) {
            if(app->name_.empty() && app->group_ == group_name) {
                return app.get();
            }
        }
        throw OptionNotFound(group_name);
    }

    /// No argument version of count counts the number of times this subcommand was
    /// passed in. The main app will return 1. Unnamed subcommands will also return 1 unless
    /// otherwise modified in a callback
    std::size_t count() const { return parsed_; }

    /// Get a count of all the arguments processed in options and subcommands, this excludes arguments which were
    /// treated as extras.
    std::size_t count_all() const {
        std::size_t cnt{0};
        for(auto &opt : options_) {
            cnt += opt->count();
        }
        for(auto &sub : subcommands_) {
            cnt += sub->count_all();
        }
        if(!get_name().empty()) {  // for named subcommands add the number of times the subcommand was called
            cnt += parsed_;
        }
        return cnt;
    }

    /// Changes the group membership
    App *group(std::string group_name) {
        group_ = group_name;
        return this;
    }

    /// The argumentless form of require subcommand requires 1 or more subcommands
    App *require_subcommand() {
        require_subcommand_min_ = 1;
        require_subcommand_max_ = 0;
        return this;
    }

    /// Require a subcommand to be given (does not affect help call)
    /// The number required can be given. Negative values indicate maximum
    /// number allowed (0 for any number). Max number inheritable.
    App *require_subcommand(int value) {
        if(value < 0) {
            require_subcommand_min_ = 0;
            require_subcommand_max_ = static_cast<std::size_t>(-value);
        } else {
            require_subcommand_min_ = static_cast<std::size_t>(value);
            require_subcommand_max_ = static_cast<std::size_t>(value);
        }
        return this;
    }

    /// Explicitly control the number of subcommands required. Setting 0
    /// for the max means unlimited number allowed. Max number inheritable.
    App *require_subcommand(std::size_t min, std::size_t max) {
        require_subcommand_min_ = min;
        require_subcommand_max_ = max;
        return this;
    }

    /// The argumentless form of require option requires 1 or more options be used
    App *require_option() {
        require_option_min_ = 1;
        require_option_max_ = 0;
        return this;
    }

    /// Require an option to be given (does not affect help call)
    /// The number required can be given. Negative values indicate maximum
    /// number allowed (0 for any number).
    App *require_option(int value) {
        if(value < 0) {
            require_option_min_ = 0;
            require_option_max_ = static_cast<std::size_t>(-value);
        } else {
            require_option_min_ = static_cast<std::size_t>(value);
            require_option_max_ = static_cast<std::size_t>(value);
        }
        return this;
    }

    /// Explicitly control the number of options required. Setting 0
    /// for the max means unlimited number allowed. Max number inheritable.
    App *require_option(std::size_t min, std::size_t max) {
        require_option_min_ = min;
        require_option_max_ = max;
        return this;
    }

    /// Stop subcommand fallthrough, so that parent commands cannot collect commands after subcommand.
    /// Default from parent, usually set on parent.
    App *fallthrough(bool value = true) {
        fallthrough_ = value;
        return this;
    }

    /// Check to see if this subcommand was parsed, true only if received on command line.
    /// This allows the subcommand to be directly checked.
    explicit operator bool() const { return parsed_ > 0; }

    ///@}
    /// @name Extras for subclassing
    ///@{

    /// This allows subclasses to inject code before callbacks but after parse.
    ///
    /// This does not run if any errors or help is thrown.
    virtual void pre_callback() {}

    ///@}
    /// @name Parsing
    ///@{
    //
    /// Reset the parsed data
    void clear() {

        parsed_ = 0;
        pre_parse_called_ = false;

        missing_.clear();
        parsed_subcommands_.clear();
        for(const Option_p &opt : options_) {
            opt->clear();
        }
        for(const App_p &subc : subcommands_) {
            subc->clear();
        }
    }

    /// Parses the command line - throws errors.
    /// This must be called after the options are in but before the rest of the program.
    void parse(int argc, const char *const *argv) {
        // If the name is not set, read from command line
        if(name_.empty() || has_automatic_name_) {
            has_automatic_name_ = true;
            name_ = argv[0];
        }

        std::vector<std::string> args;
        args.reserve(static_cast<std::size_t>(argc) - 1);
        for(int i = argc - 1; i > 0; i--)
            args.emplace_back(argv[i]);
        parse(std::move(args));
    }

    /// Parse a single string as if it contained command line arguments.
    /// This function splits the string into arguments then calls parse(std::vector<std::string> &)
    /// the function takes an optional boolean argument specifying if the programName is included in the string to
    /// process
    void parse(std::string commandline, bool program_name_included = false) {

        if(program_name_included) {
            auto nstr = detail::split_program_name(commandline);
            if((name_.empty()) || (has_automatic_name_)) {
                has_automatic_name_ = true;
                name_ = nstr.first;
            }
            commandline = std::move(nstr.second);
        } else {
            detail::trim(commandline);
        }
        // the next section of code is to deal with quoted arguments after an '=' or ':' for windows like operations
        if(!commandline.empty()) {
            commandline = detail::find_and_modify(commandline, "=", detail::escape_detect);
            if(allow_windows_style_options_)
                commandline = detail::find_and_modify(commandline, ":", detail::escape_detect);
        }

        auto args = detail::split_up(std::move(commandline));
        // remove all empty strings
        args.erase(std::remove(args.begin(), args.end(), std::string{}), args.end());
        std::reverse(args.begin(), args.end());

        parse(std::move(args));
    }

    /// The real work is done here. Expects a reversed vector.
    /// Changes the vector to the remaining options.
    void parse(std::vector<std::string> &args) {
        // Clear if parsed
        if(parsed_ > 0)
            clear();

        // parsed_ is incremented in commands/subcommands,
        // but placed here to make sure this is cleared when
        // running parse after an error is thrown, even by _validate or _configure.
        parsed_ = 1;
        _validate();
        _configure();
        // set the parent as nullptr as this object should be the top now
        parent_ = nullptr;
        parsed_ = 0;

        _parse(args);
        run_callback();
    }

    /// The real work is done here. Expects a reversed vector.
    void parse(std::vector<std::string> &&args) {
        // Clear if parsed
        if(parsed_ > 0)
            clear();

        // parsed_ is incremented in commands/subcommands,
        // but placed here to make sure this is cleared when
        // running parse after an error is thrown, even by _validate or _configure.
        parsed_ = 1;
        _validate();
        _configure();
        // set the parent as nullptr as this object should be the top now
        parent_ = nullptr;
        parsed_ = 0;

        _parse(std::move(args));
        run_callback();
    }

    /// Provide a function to print a help message. The function gets access to the App pointer and error.
    void failure_message(std::function<std::string(const App *, const Error &e)> function) {
        failure_message_ = function;
    }

    /// Print a nice error message and return the exit code
    int exit(const Error &e, std::ostream &out = std::cout, std::ostream &err = std::cerr) const {

        /// Avoid printing anything if this is a CLI::RuntimeError
        if(e.get_name() == "RuntimeError")
            return e.get_exit_code();

        if(e.get_name() == "CallForHelp") {
            out << help();
            return e.get_exit_code();
        }

        if(e.get_name() == "CallForAllHelp") {
            out << help("", AppFormatMode::All);
            return e.get_exit_code();
        }

        if(e.get_name() == "CallForVersion") {
            out << e.what() << std::endl;
            return e.get_exit_code();
        }

        if(e.get_exit_code() != static_cast<int>(ExitCodes::Success)) {
            if(failure_message_)
                err << failure_message_(this, e) << std::flush;
        }

        return e.get_exit_code();
    }

    ///@}
    /// @name Post parsing
    ///@{

    /// Counts the number of times the given option was passed.
    std::size_t count(std::string option_name) const { return get_option(option_name)->count(); }

    /// Get a subcommand pointer list to the currently selected subcommands (after parsing by default, in command
    /// line order; use parsed = false to get the original definition list.)
    std::vector<App *> get_subcommands() const { return parsed_subcommands_; }

    /// Get a filtered subcommand pointer list from the original definition list. An empty function will provide all
    /// subcommands (const)
    std::vector<const App *> get_subcommands(const std::function<bool(const App *)> &filter) const {
        std::vector<const App *> subcomms(subcommands_.size());
        std::transform(std::begin(subcommands_), std::end(subcommands_), std::begin(subcomms), [](const App_p &v) {
            return v.get();
        });

        if(filter) {
            subcomms.erase(std::remove_if(std::begin(subcomms),
                                          std::end(subcomms),
                                          [&filter](const App *app) { return !filter(app); }),
                           std::end(subcomms));
        }

        return subcomms;
    }

    /// Get a filtered subcommand pointer list from the original definition list. An empty function will provide all
    /// subcommands
    std::vector<App *> get_subcommands(const std::function<bool(App *)> &filter) {
        std::vector<App *> subcomms(subcommands_.size());
        std::transform(std::begin(subcommands_), std::end(subcommands_), std::begin(subcomms), [](const App_p &v) {
            return v.get();
        });

        if(filter) {
            subcomms.erase(
                std::remove_if(std::begin(subcomms), std::end(subcomms), [&filter](App *app) { return !filter(app); }),
                std::end(subcomms));
        }

        return subcomms;
    }

    /// Check to see if given subcommand was selected
    bool got_subcommand(const App *subcom) const {
        // get subcom needed to verify that this was a real subcommand
        return get_subcommand(subcom)->parsed_ > 0;
    }

    /// Check with name instead of pointer to see if subcommand was selected
    bool got_subcommand(std::string subcommand_name) const { return get_subcommand(subcommand_name)->parsed_ > 0; }

    /// Sets excluded options for the subcommand
    App *excludes(Option *opt) {
        if(opt == nullptr) {
            throw OptionNotFound("nullptr passed");
        }
        exclude_options_.insert(opt);
        return this;
    }

    /// Sets excluded subcommands for the subcommand
    App *excludes(App *app) {
        if(app == nullptr) {
            throw OptionNotFound("nullptr passed");
        }
        if(app == this) {
            throw OptionNotFound("cannot self reference in needs");
        }
        auto res = exclude_subcommands_.insert(app);
        // subcommand exclusion should be symmetric
        if(res.second) {
            app->exclude_subcommands_.insert(this);
        }
        return this;
    }

    App *needs(Option *opt) {
        if(opt == nullptr) {
            throw OptionNotFound("nullptr passed");
        }
        need_options_.insert(opt);
        return this;
    }

    App *needs(App *app) {
        if(app == nullptr) {
            throw OptionNotFound("nullptr passed");
        }
        if(app == this) {
            throw OptionNotFound("cannot self reference in needs");
        }
        need_subcommands_.insert(app);
        return this;
    }

    /// Removes an option from the excludes list of this subcommand
    bool remove_excludes(Option *opt) {
        auto iterator = std::find(std::begin(exclude_options_), std::end(exclude_options_), opt);
        if(iterator == std::end(exclude_options_)) {
            return false;
        }
        exclude_options_.erase(iterator);
        return true;
    }

    /// Removes a subcommand from the excludes list of this subcommand
    bool remove_excludes(App *app) {
        auto iterator = std::find(std::begin(exclude_subcommands_), std::end(exclude_subcommands_), app);
        if(iterator == std::end(exclude_subcommands_)) {
            return false;
        }
        auto other_app = *iterator;
        exclude_subcommands_.erase(iterator);
        other_app->remove_excludes(this);
        return true;
    }

    /// Removes an option from the needs list of this subcommand
    bool remove_needs(Option *opt) {
        auto iterator = std::find(std::begin(need_options_), std::end(need_options_), opt);
        if(iterator == std::end(need_options_)) {
            return false;
        }
        need_options_.erase(iterator);
        return true;
    }

    /// Removes a subcommand from the needs list of this subcommand
    bool remove_needs(App *app) {
        auto iterator = std::find(std::begin(need_subcommands_), std::end(need_subcommands_), app);
        if(iterator == std::end(need_subcommands_)) {
            return false;
        }
        need_subcommands_.erase(iterator);
        return true;
    }

    ///@}
    /// @name Help
    ///@{

    /// Set footer.
    App *footer(std::string footer_string) {
        footer_ = std::move(footer_string);
        return this;
    }
    /// Set footer.
    App *footer(std::function<std::string()> footer_function) {
        footer_callback_ = std::move(footer_function);
        return this;
    }
    /// Produce a string that could be read in as a config of the current values of the App. Set default_also to
    /// include default arguments. write_descriptions will print a description for the App and for each option.
    std::string config_to_str(bool default_also = false, bool write_description = false) const {
        return config_formatter_->to_config(this, default_also, write_description, "");
    }

    /// Makes a help message, using the currently configured formatter
    /// Will only do one subcommand at a time
    std::string help(std::string prev = "", AppFormatMode mode = AppFormatMode::Normal) const {
        if(prev.empty())
            prev = get_name();
        else
            prev += " " + get_name();

        // Delegate to subcommand if needed
        auto selected_subcommands = get_subcommands();
        if(!selected_subcommands.empty()) {
            return selected_subcommands.at(0)->help(prev, mode);
        }
        return formatter_->make_help(this, prev, mode);
    }

    /// Displays a version string
    std::string version() const {
        std::string val;
        if(version_ptr_ != nullptr) {
            auto rv = version_ptr_->results();
            version_ptr_->clear();
            version_ptr_->add_result("true");
            try {
                version_ptr_->run_callback();
            } catch(const CLI::CallForVersion &cfv) {
                val = cfv.what();
            }
            version_ptr_->clear();
            version_ptr_->add_result(rv);
        }
        return val;
    }
    ///@}
    /// @name Getters
    ///@{

    /// Access the formatter
    std::shared_ptr<FormatterBase> get_formatter() const { return formatter_; }

    /// Access the config formatter
    std::shared_ptr<Config> get_config_formatter() const { return config_formatter_; }

    /// Access the config formatter as a configBase pointer
    std::shared_ptr<ConfigBase> get_config_formatter_base() const {
        // This is safer as a dynamic_cast if we have RTTI, as Config -> ConfigBase
#if defined(__cpp_rtti) || (defined(__GXX_RTTI) && __GXX_RTTI) || (defined(_HAS_STATIC_RTTI) && (_HAS_STATIC_RTTI == 0))
        return std::dynamic_pointer_cast<ConfigBase>(config_formatter_);
#else
        return std::static_pointer_cast<ConfigBase>(config_formatter_);
#endif
    }

    /// Get the app or subcommand description
    std::string get_description() const { return description_; }

    /// Set the description of the app
    App *description(std::string app_description) {
        description_ = std::move(app_description);
        return this;
    }

    /// Get the list of options (user facing function, so returns raw pointers), has optional filter function
    std::vector<const Option *> get_options(const std::function<bool(const Option *)> filter = {}) const {
        std::vector<const Option *> options(options_.size());
        std::transform(std::begin(options_), std::end(options_), std::begin(options), [](const Option_p &val) {
            return val.get();
        });

        if(filter) {
            options.erase(std::remove_if(std::begin(options),
                                         std::end(options),
                                         [&filter](const Option *opt) { return !filter(opt); }),
                          std::end(options));
        }

        return options;
    }

    /// Non-const version of the above
    std::vector<Option *> get_options(const std::function<bool(Option *)> filter = {}) {
        std::vector<Option *> options(options_.size());
        std::transform(std::begin(options_), std::end(options_), std::begin(options), [](const Option_p &val) {
            return val.get();
        });

        if(filter) {
            options.erase(
                std::remove_if(std::begin(options), std::end(options), [&filter](Option *opt) { return !filter(opt); }),
                std::end(options));
        }

        return options;
    }

    /// Get an option by name (noexcept non-const version)
    Option *get_option_no_throw(std::string option_name) noexcept {
        for(Option_p &opt : options_) {
            if(opt->check_name(option_name)) {
                return opt.get();
            }
        }
        for(auto &subc : subcommands_) {
            // also check down into nameless subcommands
            if(subc->get_name().empty()) {
                auto opt = subc->get_option_no_throw(option_name);
                if(opt != nullptr) {
                    return opt;
                }
            }
        }
        return nullptr;
    }

    /// Get an option by name (noexcept const version)
    const Option *get_option_no_throw(std::string option_name) const noexcept {
        for(const Option_p &opt : options_) {
            if(opt->check_name(option_name)) {
                return opt.get();
            }
        }
        for(const auto &subc : subcommands_) {
            // also check down into nameless subcommands
            if(subc->get_name().empty()) {
                auto opt = subc->get_option_no_throw(option_name);
                if(opt != nullptr) {
                    return opt;
                }
            }
        }
        return nullptr;
    }

    /// Get an option by name
    const Option *get_option(std::string option_name) const {
        auto opt = get_option_no_throw(option_name);
        if(opt == nullptr) {
            throw OptionNotFound(option_name);
        }
        return opt;
    }

    /// Get an option by name (non-const version)
    Option *get_option(std::string option_name) {
        auto opt = get_option_no_throw(option_name);
        if(opt == nullptr) {
            throw OptionNotFound(option_name);
        }
        return opt;
    }

    /// Shortcut bracket operator for getting a pointer to an option
    const Option *operator[](const std::string &option_name) const { return get_option(option_name); }

    /// Shortcut bracket operator for getting a pointer to an option
    const Option *operator[](const char *option_name) const { return get_option(option_name); }

    /// Check the status of ignore_case
    bool get_ignore_case() const { return ignore_case_; }

    /// Check the status of ignore_underscore
    bool get_ignore_underscore() const { return ignore_underscore_; }

    /// Check the status of fallthrough
    bool get_fallthrough() const { return fallthrough_; }

    /// Check the status of the allow windows style options
    bool get_allow_windows_style_options() const { return allow_windows_style_options_; }

    /// Check the status of the allow windows style options
    bool get_positionals_at_end() const { return positionals_at_end_; }

    /// Check the status of the allow windows style options
    bool get_configurable() const { return configurable_; }

    /// Get the group of this subcommand
    const std::string &get_group() const { return group_; }

    /// Generate and return the footer.
    std::string get_footer() const { return (footer_callback_) ? footer_callback_() + '\n' + footer_ : footer_; }

    /// Get the required min subcommand value
    std::size_t get_require_subcommand_min() const { return require_subcommand_min_; }

    /// Get the required max subcommand value
    std::size_t get_require_subcommand_max() const { return require_subcommand_max_; }

    /// Get the required min option value
    std::size_t get_require_option_min() const { return require_option_min_; }

    /// Get the required max option value
    std::size_t get_require_option_max() const { return require_option_max_; }

    /// Get the prefix command status
    bool get_prefix_command() const { return prefix_command_; }

    /// Get the status of allow extras
    bool get_allow_extras() const { return allow_extras_; }

    /// Get the status of required
    bool get_required() const { return required_; }

    /// Get the status of disabled
    bool get_disabled() const { return disabled_; }

    /// Get the status of silence
    bool get_silent() const { return silent_; }

    /// Get the status of disabled
    bool get_immediate_callback() const { return immediate_callback_; }

    /// Get the status of disabled by default
    bool get_disabled_by_default() const { return (default_startup == startup_mode::disabled); }

    /// Get the status of disabled by default
    bool get_enabled_by_default() const { return (default_startup == startup_mode::enabled); }
    /// Get the status of validating positionals
    bool get_validate_positionals() const { return validate_positionals_; }

    /// Get the status of allow extras
    config_extras_mode get_allow_config_extras() const { return allow_config_extras_; }

    /// Get a pointer to the help flag.
    Option *get_help_ptr() { return help_ptr_; }

    /// Get a pointer to the help flag. (const)
    const Option *get_help_ptr() const { return help_ptr_; }

    /// Get a pointer to the help all flag. (const)
    const Option *get_help_all_ptr() const { return help_all_ptr_; }

    /// Get a pointer to the config option.
    Option *get_config_ptr() { return config_ptr_; }

    /// Get a pointer to the config option. (const)
    const Option *get_config_ptr() const { return config_ptr_; }

    /// Get a pointer to the version option.
    Option *get_version_ptr() { return version_ptr_; }

    /// Get a pointer to the version option. (const)
    const Option *get_version_ptr() const { return version_ptr_; }

    /// Get the parent of this subcommand (or nullptr if master app)
    App *get_parent() { return parent_; }

    /// Get the parent of this subcommand (or nullptr if master app) (const version)
    const App *get_parent() const { return parent_; }

    /// Get the name of the current app
    const std::string &get_name() const { return name_; }

    /// Get the aliases of the current app
    const std::vector<std::string> &get_aliases() const { return aliases_; }

    /// clear all the aliases of the current App
    App *clear_aliases() {
        aliases_.clear();
        return this;
    }

    /// Get a display name for an app
    std::string get_display_name(bool with_aliases = false) const {
        if(name_.empty()) {
            return std::string("[Option Group: ") + get_group() + "]";
        }
        if(aliases_.empty() || !with_aliases || aliases_.empty()) {
            return name_;
        }
        std::string dispname = name_;
        for(const auto &lalias : aliases_) {
            dispname.push_back(',');
            dispname.push_back(' ');
            dispname.append(lalias);
        }
        return dispname;
    }

    /// Check the name, case insensitive and underscore insensitive if set
    bool check_name(std::string name_to_check) const {
        std::string local_name = name_;
        if(ignore_underscore_) {
            local_name = detail::remove_underscore(name_);
            name_to_check = detail::remove_underscore(name_to_check);
        }
        if(ignore_case_) {
            local_name = detail::to_lower(name_);
            name_to_check = detail::to_lower(name_to_check);
        }

        if(local_name == name_to_check) {
            return true;
        }
        for(auto les : aliases_) {
            if(ignore_underscore_) {
                les = detail::remove_underscore(les);
            }
            if(ignore_case_) {
                les = detail::to_lower(les);
            }
            if(les == name_to_check) {
                return true;
            }
        }
        return false;
    }

    /// Get the groups available directly from this option (in order)
    std::vector<std::string> get_groups() const {
        std::vector<std::string> groups;

        for(const Option_p &opt : options_) {
            // Add group if it is not already in there
            if(std::find(groups.begin(), groups.end(), opt->get_group()) == groups.end()) {
                groups.push_back(opt->get_group());
            }
        }

        return groups;
    }

    /// This gets a vector of pointers with the original parse order
    const std::vector<Option *> &parse_order() const { return parse_order_; }

    /// This returns the missing options from the current subcommand
    std::vector<std::string> remaining(bool recurse = false) const {
        std::vector<std::string> miss_list;
        for(const std::pair<detail::Classifier, std::string> &miss : missing_) {
            miss_list.push_back(std::get<1>(miss));
        }
        // Get from a subcommand that may allow extras
        if(recurse) {
            if(!allow_extras_) {
                for(const auto &sub : subcommands_) {
                    if(sub->name_.empty() && !sub->missing_.empty()) {
                        for(const std::pair<detail::Classifier, std::string> &miss : sub->missing_) {
                            miss_list.push_back(std::get<1>(miss));
                        }
                    }
                }
            }
            // Recurse into subcommands

            for(const App *sub : parsed_subcommands_) {
                std::vector<std::string> output = sub->remaining(recurse);
                std::copy(std::begin(output), std::end(output), std::back_inserter(miss_list));
            }
        }
        return miss_list;
    }

    /// This returns the missing options in a form ready for processing by another command line program
    std::vector<std::string> remaining_for_passthrough(bool recurse = false) const {
        std::vector<std::string> miss_list = remaining(recurse);
        std::reverse(std::begin(miss_list), std::end(miss_list));
        return miss_list;
    }

    /// This returns the number of remaining options, minus the -- separator
    std::size_t remaining_size(bool recurse = false) const {
        auto remaining_options = static_cast<std::size_t>(std::count_if(
            std::begin(missing_), std::end(missing_), [](const std::pair<detail::Classifier, std::string> &val) {
                return val.first != detail::Classifier::POSITIONAL_MARK;
            }));

        if(recurse) {
            for(const App_p &sub : subcommands_) {
                remaining_options += sub->remaining_size(recurse);
            }
        }
        return remaining_options;
    }

    ///@}

  protected:
    /// Check the options to make sure there are no conflicts.
    ///
    /// Currently checks to see if multiple positionals exist with unlimited args and checks if the min and max options
    /// are feasible
    void _validate() const {
        // count the number of positional only args
        auto pcount = std::count_if(std::begin(options_), std::end(options_), [](const Option_p &opt) {
            return opt->get_items_expected_max() >= detail::expected_max_vector_size && !opt->nonpositional();
        });
        if(pcount > 1) {
            auto pcount_req = std::count_if(std::begin(options_), std::end(options_), [](const Option_p &opt) {
                return opt->get_items_expected_max() >= detail::expected_max_vector_size && !opt->nonpositional() &&
                       opt->get_required();
            });
            if(pcount - pcount_req > 1) {
                throw InvalidError(name_);
            }
        }

        std::size_t nameless_subs{0};
        for(const App_p &app : subcommands_) {
            app->_validate();
            if(app->get_name().empty())
                ++nameless_subs;
        }

        if(require_option_min_ > 0) {
            if(require_option_max_ > 0) {
                if(require_option_max_ < require_option_min_) {
                    throw(InvalidError("Required min options greater than required max options",
                                       ExitCodes::InvalidError));
                }
            }
            if(require_option_min_ > (options_.size() + nameless_subs)) {
                throw(InvalidError("Required min options greater than number of available options",
                                   ExitCodes::InvalidError));
            }
        }
    }

    /// configure subcommands to enable parsing through the current object
    /// set the correct fallthrough and prefix for nameless subcommands and manage the automatic enable or disable
    /// makes sure parent is set correctly
    void _configure() {
        if(default_startup == startup_mode::enabled) {
            disabled_ = false;
        } else if(default_startup == startup_mode::disabled) {
            disabled_ = true;
        }
        for(const App_p &app : subcommands_) {
            if(app->has_automatic_name_) {
                app->name_.clear();
            }
            if(app->name_.empty()) {
                app->fallthrough_ = false;  // make sure fallthrough_ is false to prevent infinite loop
                app->prefix_command_ = false;
            }
            // make sure the parent is set to be this object in preparation for parse
            app->parent_ = this;
            app->_configure();
        }
    }

    /// Internal function to run (App) callback, bottom up
    void run_callback(bool final_mode = false, bool suppress_final_callback = false) {
        pre_callback();
        // in the main app if immediate_callback_ is set it runs the main callback before the used subcommands
        if(!final_mode && parse_complete_callback_) {
            parse_complete_callback_();
        }
        // run the callbacks for the received subcommands
        for(App *subc : get_subcommands()) {
            subc->run_callback(true, suppress_final_callback);
        }
        // now run callbacks for option_groups
        for(auto &subc : subcommands_) {
            if(subc->name_.empty() && subc->count_all() > 0) {
                subc->run_callback(true, suppress_final_callback);
            }
        }

        // finally run the main callback
        if(final_callback_ && (parsed_ > 0) && (!suppress_final_callback)) {
            if(!name_.empty() || count_all() > 0 || parent_ == nullptr) {
                final_callback_();
            }
        }
    }

    /// Check to see if a subcommand is valid. Give up immediately if subcommand max has been reached.
    bool _valid_subcommand(const std::string &current, bool ignore_used = true) const {
        // Don't match if max has been reached - but still check parents
        if(require_subcommand_max_ != 0 && parsed_subcommands_.size() >= require_subcommand_max_) {
            return parent_ != nullptr && parent_->_valid_subcommand(current, ignore_used);
        }
        auto com = _find_subcommand(current, true, ignore_used);
        if(com != nullptr) {
            return true;
        }
        // Check parent if exists, else return false
        return parent_ != nullptr && parent_->_valid_subcommand(current, ignore_used);
    }

    /// Selects a Classifier enum based on the type of the current argument
    detail::Classifier _recognize(const std::string &current, bool ignore_used_subcommands = true) const {
        std::string dummy1, dummy2;

        if(current == "--")
            return detail::Classifier::POSITIONAL_MARK;
        if(_valid_subcommand(current, ignore_used_subcommands))
            return detail::Classifier::SUBCOMMAND;
        if(detail::split_long(current, dummy1, dummy2))
            return detail::Classifier::LONG;
        if(detail::split_short(current, dummy1, dummy2)) {
            if(dummy1[0] >= '0' && dummy1[0] <= '9') {
                if(get_option_no_throw(std::string{'-', dummy1[0]}) == nullptr) {
                    return detail::Classifier::NONE;
                }
            }
            return detail::Classifier::SHORT;
        }
        if((allow_windows_style_options_) && (detail::split_windows_style(current, dummy1, dummy2)))
            return detail::Classifier::WINDOWS_STYLE;
        if((current == "++") && !name_.empty() && parent_ != nullptr)
            return detail::Classifier::SUBCOMMAND_TERMINATOR;
        return detail::Classifier::NONE;
    }

    // The parse function is now broken into several parts, and part of process

    /// Read and process a configuration file (main app only)
    void _process_config_file() {
        if(config_ptr_ != nullptr) {
            bool config_required = config_ptr_->get_required();
            auto file_given = config_ptr_->count() > 0;
            auto config_files = config_ptr_->as<std::vector<std::string>>();
            if(config_files.empty() || config_files.front().empty()) {
                if(config_required) {
                    throw FileError::Missing("no specified config file");
                }
                return;
            }
            for(auto rit = config_files.rbegin(); rit != config_files.rend(); ++rit) {
                const auto &config_file = *rit;
                auto path_result = detail::check_path(config_file.c_str());
                if(path_result == detail::path_type::file) {
                    try {
                        std::vector<ConfigItem> values = config_formatter_->from_file(config_file);
                        _parse_config(values);
                        if(!file_given) {
                            config_ptr_->add_result(config_file);
                        }
                    } catch(const FileError &) {
                        if(config_required || file_given)
                            throw;
                    }
                } else if(config_required || file_given) {
                    throw FileError::Missing(config_file);
                }
            }
        }
    }

    /// Get envname options if not yet passed. Runs on *all* subcommands.
    void _process_env() {
        for(const Option_p &opt : options_) {
            if(opt->count() == 0 && !opt->envname_.empty()) {
                char *buffer = nullptr;
                std::string ename_string;

#ifdef _MSC_VER
                // Windows version
                std::size_t sz = 0;
                if(_dupenv_s(&buffer, &sz, opt->envname_.c_str()) == 0 && buffer != nullptr) {
                    ename_string = std::string(buffer);
                    free(buffer);
                }
#else
                // This also works on Windows, but gives a warning
                buffer = std::getenv(opt->envname_.c_str());
                if(buffer != nullptr)
                    ename_string = std::string(buffer);
#endif

                if(!ename_string.empty()) {
                    opt->add_result(ename_string);
                }
            }
        }

        for(App_p &sub : subcommands_) {
            if(sub->get_name().empty() || !sub->parse_complete_callback_)
                sub->_process_env();
        }
    }

    /// Process callbacks. Runs on *all* subcommands.
    void _process_callbacks() {

        for(App_p &sub : subcommands_) {
            // process the priority option_groups first
            if(sub->get_name().empty() && sub->parse_complete_callback_) {
                if(sub->count_all() > 0) {
                    sub->_process_callbacks();
                    sub->run_callback();
                }
            }
        }

        for(const Option_p &opt : options_) {
            if(opt->count() > 0 && !opt->get_callback_run()) {
                opt->run_callback();
            }
        }
        for(App_p &sub : subcommands_) {
            if(!sub->parse_complete_callback_) {
                sub->_process_callbacks();
            }
        }
    }

    /// Run help flag processing if any are found.
    ///
    /// The flags allow recursive calls to remember if there was a help flag on a parent.
    void _process_help_flags(bool trigger_help = false, bool trigger_all_help = false) const {
        const Option *help_ptr = get_help_ptr();
        const Option *help_all_ptr = get_help_all_ptr();

        if(help_ptr != nullptr && help_ptr->count() > 0)
            trigger_help = true;
        if(help_all_ptr != nullptr && help_all_ptr->count() > 0)
            trigger_all_help = true;

        // If there were parsed subcommands, call those. First subcommand wins if there are multiple ones.
        if(!parsed_subcommands_.empty()) {
            for(const App *sub : parsed_subcommands_)
                sub->_process_help_flags(trigger_help, trigger_all_help);

            // Only the final subcommand should call for help. All help wins over help.
        } else if(trigger_all_help) {
            throw CallForAllHelp();
        } else if(trigger_help) {
            throw CallForHelp();
        }
    }

    /// Verify required options and cross requirements. Subcommands too (only if selected).
    void _process_requirements() {
        // check excludes
        bool excluded{false};
        std::string excluder;
        for(auto &opt : exclude_options_) {
            if(opt->count() > 0) {
                excluded = true;
                excluder = opt->get_name();
            }
        }
        for(auto &subc : exclude_subcommands_) {
            if(subc->count_all() > 0) {
                excluded = true;
                excluder = subc->get_display_name();
            }
        }
        if(excluded) {
            if(count_all() > 0) {
                throw ExcludesError(get_display_name(), excluder);
            }
            // if we are excluded but didn't receive anything, just return
            return;
        }

        // check excludes
        bool missing_needed{false};
        std::string missing_need;
        for(auto &opt : need_options_) {
            if(opt->count() == 0) {
                missing_needed = true;
                missing_need = opt->get_name();
            }
        }
        for(auto &subc : need_subcommands_) {
            if(subc->count_all() == 0) {
                missing_needed = true;
                missing_need = subc->get_display_name();
            }
        }
        if(missing_needed) {
            if(count_all() > 0) {
                throw RequiresError(get_display_name(), missing_need);
            }
            // if we missing something but didn't have any options, just return
            return;
        }

        std::size_t used_options = 0;
        for(const Option_p &opt : options_) {

            if(opt->count() != 0) {
                ++used_options;
            }
            // Required but empty
            if(opt->get_required() && opt->count() == 0) {
                throw RequiredError(opt->get_name());
            }
            // Requires
            for(const Option *opt_req : opt->needs_)
                if(opt->count() > 0 && opt_req->count() == 0)
                    throw RequiresError(opt->get_name(), opt_req->get_name());
            // Excludes
            for(const Option *opt_ex : opt->excludes_)
                if(opt->count() > 0 && opt_ex->count() != 0)
                    throw ExcludesError(opt->get_name(), opt_ex->get_name());
        }
        // check for the required number of subcommands
        if(require_subcommand_min_ > 0) {
            auto selected_subcommands = get_subcommands();
            if(require_subcommand_min_ > selected_subcommands.size())
                throw RequiredError::Subcommand(require_subcommand_min_);
        }

        // Max error cannot occur, the extra subcommand will parse as an ExtrasError or a remaining item.

        // run this loop to check how many unnamed subcommands were actually used since they are considered options
        // from the perspective of an App
        for(App_p &sub : subcommands_) {
            if(sub->disabled_)
                continue;
            if(sub->name_.empty() && sub->count_all() > 0) {
                ++used_options;
            }
        }

        if(require_option_min_ > used_options || (require_option_max_ > 0 && require_option_max_ < used_options)) {
            auto option_list = detail::join(options_, [this](const Option_p &ptr) {
                if(ptr.get() == help_ptr_ || ptr.get() == help_all_ptr_) {
                    return std::string{};
                }
                return ptr->get_name(false, true);
            });

            auto subc_list = get_subcommands([](App *app) { return ((app->get_name().empty()) && (!app->disabled_)); });
            if(!subc_list.empty()) {
                option_list += "," + detail::join(subc_list, [](const App *app) { return app->get_display_name(); });
            }
            throw RequiredError::Option(require_option_min_, require_option_max_, used_options, option_list);
        }

        // now process the requirements for subcommands if needed
        for(App_p &sub : subcommands_) {
            if(sub->disabled_)
                continue;
            if(sub->name_.empty() && sub->required_ == false) {
                if(sub->count_all() == 0) {
                    if(require_option_min_ > 0 && require_option_min_ <= used_options) {
                        continue;
                        // if we have met the requirement and there is nothing in this option group skip checking
                        // requirements
                    }
                    if(require_option_max_ > 0 && used_options >= require_option_min_) {
                        continue;
                        // if we have met the requirement and there is nothing in this option group skip checking
                        // requirements
                    }
                }
            }
            if(sub->count() > 0 || sub->name_.empty()) {
                sub->_process_requirements();
            }

            if(sub->required_ && sub->count_all() == 0) {
                throw(CLI::RequiredError(sub->get_display_name()));
            }
        }
    }

    /// Process callbacks and such.
    void _process() {
        CLI::FileError fe("ne");
        bool caught_error{false};
        try {
            // the config file might generate a FileError but that should not be processed until later in the process
            // to allow for help, version and other errors to generate first.
            _process_config_file();
            // process env shouldn't throw but no reason to process it if config generated an error
            _process_env();
        } catch(const CLI::FileError &fe2) {
            fe = fe2;
            caught_error = true;
        }
        // callbacks and help_flags can generate exceptions which should take priority over the config file error if one
        // exists
        _process_callbacks();
        _process_help_flags();

        if(caught_error) {
            throw CLI::FileError(std::move(fe));
        }

        _process_requirements();
    }

    /// Throw an error if anything is left over and should not be.
    void _process_extras() {
        if(!(allow_extras_ || prefix_command_)) {
            std::size_t num_left_over = remaining_size();
            if(num_left_over > 0) {
                throw ExtrasError(name_, remaining(false));
            }
        }

        for(App_p &sub : subcommands_) {
            if(sub->count() > 0)
                sub->_process_extras();
        }
    }

    /// Throw an error if anything is left over and should not be.
    /// Modifies the args to fill in the missing items before throwing.
    void _process_extras(std::vector<std::string> &args) {
        if(!(allow_extras_ || prefix_command_)) {
            std::size_t num_left_over = remaining_size();
            if(num_left_over > 0) {
                args = remaining(false);
                throw ExtrasError(name_, args);
            }
        }

        for(App_p &sub : subcommands_) {
            if(sub->count() > 0)
                sub->_process_extras(args);
        }
    }

    /// Internal function to recursively increment the parsed counter on the current app as well unnamed subcommands
    void increment_parsed() {
        ++parsed_;
        for(App_p &sub : subcommands_) {
            if(sub->get_name().empty())
                sub->increment_parsed();
        }
    }
    /// Internal parse function
    void _parse(std::vector<std::string> &args) {
        increment_parsed();
        _trigger_pre_parse(args.size());
        bool positional_only = false;

        while(!args.empty()) {
            if(!_parse_single(args, positional_only)) {
                break;
            }
        }

        if(parent_ == nullptr) {
            _process();

            // Throw error if any items are left over (depending on settings)
            _process_extras(args);

            // Convert missing (pairs) to extras (string only) ready for processing in another app
            args = remaining_for_passthrough(false);
        } else if(parse_complete_callback_) {
            _process_env();
            _process_callbacks();
            _process_help_flags();
            _process_requirements();
            run_callback(false, true);
        }
    }

    /// Internal parse function
    void _parse(std::vector<std::string> &&args) {
        // this can only be called by the top level in which case parent == nullptr by definition
        // operation is simplified
        increment_parsed();
        _trigger_pre_parse(args.size());
        bool positional_only = false;

        while(!args.empty()) {
            _parse_single(args, positional_only);
        }
        _process();

        // Throw error if any items are left over (depending on settings)
        _process_extras();
    }

    /// Parse one config param, return false if not found in any subcommand, remove if it is
    ///
    /// If this has more than one dot.separated.name, go into the subcommand matching it
    /// Returns true if it managed to find the option, if false you'll need to remove the arg manually.
    void _parse_config(const std::vector<ConfigItem> &args) {
        for(const ConfigItem &item : args) {
            if(!_parse_single_config(item) && allow_config_extras_ == config_extras_mode::error)
                throw ConfigError::Extras(item.fullname());
        }
    }

    /// Fill in a single config option
    bool _parse_single_config(const ConfigItem &item, std::size_t level = 0) {
        if(level < item.parents.size()) {
            try {
                auto subcom = get_subcommand(item.parents.at(level));
                auto result = subcom->_parse_single_config(item, level + 1);

                return result;
            } catch(const OptionNotFound &) {
                return false;
            }
        }
        // check for section open
        if(item.name == "++") {
            if(configurable_) {
                increment_parsed();
                _trigger_pre_parse(2);
                if(parent_ != nullptr) {
                    parent_->parsed_subcommands_.push_back(this);
                }
            }
            return true;
        }
        // check for section close
        if(item.name == "--") {
            if(configurable_) {
                _process_callbacks();
                _process_requirements();
                run_callback();
            }
            return true;
        }
        Option *op = get_option_no_throw("--" + item.name);
        if(op == nullptr) {
            if(item.name.size() == 1) {
                op = get_option_no_throw("-" + item.name);
            }
        }
        if(op == nullptr) {
            op = get_option_no_throw(item.name);
        }
        if(op == nullptr) {
            // If the option was not present
            if(get_allow_config_extras() == config_extras_mode::capture)
                // Should we worry about classifying the extras properly?
                missing_.emplace_back(detail::Classifier::NONE, item.fullname());
            return false;
        }

        if(!op->get_configurable())
            throw ConfigError::NotConfigurable(item.fullname());

        if(op->empty()) {
            // Flag parsing
            if(op->get_expected_min() == 0) {
                auto res = config_formatter_->to_flag(item);
                res = op->get_flag_value(item.name, res);

                op->add_result(res);

            } else {
                op->add_result(item.inputs);
                op->run_callback();
            }
        }

        return true;
    }

    /// Parse "one" argument (some may eat more than one), delegate to parent if fails, add to missing if missing
    /// from master return false if the parse has failed and needs to return to parent
    bool _parse_single(std::vector<std::string> &args, bool &positional_only) {
        bool retval = true;
        detail::Classifier classifier = positional_only ? detail::Classifier::NONE : _recognize(args.back());
        switch(classifier) {
        case detail::Classifier::POSITIONAL_MARK:
            args.pop_back();
            positional_only = true;
            if((!_has_remaining_positionals()) && (parent_ != nullptr)) {
                retval = false;
            } else {
                _move_to_missing(classifier, "--");
            }
            break;
        case detail::Classifier::SUBCOMMAND_TERMINATOR:
            // treat this like a positional mark if in the parent app
            args.pop_back();
            retval = false;
            break;
        case detail::Classifier::SUBCOMMAND:
            retval = _parse_subcommand(args);
            break;
        case detail::Classifier::LONG:
        case detail::Classifier::SHORT:
        case detail::Classifier::WINDOWS_STYLE:
            // If already parsed a subcommand, don't accept options_
            _parse_arg(args, classifier);
            break;
        case detail::Classifier::NONE:
            // Probably a positional or something for a parent (sub)command
            retval = _parse_positional(args, false);
            if(retval && positionals_at_end_) {
                positional_only = true;
            }
            break;
            // LCOV_EXCL_START
        default:
            throw HorribleError("unrecognized classifier (you should not see this!)");
            // LCOV_EXCL_STOP
        }
        return retval;
    }

    /// Count the required remaining positional arguments
    std::size_t _count_remaining_positionals(bool required_only = false) const {
        std::size_t retval = 0;
        for(const Option_p &opt : options_) {
            if(opt->get_positional() && (!required_only || opt->get_required())) {
                if(opt->get_items_expected_min() > 0 &&
                   static_cast<int>(opt->count()) < opt->get_items_expected_min()) {
                    retval += static_cast<std::size_t>(opt->get_items_expected_min()) - opt->count();
                }
            }
        }
        return retval;
    }

    /// Count the required remaining positional arguments
    bool _has_remaining_positionals() const {
        for(const Option_p &opt : options_) {
            if(opt->get_positional() && ((static_cast<int>(opt->count()) < opt->get_items_expected_min()))) {
                return true;
            }
        }

        return false;
    }

    /// Parse a positional, go up the tree to check
    /// @param haltOnSubcommand if set to true the operation will not process subcommands merely return false
    /// Return true if the positional was used false otherwise
    bool _parse_positional(std::vector<std::string> &args, bool haltOnSubcommand) {

        const std::string &positional = args.back();

        if(positionals_at_end_) {
            // deal with the case of required arguments at the end which should take precedence over other arguments
            auto arg_rem = args.size();
            auto remreq = _count_remaining_positionals(true);
            if(arg_rem <= remreq) {
                for(const Option_p &opt : options_) {
                    if(opt->get_positional() && opt->required_) {
                        if(static_cast<int>(opt->count()) < opt->get_items_expected_min()) {
                            if(validate_positionals_) {
                                std::string pos = positional;
                                pos = opt->_validate(pos, 0);
                                if(!pos.empty()) {
                                    continue;
                                }
                            }
                            opt->add_result(positional);
                            parse_order_.push_back(opt.get());
                            args.pop_back();
                            return true;
                        }
                    }
                }
            }
        }
        for(const Option_p &opt : options_) {
            // Eat options, one by one, until done
            if(opt->get_positional() &&
               (static_cast<int>(opt->count()) < opt->get_items_expected_min() || opt->get_allow_extra_args())) {
                if(validate_positionals_) {
                    std::string pos = positional;
                    pos = opt->_validate(pos, 0);
                    if(!pos.empty()) {
                        continue;
                    }
                }
                opt->add_result(positional);
                parse_order_.push_back(opt.get());
                args.pop_back();
                return true;
            }
        }

        for(auto &subc : subcommands_) {
            if((subc->name_.empty()) && (!subc->disabled_)) {
                if(subc->_parse_positional(args, false)) {
                    if(!subc->pre_parse_called_) {
                        subc->_trigger_pre_parse(args.size());
                    }
                    return true;
                }
            }
        }
        // let the parent deal with it if possible
        if(parent_ != nullptr && fallthrough_)
            return _get_fallthrough_parent()->_parse_positional(args, static_cast<bool>(parse_complete_callback_));

        /// Try to find a local subcommand that is repeated
        auto com = _find_subcommand(args.back(), true, false);
        if(com != nullptr && (require_subcommand_max_ == 0 || require_subcommand_max_ > parsed_subcommands_.size())) {
            if(haltOnSubcommand) {
                return false;
            }
            args.pop_back();
            com->_parse(args);
            return true;
        }
        /// now try one last gasp at subcommands that have been executed before, go to root app and try to find a
        /// subcommand in a broader way, if one exists let the parent deal with it
        auto parent_app = (parent_ != nullptr) ? _get_fallthrough_parent() : this;
        com = parent_app->_find_subcommand(args.back(), true, false);
        if(com != nullptr && (com->parent_->require_subcommand_max_ == 0 ||
                              com->parent_->require_subcommand_max_ > com->parent_->parsed_subcommands_.size())) {
            return false;
        }

        if(positionals_at_end_) {
            throw CLI::ExtrasError(name_, args);
        }
        /// If this is an option group don't deal with it
        if(parent_ != nullptr && name_.empty()) {
            return false;
        }
        /// We are out of other options this goes to missing
        _move_to_missing(detail::Classifier::NONE, positional);
        args.pop_back();
        if(prefix_command_) {
            while(!args.empty()) {
                _move_to_missing(detail::Classifier::NONE, args.back());
                args.pop_back();
            }
        }

        return true;
    }

    /// Locate a subcommand by name with two conditions, should disabled subcommands be ignored, and should used
    /// subcommands be ignored
    App *_find_subcommand(const std::string &subc_name, bool ignore_disabled, bool ignore_used) const noexcept {
        for(const App_p &com : subcommands_) {
            if(com->disabled_ && ignore_disabled)
                continue;
            if(com->get_name().empty()) {
                auto subc = com->_find_subcommand(subc_name, ignore_disabled, ignore_used);
                if(subc != nullptr) {
                    return subc;
                }
            }
            if(com->check_name(subc_name)) {
                if((!*com) || !ignore_used)
                    return com.get();
            }
        }
        return nullptr;
    }

    /// Parse a subcommand, modify args and continue
    ///
    /// Unlike the others, this one will always allow fallthrough
    /// return true if the subcommand was processed false otherwise
    bool _parse_subcommand(std::vector<std::string> &args) {
        if(_count_remaining_positionals(/* required */ true) > 0) {
            _parse_positional(args, false);
            return true;
        }
        auto com = _find_subcommand(args.back(), true, true);
        if(com != nullptr) {
            args.pop_back();
            if(!com->silent_) {
                parsed_subcommands_.push_back(com);
            }
            com->_parse(args);
            auto parent_app = com->parent_;
            while(parent_app != this) {
                parent_app->_trigger_pre_parse(args.size());
                if(!com->silent_) {
                    parent_app->parsed_subcommands_.push_back(com);
                }
                parent_app = parent_app->parent_;
            }
            return true;
        }

        if(parent_ == nullptr)
            throw HorribleError("Subcommand " + args.back() + " missing");
        return false;
    }

    /// Parse a short (false) or long (true) argument, must be at the top of the list
    /// return true if the argument was processed or false if nothing was done
    bool _parse_arg(std::vector<std::string> &args, detail::Classifier current_type) {

        std::string current = args.back();

        std::string arg_name;
        std::string value;
        std::string rest;

        switch(current_type) {
        case detail::Classifier::LONG:
            if(!detail::split_long(current, arg_name, value))
                throw HorribleError("Long parsed but missing (you should not see this):" + args.back());
            break;
        case detail::Classifier::SHORT:
            if(!detail::split_short(current, arg_name, rest))
                throw HorribleError("Short parsed but missing! You should not see this");
            break;
        case detail::Classifier::WINDOWS_STYLE:
            if(!detail::split_windows_style(current, arg_name, value))
                throw HorribleError("windows option parsed but missing! You should not see this");
            break;
        case detail::Classifier::SUBCOMMAND:
        case detail::Classifier::SUBCOMMAND_TERMINATOR:
        case detail::Classifier::POSITIONAL_MARK:
        case detail::Classifier::NONE:
        default:
            throw HorribleError("parsing got called with invalid option! You should not see this");
        }

        auto op_ptr =
            std::find_if(std::begin(options_), std::end(options_), [arg_name, current_type](const Option_p &opt) {
                if(current_type == detail::Classifier::LONG)
                    return opt->check_lname(arg_name);
                if(current_type == detail::Classifier::SHORT)
                    return opt->check_sname(arg_name);
                // this will only get called for detail::Classifier::WINDOWS_STYLE
                return opt->check_lname(arg_name) || opt->check_sname(arg_name);
            });

        // Option not found
        if(op_ptr == std::end(options_)) {
            for(auto &subc : subcommands_) {
                if(subc->name_.empty() && !subc->disabled_) {
                    if(subc->_parse_arg(args, current_type)) {
                        if(!subc->pre_parse_called_) {
                            subc->_trigger_pre_parse(args.size());
                        }
                        return true;
                    }
                }
            }
            // If a subcommand, try the master command
            if(parent_ != nullptr && fallthrough_)
                return _get_fallthrough_parent()->_parse_arg(args, current_type);
            // don't capture missing if this is a nameless subcommand
            if(parent_ != nullptr && name_.empty()) {
                return false;
            }
            // Otherwise, add to missing
            args.pop_back();
            _move_to_missing(current_type, current);
            return true;
        }

        args.pop_back();

        // Get a reference to the pointer to make syntax bearable
        Option_p &op = *op_ptr;
        /// if we require a separator add it here
        if(op->get_inject_separator()) {
            if(!op->results().empty() && !op->results().back().empty()) {
                op->add_result(std::string{});
            }
        }
        int min_num = (std::min)(op->get_type_size_min(), op->get_items_expected_min());
        int max_num = op->get_items_expected_max();
        // check container like options to limit the argument size to a single type if the allow_extra_flags argument is
        // set. 16 is somewhat arbitrary (needs to be at least 4)
        if(max_num >= detail::expected_max_vector_size / 16 && !op->get_allow_extra_args()) {
            auto tmax = op->get_type_size_max();
            max_num = detail::checked_multiply(tmax, op->get_expected_min()) ? tmax : detail::expected_max_vector_size;
        }
        // Make sure we always eat the minimum for unlimited vectors
        int collected = 0;     // total number of arguments collected
        int result_count = 0;  // local variable for number of results in a single arg string
        // deal with purely flag like things
        if(max_num == 0) {
            auto res = op->get_flag_value(arg_name, value);
            op->add_result(res);
            parse_order_.push_back(op.get());
        } else if(!value.empty()) {  // --this=value
            op->add_result(value, result_count);
            parse_order_.push_back(op.get());
            collected += result_count;
            // -Trest
        } else if(!rest.empty()) {
            op->add_result(rest, result_count);
            parse_order_.push_back(op.get());
            rest = "";
            collected += result_count;
        }

        // gather the minimum number of arguments
        while(min_num > collected && !args.empty()) {
            std::string current_ = args.back();
            args.pop_back();
            op->add_result(current_, result_count);
            parse_order_.push_back(op.get());
            collected += result_count;
        }

        if(min_num > collected) {  // if we have run out of arguments and the minimum was not met
            throw ArgumentMismatch::TypedAtLeast(op->get_name(), min_num, op->get_type_name());
        }

        if(max_num > collected || op->get_allow_extra_args()) {  // we allow optional arguments
            auto remreqpos = _count_remaining_positionals(true);
            // we have met the minimum now optionally check up to the maximum
            while((collected < max_num || op->get_allow_extra_args()) && !args.empty() &&
                  _recognize(args.back(), false) == detail::Classifier::NONE) {
                // If any required positionals remain, don't keep eating
                if(remreqpos >= args.size()) {
                    break;
                }

                op->add_result(args.back(), result_count);
                parse_order_.push_back(op.get());
                args.pop_back();
                collected += result_count;
            }

            // Allow -- to end an unlimited list and "eat" it
            if(!args.empty() && _recognize(args.back()) == detail::Classifier::POSITIONAL_MARK)
                args.pop_back();
            // optional flag that didn't receive anything now get the default value
            if(min_num == 0 && max_num > 0 && collected == 0) {
                auto res = op->get_flag_value(arg_name, std::string{});
                op->add_result(res);
                parse_order_.push_back(op.get());
            }
        }

        // if we only partially completed a type then add an empty string for later processing
        if(min_num > 0 && op->get_type_size_max() != min_num && (collected % op->get_type_size_max()) != 0) {
            op->add_result(std::string{});
        }

        if(!rest.empty()) {
            rest = "-" + rest;
            args.push_back(rest);
        }
        return true;
    }

    /// Trigger the pre_parse callback if needed
    void _trigger_pre_parse(std::size_t remaining_args) {
        if(!pre_parse_called_) {
            pre_parse_called_ = true;
            if(pre_parse_callback_) {
                pre_parse_callback_(remaining_args);
            }
        } else if(immediate_callback_) {
            if(!name_.empty()) {
                auto pcnt = parsed_;
                auto extras = std::move(missing_);
                clear();
                parsed_ = pcnt;
                pre_parse_called_ = true;
                missing_ = std::move(extras);
            }
        }
    }

    /// Get the appropriate parent to fallthrough to which is the first one that has a name or the main app
    App *_get_fallthrough_parent() {
        if(parent_ == nullptr) {
            throw(HorribleError("No Valid parent"));
        }
        auto fallthrough_parent = parent_;
        while((fallthrough_parent->parent_ != nullptr) && (fallthrough_parent->get_name().empty())) {
            fallthrough_parent = fallthrough_parent->parent_;
        }
        return fallthrough_parent;
    }

    /// Helper function to run through all possible comparisons of subcommand names to check there is no overlap
    const std::string &_compare_subcommand_names(const App &subcom, const App &base) const {
        static const std::string estring;
        if(subcom.disabled_) {
            return estring;
        }
        for(auto &subc : base.subcommands_) {
            if(subc.get() != &subcom) {
                if(subc->disabled_) {
                    continue;
                }
                if(!subcom.get_name().empty()) {
                    if(subc->check_name(subcom.get_name())) {
                        return subcom.get_name();
                    }
                }
                if(!subc->get_name().empty()) {
                    if(subcom.check_name(subc->get_name())) {
                        return subc->get_name();
                    }
                }
                for(const auto &les : subcom.aliases_) {
                    if(subc->check_name(les)) {
                        return les;
                    }
                }
                // this loop is needed in case of ignore_underscore or ignore_case on one but not the other
                for(const auto &les : subc->aliases_) {
                    if(subcom.check_name(les)) {
                        return les;
                    }
                }
                // if the subcommand is an option group we need to check deeper
                if(subc->get_name().empty()) {
                    auto &cmpres = _compare_subcommand_names(subcom, *subc);
                    if(!cmpres.empty()) {
                        return cmpres;
                    }
                }
                // if the test subcommand is an option group we need to check deeper
                if(subcom.get_name().empty()) {
                    auto &cmpres = _compare_subcommand_names(*subc, subcom);
                    if(!cmpres.empty()) {
                        return cmpres;
                    }
                }
            }
        }
        return estring;
    }
    /// Helper function to place extra values in the most appropriate position
    void _move_to_missing(detail::Classifier val_type, const std::string &val) {
        if(allow_extras_ || subcommands_.empty()) {
            missing_.emplace_back(val_type, val);
            return;
        }
        // allow extra arguments to be places in an option group if it is allowed there
        for(auto &subc : subcommands_) {
            if(subc->name_.empty() && subc->allow_extras_) {
                subc->missing_.emplace_back(val_type, val);
                return;
            }
        }
        // if we haven't found any place to put them yet put them in missing
        missing_.emplace_back(val_type, val);
    }

  public:
    /// function that could be used by subclasses of App to shift options around into subcommands
    void _move_option(Option *opt, App *app) {
        if(opt == nullptr) {
            throw OptionNotFound("the option is NULL");
        }
        // verify that the give app is actually a subcommand
        bool found = false;
        for(auto &subc : subcommands_) {
            if(app == subc.get()) {
                found = true;
            }
        }
        if(!found) {
            throw OptionNotFound("The Given app is not a subcommand");
        }

        if((help_ptr_ == opt) || (help_all_ptr_ == opt))
            throw OptionAlreadyAdded("cannot move help options");

        if(config_ptr_ == opt)
            throw OptionAlreadyAdded("cannot move config file options");

        auto iterator =
            std::find_if(std::begin(options_), std::end(options_), [opt](const Option_p &v) { return v.get() == opt; });
        if(iterator != std::end(options_)) {
            const auto &opt_p = *iterator;
            if(std::find_if(std::begin(app->options_), std::end(app->options_), [&opt_p](const Option_p &v) {
                   return (*v == *opt_p);
               }) == std::end(app->options_)) {
                // only erase after the insertion was successful
                app->options_.push_back(std::move(*iterator));
                options_.erase(iterator);
            } else {
                throw OptionAlreadyAdded("option was not located: " + opt->get_name());
            }
        } else {
            throw OptionNotFound("could not locate the given Option");
        }
    }
};  // namespace CLI

/// Extension of App to better manage groups of options
class Option_group : public App {
  public:
    Option_group(std::string group_description, std::string group_name, App *parent)
        : App(std::move(group_description), "", parent) {
        group(group_name);
        // option groups should have automatic fallthrough
    }
    using App::add_option;
    /// Add an existing option to the Option_group
    Option *add_option(Option *opt) {
        if(get_parent() == nullptr) {
            throw OptionNotFound("Unable to locate the specified option");
        }
        get_parent()->_move_option(opt, this);
        return opt;
    }
    /// Add an existing option to the Option_group
    void add_options(Option *opt) { add_option(opt); }
    /// Add a bunch of options to the group
    template <typename... Args> void add_options(Option *opt, Args... args) {
        add_option(opt);
        add_options(args...);
    }
    using App::add_subcommand;
    /// Add an existing subcommand to be a member of an option_group
    App *add_subcommand(App *subcom) {
        App_p subc = subcom->get_parent()->get_subcommand_ptr(subcom);
        subc->get_parent()->remove_subcommand(subcom);
        add_subcommand(std::move(subc));
        return subcom;
    }
};
/// Helper function to enable one option group/subcommand when another is used
inline void TriggerOn(App *trigger_app, App *app_to_enable) {
    app_to_enable->enabled_by_default(false);
    app_to_enable->disabled_by_default();
    trigger_app->preparse_callback([app_to_enable](std::size_t) { app_to_enable->disabled(false); });
}

/// Helper function to enable one option group/subcommand when another is used
inline void TriggerOn(App *trigger_app, std::vector<App *> apps_to_enable) {
    for(auto &app : apps_to_enable) {
        app->enabled_by_default(false);
        app->disabled_by_default();
    }

    trigger_app->preparse_callback([apps_to_enable](std::size_t) {
        for(auto &app : apps_to_enable) {
            app->disabled(false);
        }
    });
}

/// Helper function to disable one option group/subcommand when another is used
inline void TriggerOff(App *trigger_app, App *app_to_enable) {
    app_to_enable->disabled_by_default(false);
    app_to_enable->enabled_by_default();
    trigger_app->preparse_callback([app_to_enable](std::size_t) { app_to_enable->disabled(); });
}

/// Helper function to disable one option group/subcommand when another is used
inline void TriggerOff(App *trigger_app, std::vector<App *> apps_to_enable) {
    for(auto &app : apps_to_enable) {
        app->disabled_by_default(false);
        app->enabled_by_default();
    }

    trigger_app->preparse_callback([apps_to_enable](std::size_t) {
        for(auto &app : apps_to_enable) {
            app->disabled();
        }
    });
}

/// Helper function to mark an option as deprecated
inline void deprecate_option(Option *opt, const std::string &replacement = "") {
    Validator deprecate_warning{[opt, replacement](std::string &) {
                                    std::cout << opt->get_name() << " is deprecated please use '" << replacement
                                              << "' instead\n";
                                    return std::string();
                                },
                                "DEPRECATED"};
    deprecate_warning.application_index(0);
    opt->check(deprecate_warning);
    if(!replacement.empty()) {
        opt->description(opt->get_description() + " DEPRECATED: please use '" + replacement + "' instead");
    }
}

/// Helper function to mark an option as deprecated
inline void deprecate_option(App *app, const std::string &option_name, const std::string &replacement = "") {
    auto opt = app->get_option(option_name);
    deprecate_option(opt, replacement);
}

/// Helper function to mark an option as deprecated
inline void deprecate_option(App &app, const std::string &option_name, const std::string &replacement = "") {
    auto opt = app.get_option(option_name);
    deprecate_option(opt, replacement);
}

/// Helper function to mark an option as retired
inline void retire_option(App *app, Option *opt) {
    App temp;
    auto option_copy = temp.add_option(opt->get_name(false, true))
                           ->type_size(opt->get_type_size_min(), opt->get_type_size_max())
                           ->expected(opt->get_expected_min(), opt->get_expected_max())
                           ->allow_extra_args(opt->get_allow_extra_args());

    app->remove_option(opt);
    auto opt2 = app->add_option(option_copy->get_name(false, true), "option has been retired and has no effect")
                    ->type_name("RETIRED")
                    ->default_str("RETIRED")
                    ->type_size(option_copy->get_type_size_min(), option_copy->get_type_size_max())
                    ->expected(option_copy->get_expected_min(), option_copy->get_expected_max())
                    ->allow_extra_args(option_copy->get_allow_extra_args());

    Validator retired_warning{[opt2](std::string &) {
                                  std::cout << "WARNING " << opt2->get_name() << " is retired and has no effect\n";
                                  return std::string();
                              },
                              ""};
    retired_warning.application_index(0);
    opt2->check(retired_warning);
}

/// Helper function to mark an option as retired
inline void retire_option(App &app, Option *opt) { retire_option(&app, opt); }

/// Helper function to mark an option as retired
inline void retire_option(App *app, const std::string &option_name) {

    auto opt = app->get_option_no_throw(option_name);
    if(opt != nullptr) {
        retire_option(app, opt);
        return;
    }
    auto opt2 = app->add_option(option_name, "option has been retired and has no effect")
                    ->type_name("RETIRED")
                    ->expected(0, 1)
                    ->default_str("RETIRED");
    Validator retired_warning{[opt2](std::string &) {
                                  std::cout << "WARNING " << opt2->get_name() << " is retired and has no effect\n";
                                  return std::string();
                              },
                              ""};
    retired_warning.application_index(0);
    opt2->check(retired_warning);
}

/// Helper function to mark an option as retired
inline void retire_option(App &app, const std::string &option_name) { retire_option(&app, option_name); }

namespace FailureMessage {

/// Printout a clean, simple message on error (the default in CLI11 1.5+)
inline std::string simple(const App *app, const Error &e) {
    std::string header = std::string(e.what()) + "\n";
    std::vector<std::string> names;

    // Collect names
    if(app->get_help_ptr() != nullptr)
        names.push_back(app->get_help_ptr()->get_name());

    if(app->get_help_all_ptr() != nullptr)
        names.push_back(app->get_help_all_ptr()->get_name());

    // If any names found, suggest those
    if(!names.empty())
        header += "Run with " + detail::join(names, " or ") + " for more information.\n";

    return header;
}

/// Printout the full help string on error (if this fn is set, the old default for CLI11)
inline std::string help(const App *app, const Error &e) {
    std::string header = std::string("ERROR: ") + e.get_name() + ": " + e.what() + "\n";
    header += app->help();
    return header;
}

}  // namespace FailureMessage

namespace detail {
/// This class is simply to allow tests access to App's protected functions
struct AppFriend {
#ifdef CLI11_CPP14

    /// Wrap _parse_short, perfectly forward arguments and return
    template <typename... Args> static decltype(auto) parse_arg(App *app, Args &&... args) {
        return app->_parse_arg(std::forward<Args>(args)...);
    }

    /// Wrap _parse_subcommand, perfectly forward arguments and return
    template <typename... Args> static decltype(auto) parse_subcommand(App *app, Args &&... args) {
        return app->_parse_subcommand(std::forward<Args>(args)...);
    }
#else
    /// Wrap _parse_short, perfectly forward arguments and return
    template <typename... Args>
    static auto parse_arg(App *app, Args &&... args) ->
        typename std::result_of<decltype (&App::_parse_arg)(App, Args...)>::type {
        return app->_parse_arg(std::forward<Args>(args)...);
    }

    /// Wrap _parse_subcommand, perfectly forward arguments and return
    template <typename... Args>
    static auto parse_subcommand(App *app, Args &&... args) ->
        typename std::result_of<decltype (&App::_parse_subcommand)(App, Args...)>::type {
        return app->_parse_subcommand(std::forward<Args>(args)...);
    }
#endif
    /// Wrap the fallthrough parent function to make sure that is working correctly
    static App *get_fallthrough_parent(App *app) { return app->_get_fallthrough_parent(); }
};
}  // namespace detail


namespace detail {

inline std::string convert_arg_for_ini(const std::string &arg, char stringQuote = '"', char characterQuote = '\'') {
    if(arg.empty()) {
        return std::string(2, stringQuote);
    }
    // some specifically supported strings
    if(arg == "true" || arg == "false" || arg == "nan" || arg == "inf") {
        return arg;
    }
    // floating point conversion can convert some hex codes, but don't try that here
    if(arg.compare(0, 2, "0x") != 0 && arg.compare(0, 2, "0X") != 0) {
        double val;
        if(detail::lexical_cast(arg, val)) {
            return arg;
        }
    }
    // just quote a single non numeric character
    if(arg.size() == 1) {
        return std::string(1, characterQuote) + arg + characterQuote;
    }
    // handle hex, binary or octal arguments
    if(arg.front() == '0') {
        if(arg[1] == 'x') {
            if(std::all_of(arg.begin() + 2, arg.end(), [](char x) {
                   return (x >= '0' && x <= '9') || (x >= 'A' && x <= 'F') || (x >= 'a' && x <= 'f');
               })) {
                return arg;
            }
        } else if(arg[1] == 'o') {
            if(std::all_of(arg.begin() + 2, arg.end(), [](char x) { return (x >= '0' && x <= '7'); })) {
                return arg;
            }
        } else if(arg[1] == 'b') {
            if(std::all_of(arg.begin() + 2, arg.end(), [](char x) { return (x == '0' || x == '1'); })) {
                return arg;
            }
        }
    }
    if(arg.find_first_of(stringQuote) == std::string::npos) {
        return std::string(1, stringQuote) + arg + stringQuote;
    } else {
        return characterQuote + arg + characterQuote;
    }
}

/// Comma separated join, adds quotes if needed
inline std::string ini_join(const std::vector<std::string> &args,
                            char sepChar = ',',
                            char arrayStart = '[',
                            char arrayEnd = ']',
                            char stringQuote = '"',
                            char characterQuote = '\'') {
    std::string joined;
    if(args.size() > 1 && arrayStart != '\0') {
        joined.push_back(arrayStart);
    }
    std::size_t start = 0;
    for(const auto &arg : args) {
        if(start++ > 0) {
            joined.push_back(sepChar);
            if(isspace(sepChar) == 0) {
                joined.push_back(' ');
            }
        }
        joined.append(convert_arg_for_ini(arg, stringQuote, characterQuote));
    }
    if(args.size() > 1 && arrayEnd != '\0') {
        joined.push_back(arrayEnd);
    }
    return joined;
}

inline std::vector<std::string> generate_parents(const std::string &section, std::string &name) {
    std::vector<std::string> parents;
    if(detail::to_lower(section) != "default") {
        if(section.find('.') != std::string::npos) {
            parents = detail::split(section, '.');
        } else {
            parents = {section};
        }
    }
    if(name.find('.') != std::string::npos) {
        std::vector<std::string> plist = detail::split(name, '.');
        name = plist.back();
        detail::remove_quotes(name);
        plist.pop_back();
        parents.insert(parents.end(), plist.begin(), plist.end());
    }

    // clean up quotes on the parents
    for(auto &parent : parents) {
        detail::remove_quotes(parent);
    }
    return parents;
}

/// assuming non default segments do a check on the close and open of the segments in a configItem structure
inline void checkParentSegments(std::vector<ConfigItem> &output, const std::string &currentSection) {

    std::string estring;
    auto parents = detail::generate_parents(currentSection, estring);
    if(!output.empty() && output.back().name == "--") {
        std::size_t msize = (parents.size() > 1U) ? parents.size() : 2;
        while(output.back().parents.size() >= msize) {
            output.push_back(output.back());
            output.back().parents.pop_back();
        }

        if(parents.size() > 1) {
            std::size_t common = 0;
            std::size_t mpair = (std::min)(output.back().parents.size(), parents.size() - 1);
            for(std::size_t ii = 0; ii < mpair; ++ii) {
                if(output.back().parents[ii] != parents[ii]) {
                    break;
                }
                ++common;
            }
            if(common == mpair) {
                output.pop_back();
            } else {
                while(output.back().parents.size() > common + 1) {
                    output.push_back(output.back());
                    output.back().parents.pop_back();
                }
            }
            for(std::size_t ii = common; ii < parents.size() - 1; ++ii) {
                output.emplace_back();
                output.back().parents.assign(parents.begin(), parents.begin() + static_cast<std::ptrdiff_t>(ii) + 1);
                output.back().name = "++";
            }
        }
    } else if(parents.size() > 1) {
        for(std::size_t ii = 0; ii < parents.size() - 1; ++ii) {
            output.emplace_back();
            output.back().parents.assign(parents.begin(), parents.begin() + static_cast<std::ptrdiff_t>(ii) + 1);
            output.back().name = "++";
        }
    }

    // insert a section end which is just an empty items_buffer
    output.emplace_back();
    output.back().parents = std::move(parents);
    output.back().name = "++";
}
}  // namespace detail

inline std::vector<ConfigItem> ConfigBase::from_config(std::istream &input) const {
    std::string line;
    std::string section = "default";

    std::vector<ConfigItem> output;
    bool isDefaultArray = (arrayStart == '[' && arrayEnd == ']' && arraySeparator == ',');
    bool isINIArray = (arrayStart == '\0' || arrayStart == ' ') && arrayStart == arrayEnd;
    char aStart = (isINIArray) ? '[' : arrayStart;
    char aEnd = (isINIArray) ? ']' : arrayEnd;
    char aSep = (isINIArray && arraySeparator == ' ') ? ',' : arraySeparator;

    while(getline(input, line)) {
        std::vector<std::string> items_buffer;
        std::string name;

        detail::trim(line);
        std::size_t len = line.length();
        if(len > 1 && line.front() == '[' && line.back() == ']') {
            if(section != "default") {
                // insert a section end which is just an empty items_buffer
                output.emplace_back();
                output.back().parents = detail::generate_parents(section, name);
                output.back().name = "--";
            }
            section = line.substr(1, len - 2);
            // deal with double brackets for TOML
            if(section.size() > 1 && section.front() == '[' && section.back() == ']') {
                section = section.substr(1, section.size() - 2);
            }
            if(detail::to_lower(section) == "default") {
                section = "default";
            } else {
                detail::checkParentSegments(output, section);
            }
            continue;
        }
        if(len == 0) {
            continue;
        }
        // comment lines
        if(line.front() == ';' || line.front() == '#' || line.front() == commentChar) {
            continue;
        }

        // Find = in string, split and recombine
        auto pos = line.find(valueDelimiter);
        if(pos != std::string::npos) {
            name = detail::trim_copy(line.substr(0, pos));
            std::string item = detail::trim_copy(line.substr(pos + 1));
            if(item.size() > 1 && item.front() == aStart) {
                for(std::string multiline; item.back() != aEnd && std::getline(input, multiline);) {
                    detail::trim(multiline);
                    item += multiline;
                }
                items_buffer = detail::split_up(item.substr(1, item.length() - 2), aSep);
            } else if((isDefaultArray || isINIArray) && item.find_first_of(aSep) != std::string::npos) {
                items_buffer = detail::split_up(item, aSep);
            } else if((isDefaultArray || isINIArray) && item.find_first_of(' ') != std::string::npos) {
                items_buffer = detail::split_up(item);
            } else {
                items_buffer = {item};
            }
        } else {
            name = detail::trim_copy(line);
            items_buffer = {"true"};
        }
        if(name.find('.') == std::string::npos) {
            detail::remove_quotes(name);
        }
        // clean up quotes on the items
        for(auto &it : items_buffer) {
            detail::remove_quotes(it);
        }

        std::vector<std::string> parents = detail::generate_parents(section, name);

        if(!output.empty() && name == output.back().name && parents == output.back().parents) {
            output.back().inputs.insert(output.back().inputs.end(), items_buffer.begin(), items_buffer.end());
        } else {
            output.emplace_back();
            output.back().parents = std::move(parents);
            output.back().name = std::move(name);
            output.back().inputs = std::move(items_buffer);
        }
    }
    if(section != "default") {
        // insert a section end which is just an empty items_buffer
        std::string ename;
        output.emplace_back();
        output.back().parents = detail::generate_parents(section, ename);
        output.back().name = "--";
        while(output.back().parents.size() > 1) {
            output.push_back(output.back());
            output.back().parents.pop_back();
        }
    }
    return output;
}

inline std::string
ConfigBase::to_config(const App *app, bool default_also, bool write_description, std::string prefix) const {
    std::stringstream out;
    std::string commentLead;
    commentLead.push_back(commentChar);
    commentLead.push_back(' ');

    std::vector<std::string> groups = app->get_groups();
    bool defaultUsed = false;
    groups.insert(groups.begin(), std::string("Options"));
    if(write_description && (app->get_configurable() || app->get_parent() == nullptr || app->get_name().empty())) {
        out << commentLead << detail::fix_newlines(commentLead, app->get_description()) << '\n';
    }
    for(auto &group : groups) {
        if(group == "Options" || group.empty()) {
            if(defaultUsed) {
                continue;
            }
            defaultUsed = true;
        }
        if(write_description && group != "Options" && !group.empty()) {
            out << '\n' << commentLead << group << " Options\n";
        }
        for(const Option *opt : app->get_options({})) {

            // Only process options that are configurable
            if(opt->get_configurable()) {
                if(opt->get_group() != group) {
                    if(!(group == "Options" && opt->get_group().empty())) {
                        continue;
                    }
                }
                std::string name = prefix + opt->get_single_name();
                std::string value = detail::ini_join(
                    opt->reduced_results(), arraySeparator, arrayStart, arrayEnd, stringQuote, characterQuote);

                if(value.empty() && default_also) {
                    if(!opt->get_default_str().empty()) {
                        value = detail::convert_arg_for_ini(opt->get_default_str(), stringQuote, characterQuote);
                    } else if(opt->get_expected_min() == 0) {
                        value = "false";
                    } else if(opt->get_run_callback_for_default()) {
                        value = "\"\"";  // empty string default value
                    }
                }

                if(!value.empty()) {
                    if(write_description && opt->has_description()) {
                        out << '\n';
                        out << commentLead << detail::fix_newlines(commentLead, opt->get_description()) << '\n';
                    }
                    out << name << valueDelimiter << value << '\n';
                }
            }
        }
    }
    auto subcommands = app->get_subcommands({});
    for(const App *subcom : subcommands) {
        if(subcom->get_name().empty()) {
            if(write_description && !subcom->get_group().empty()) {
                out << '\n' << commentLead << subcom->get_group() << " Options\n";
            }
            out << to_config(subcom, default_also, write_description, prefix);
        }
    }

    for(const App *subcom : subcommands) {
        if(!subcom->get_name().empty()) {
            if(subcom->get_configurable() && app->got_subcommand(subcom)) {
                if(!prefix.empty() || app->get_parent() == nullptr) {
                    out << '[' << prefix << subcom->get_name() << "]\n";
                } else {
                    std::string subname = app->get_name() + "." + subcom->get_name();
                    auto p = app->get_parent();
                    while(p->get_parent() != nullptr) {
                        subname = p->get_name() + "." + subname;
                        p = p->get_parent();
                    }
                    out << '[' << subname << "]\n";
                }
                out << to_config(subcom, default_also, write_description, "");
            } else {
                out << to_config(subcom, default_also, write_description, prefix + subcom->get_name() + ".");
            }
        }
    }

    return out.str();
}


inline std::string
Formatter::make_group(std::string group, bool is_positional, std::vector<const Option *> opts) const {
    std::stringstream out;

    out << "\n" << group << ":\n";
    for(const Option *opt : opts) {
        out << make_option(opt, is_positional);
    }

    return out.str();
}

inline std::string Formatter::make_positionals(const App *app) const {
    std::vector<const Option *> opts =
        app->get_options([](const Option *opt) { return !opt->get_group().empty() && opt->get_positional(); });

    if(opts.empty())
        return std::string();

    return make_group(get_label("Positionals"), true, opts);
}

inline std::string Formatter::make_groups(const App *app, AppFormatMode mode) const {
    std::stringstream out;
    std::vector<std::string> groups = app->get_groups();

    // Options
    for(const std::string &group : groups) {
        std::vector<const Option *> opts = app->get_options([app, mode, &group](const Option *opt) {
            return opt->get_group() == group                     // Must be in the right group
                   && opt->nonpositional()                       // Must not be a positional
                   && (mode != AppFormatMode::Sub                // If mode is Sub, then
                       || (app->get_help_ptr() != opt            // Ignore help pointer
                           && app->get_help_all_ptr() != opt));  // Ignore help all pointer
        });
        if(!group.empty() && !opts.empty()) {
            out << make_group(group, false, opts);

            if(group != groups.back())
                out << "\n";
        }
    }

    return out.str();
}

inline std::string Formatter::make_description(const App *app) const {
    std::string desc = app->get_description();
    auto min_options = app->get_require_option_min();
    auto max_options = app->get_require_option_max();
    if(app->get_required()) {
        desc += " REQUIRED ";
    }
    if((max_options == min_options) && (min_options > 0)) {
        if(min_options == 1) {
            desc += " \n[Exactly 1 of the following options is required]";
        } else {
            desc += " \n[Exactly " + std::to_string(min_options) + "options from the following list are required]";
        }
    } else if(max_options > 0) {
        if(min_options > 0) {
            desc += " \n[Between " + std::to_string(min_options) + " and " + std::to_string(max_options) +
                    " of the follow options are required]";
        } else {
            desc += " \n[At most " + std::to_string(max_options) + " of the following options are allowed]";
        }
    } else if(min_options > 0) {
        desc += " \n[At least " + std::to_string(min_options) + " of the following options are required]";
    }
    return (!desc.empty()) ? desc + "\n" : std::string{};
}

inline std::string Formatter::make_usage(const App *app, std::string name) const {
    std::stringstream out;

    out << get_label("Usage") << ":" << (name.empty() ? "" : " ") << name;

    std::vector<std::string> groups = app->get_groups();

    // Print an Options badge if any options exist
    std::vector<const Option *> non_pos_options =
        app->get_options([](const Option *opt) { return opt->nonpositional(); });
    if(!non_pos_options.empty())
        out << " [" << get_label("OPTIONS") << "]";

    // Positionals need to be listed here
    std::vector<const Option *> positionals = app->get_options([](const Option *opt) { return opt->get_positional(); });

    // Print out positionals if any are left
    if(!positionals.empty()) {
        // Convert to help names
        std::vector<std::string> positional_names(positionals.size());
        std::transform(positionals.begin(), positionals.end(), positional_names.begin(), [this](const Option *opt) {
            return make_option_usage(opt);
        });

        out << " " << detail::join(positional_names, " ");
    }

    // Add a marker if subcommands are expected or optional
    if(!app->get_subcommands(
               [](const CLI::App *subc) { return ((!subc->get_disabled()) && (!subc->get_name().empty())); })
            .empty()) {
        out << " " << (app->get_require_subcommand_min() == 0 ? "[" : "")
            << get_label(app->get_require_subcommand_max() < 2 || app->get_require_subcommand_min() > 1 ? "SUBCOMMAND"
                                                                                                        : "SUBCOMMANDS")
            << (app->get_require_subcommand_min() == 0 ? "]" : "");
    }

    out << std::endl;

    return out.str();
}

inline std::string Formatter::make_footer(const App *app) const {
    std::string footer = app->get_footer();
    if(footer.empty()) {
        return std::string{};
    }
    return footer + "\n";
}

inline std::string Formatter::make_help(const App *app, std::string name, AppFormatMode mode) const {

    // This immediately forwards to the make_expanded method. This is done this way so that subcommands can
    // have overridden formatters
    if(mode == AppFormatMode::Sub)
        return make_expanded(app);

    std::stringstream out;
    if((app->get_name().empty()) && (app->get_parent() != nullptr)) {
        if(app->get_group() != "Subcommands") {
            out << app->get_group() << ':';
        }
    }

    out << make_description(app);
    out << make_usage(app, name);
    out << make_positionals(app);
    out << make_groups(app, mode);
    out << make_subcommands(app, mode);
    out << '\n' << make_footer(app);

    return out.str();
}

inline std::string Formatter::make_subcommands(const App *app, AppFormatMode mode) const {
    std::stringstream out;

    std::vector<const App *> subcommands = app->get_subcommands({});

    // Make a list in definition order of the groups seen
    std::vector<std::string> subcmd_groups_seen;
    for(const App *com : subcommands) {
        if(com->get_name().empty()) {
            if(!com->get_group().empty()) {
                out << make_expanded(com);
            }
            continue;
        }
        std::string group_key = com->get_group();
        if(!group_key.empty() &&
           std::find_if(subcmd_groups_seen.begin(), subcmd_groups_seen.end(), [&group_key](std::string a) {
               return detail::to_lower(a) == detail::to_lower(group_key);
           }) == subcmd_groups_seen.end())
            subcmd_groups_seen.push_back(group_key);
    }

    // For each group, filter out and print subcommands
    for(const std::string &group : subcmd_groups_seen) {
        out << "\n" << group << ":\n";
        std::vector<const App *> subcommands_group = app->get_subcommands(
            [&group](const App *sub_app) { return detail::to_lower(sub_app->get_group()) == detail::to_lower(group); });
        for(const App *new_com : subcommands_group) {
            if(new_com->get_name().empty())
                continue;
            if(mode != AppFormatMode::All) {
                out << make_subcommand(new_com);
            } else {
                out << new_com->help(new_com->get_name(), AppFormatMode::Sub);
                out << "\n";
            }
        }
    }

    return out.str();
}

inline std::string Formatter::make_subcommand(const App *sub) const {
    std::stringstream out;
    detail::format_help(out, sub->get_display_name(true), sub->get_description(), column_width_);
    return out.str();
}

inline std::string Formatter::make_expanded(const App *sub) const {
    std::stringstream out;
    out << sub->get_display_name(true) << "\n";

    out << make_description(sub);
    if(sub->get_name().empty() && !sub->get_aliases().empty()) {
        detail::format_aliases(out, sub->get_aliases(), column_width_ + 2);
    }
    out << make_positionals(sub);
    out << make_groups(sub, AppFormatMode::Sub);
    out << make_subcommands(sub, AppFormatMode::Sub);

    // Drop blank spaces
    std::string tmp = detail::find_and_replace(out.str(), "\n\n", "\n");
    tmp = tmp.substr(0, tmp.size() - 1);  // Remove the final '\n'

    // Indent all but the first line (the name)
    return detail::find_and_replace(tmp, "\n", "\n  ") + "\n";
}

inline std::string Formatter::make_option_name(const Option *opt, bool is_positional) const {
    if(is_positional)
        return opt->get_name(true, false);

    return opt->get_name(false, true);
}

inline std::string Formatter::make_option_opts(const Option *opt) const {
    std::stringstream out;

    if(!opt->get_option_text().empty()) {
        out << " " << opt->get_option_text();
    } else {
        if(opt->get_type_size() != 0) {
            if(!opt->get_type_name().empty())
                out << " " << get_label(opt->get_type_name());
            if(!opt->get_default_str().empty())
                out << "=" << opt->get_default_str();
            if(opt->get_expected_max() == detail::expected_max_vector_size)
                out << " ...";
            else if(opt->get_expected_min() > 1)
                out << " x " << opt->get_expected();

            if(opt->get_required())
                out << " " << get_label("REQUIRED");
        }
        if(!opt->get_envname().empty())
            out << " (" << get_label("Env") << ":" << opt->get_envname() << ")";
        if(!opt->get_needs().empty()) {
            out << " " << get_label("Needs") << ":";
            for(const Option *op : opt->get_needs())
                out << " " << op->get_name();
        }
        if(!opt->get_excludes().empty()) {
            out << " " << get_label("Excludes") << ":";
            for(const Option *op : opt->get_excludes())
                out << " " << op->get_name();
        }
    }
    return out.str();
}

inline std::string Formatter::make_option_desc(const Option *opt) const { return opt->get_description(); }

inline std::string Formatter::make_option_usage(const Option *opt) const {
    // Note that these are positionals usages
    std::stringstream out;
    out << make_option_name(opt, true);
    if(opt->get_expected_max() >= detail::expected_max_vector_size)
        out << "...";
    else if(opt->get_expected_max() > 1)
        out << "(" << opt->get_expected() << "x)";

    return opt->get_required() ? out.str() : "[" + out.str() + "]";
}


} // namespace CLI