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This is a simple Go library to manage commands for your CLI tool.
Easy to use and now you can focus on Business Logic instead of building
the command routing.

### What this library does for you?

Manage your separated commands. How? Generates a general help and command
specific helps for your commands. If your command fails somewhere
(`panic` for example), commander will display the error message and
the command specific help to guide your user.

### Install

```shell
$ go get github.com/yitsushi/go-commander
```

### Sample output _(from [totp-cli](https://github.com/yitsushi/totp-cli))_

```shell
$ totp-cli help

change-password                   Change password
update                            Check and update totp-cli itself
version                           Print current version of this application
generate <namespace>.<account>    Generate a specific OTP
add-token [namespace] [account]   Add new token
list [namespace]                  List all available namespaces or accounts under a namespace
delete <namespace>[.account]      Delete an account or a whole namespace
help [command]                    Display this help or a command specific help
```

### Usage

Every single command has to implement `CommandHandler`.
Check [this project](https://github.com/yitsushi/totp-cli) for examples.

```go
package main

// Import the package
import "github.com/yitsushi/go-commander"

// Your Command
type YourCommand struct {
}

// Executed only on command call
func (c *YourCommand) Execute(opts *commander.CommandHelper) {
  // Command Action
}

func NewYourCommand(appName string) *commander.CommandWrapper {
  return &commander.CommandWrapper{
    Handler: &YourCommand{},
    Help: &commander.CommandDescriptor{
      Name:             "your-command",
      ShortDescription: "This is my own command",
      LongDescription:  `This is a very long
description about this command.`,
      Arguments:        "<filename> [optional-argument]",
      Examples:         []string {
        "test.txt",
        "test.txt copy",
        "test.txt move",
      },
    },
  }
}

// Main Section
func main() {
	registry := commander.NewCommandRegistry()

	registry.Register(NewYourCommand)

	registry.Execute()
}
```

Now you have a CLI tool with two commands: `help` and `your-command`.

```bash
❯ go build mytool.go

❯ ./mytool
your-command <filename> [optional-argument]   This is my own command
help [command]                                Display this help or a command specific help

❯ ./mytool help your-command
Usage: mytool your-command <filename> [optional-argument]

This is a very long
description about this command.

Examples:
  mytool your-command test.txt
  mytool your-command test.txt copy
  mytool your-command test.txt move
```

#### How to use subcommand pattern?

When you create your main command, just create a new `CommandRegistry` inside
the `Execute` function like you did in your `main()` and change `Depth`.

```go
import subcommand "github.com/yitsushi/mypackage/command/something"

func (c *Something) Execute(opts *commander.CommandHelper) {
	registry := commander.NewCommandRegistry()
	registry.Depth = 1
	registry.Register(subcommand.NewSomethingMySubCommand)
	registry.Execute()
}
```

### PreValidation

If you want to write a general pre-validation for your command
or just simply keep your validation logic separated:

```go
// Or you can define inline if you want
func MyValidator(c *commander.CommandHelper) {
  if c.Arg(0) == "" {
    panic("File?")
  }

  info, err := os.Stat(c.Arg(0))
  if err != nil {
    panic("File not found")
  }

  if !info.Mode().IsRegular() {
    panic("It's not a regular file")
  }

  if c.Arg(1) != "" {
    if c.Arg(1) != "copy" && c.Arg(1) != "move" {
      panic("Invalid operation")
    }
  }
}

func NewYourCommand(appName string) *commander.CommandWrapper {
  return &commander.CommandWrapper{
    Handler: &YourCommand{},
    Validator: MyValidator
    Help: &commander.CommandDescriptor{
      Name:             "your-command",
      ShortDescription: "This is my own command",
      LongDescription:  `This is a very long
description about this command.`,
      Arguments:        "<filename> [optional-argument]",
      Examples:         []string {
        "test.txt",
        "test.txt copy",
        "test.txt move",
      },
    },
  }
}
```


### Define arguments with type

```go
&commander.CommandWrapper{
  Handler: &MyCommand{},
  Arguments: []*commander.Argument{
    &commander.Argument{
      Name: "list",
      Type: "StringArray[]",
    },
  },
  Help: &commander.CommandDescriptor{
    Name: "my-command",
  },
}
```

In your command:

```go
if opts.HasValidTypedOpt("list") == nil {
  myList := opts.TypedOpt("list").([]string)
  if len(myList) > 0 {
    mockPrintf("My list: %v\n", myList)
  }
}
```

#### Define own type

Yes you can ;)

```go
// Define your struct (optional)
type MyCustomType struct {
	ID   uint64
	Name string
}

// register your own type with parsing/validation
commander.RegisterArgumentType("MyType", func(value string) (interface{}, error) {
  values := strings.Split(value, ":")

  if len(values) < 2 {
    return &MyCustomType{}, errors.New("Invalid format! MyType => 'ID:Name'")
  }

  id, err := strconv.ParseUint(values[0], 10, 64)
  if err != nil {
    return &MyCustomType{}, errors.New("Invalid format! MyType => 'ID:Name'")
  }

  return &MyCustomType{
      ID:   id,
      Name: values[1],
    },
    nil
})

// Define your command
&commander.CommandWrapper{
  Handler: &MyCommand{},
  Arguments: []*commander.Argument{
    &commander.Argument{
      Name:        "owner",
      Type:        "MyType",
      FailOnError: true,          // Optional boolean
    },
  },
  Help: &commander.CommandDescriptor{
    Name: "my-command",
  },
}
```

In your command:

```go
if opts.HasValidTypedOpt("owner") == nil {
  owner := opts.TypedOpt("owner").(*MyCustomType)
  mockPrintf("OwnerID: %d, Name: %s\n", owner.ID, owner.Name)
}
```