<?php
/*
** Zabbix
** Copyright (C) 2001-2021 Zabbix SIA
**
** This program is free software; you can redistribute it and/or modify
** it under the terms of the GNU General Public License as published by
** the Free Software Foundation; either version 2 of the License, or
** (at your option) any later version.
**
** This program is distributed in the hope that it will be useful,
** but WITHOUT ANY WARRANTY; without even the implied warranty of
** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
** GNU General Public License for more details.
**
** You should have received a copy of the GNU General Public License
** along with this program; if not, write to the Free Software
** Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
**/


/**
 * API validator
 */
class CApiInputValidator {

	/**
	 * Base validation function.
	 *
	 * @param array  $rule  validation rule
	 * @param mixed  $data  import data
	 * @param string $path  data path (for error reporting)
	 * @param string $error
	 *
	 * @return bool
	 */
	public static function validate(array $rule, &$data, $path, &$error) {
		$error = '';

		return self::validateData($rule, $data, $path, $error)
			&& self::validateDataUniqueness($rule, $data, $path, $error);
	}

	/**
	 * Base uniqueness validation function.
	 *
	 * @param array  $rule  validation rule
	 * @param mixed  $data  import data
	 * @param string $path  data path (for error reporting)
	 * @param string $error
	 *
	 * @return bool
	 */
	public static function validateUniqueness(array $rule, $data, $path, &$error) {
		$error = '';

		return self::validateDataUniqueness($rule, $data, $path, $error);
	}

	/**
	 * Base data validation function.
	 *
	 * @param array  $rule
	 * @param mixed  $data
	 * @param string $path
	 * @param string $error
	 * @param array  $parent_data
	 *
	 * @return bool
	 */
	private static function validateData($rule, &$data, $path, &$error, array $parent_data = null) {
		switch ($rule['type']) {
			case API_CALC_FORMULA:
				return self::validateCalcFormula($rule, $data, $path, $error);

			case API_COLOR:
				return self::validateColor($rule, $data, $path, $error);

			case API_MULTIPLE:
				if ($parent_data !== null) {
					return self::validateMultiple($rule, $data, $path, $error, $parent_data);
				}
				break;

			case API_STRING_UTF8:
				return self::validateStringUtf8($rule, $data, $path, $error);

			case API_STRINGS_UTF8:
				return self::validateStringsUtf8($rule, $data, $path, $error);

			case API_INT32:
				return self::validateInt32($rule, $data, $path, $error);

			case API_INTS32:
				return self::validateInts32($rule, $data, $path, $error);

			case API_UINT64:
				return self::validateUInt64($rule, $data, $path, $error);

			case API_UINTS64:
				return self::validateUInts64($rule, $data, $path, $error);

			case API_FLOAT:
				return self::validateFloat($rule, $data, $path, $error);

			case API_FLOATS:
				return self::validateFloats($rule, $data, $path, $error);

			case API_ID:
				return self::validateId($rule, $data, $path, $error);

			case API_BOOLEAN:
				return self::validateBoolean($rule, $data, $path, $error);

			case API_FLAG:
				return self::validateFlag($rule, $data, $path, $error);

			case API_OBJECT:
				return self::validateObject($rule, $data, $path, $error);

			case API_OUTPUT:
				return self::validateOutput($rule, $data, $path, $error);

			case API_PSK:
				return self::validatePSK($rule, $data, $path, $error);

			case API_SORTORDER:
				return self::validateSortOrder($rule, $data, $path, $error);

			case API_IDS:
				return self::validateIds($rule, $data, $path, $error);

			case API_OBJECTS:
				return self::validateObjects($rule, $data, $path, $error);

			case API_HG_NAME:
				return self::validateHostGroupName($rule, $data, $path, $error);

			case API_H_NAME:
				return self::validateHostName($rule, $data, $path, $error);

			case API_NUMERIC:
				return self::validateNumeric($rule, $data, $path, $error);

			case API_SCRIPT_NAME:
				return self::validateScriptName($rule, $data, $path, $error);

			case API_USER_MACRO:
				return self::validateUserMacro($rule, $data, $path, $error);

			case API_LLD_MACRO:
				return self::validateLLDMacro($rule, $data, $path, $error);

			case API_RANGE_TIME:
				return self::validateRangeTime($rule, $data, $path, $error);

			case API_TIME_PERIOD:
				return self::validateTimePeriod($rule, $data, $path, $error);

			case API_REGEX:
				return self::validateRegex($rule, $data, $path, $error);

			case API_HTTP_POST:
				return self::validateHttpPosts($rule, $data, $path, $error);

			case API_VARIABLE_NAME:
				return self::validateVariableName($rule, $data, $path, $error);

			case API_TIME_UNIT:
				return self::validateTimeUnit($rule, $data, $path, $error);

			case API_URL:
				return self::validateUrl($rule, $data, $path, $error);

			case API_TRIGGER_EXPRESSION:
				return self::validateTriggerExpression($rule, $data, $path, $error);

			case API_JSONRPC_PARAMS:
				return self::validateJsonRpcParams($rule, $data, $path, $error);

			case API_JSONRPC_ID:
				return self::validateJsonRpcId($rule, $data, $path, $error);
		}

		// This message can be untranslated because warn about incorrect validation rules at a development stage.
		$error = 'Incorrect validation rules.';

		return false;
	}

	/**
	 * Base data uniqueness validation function.
	 *
	 * @param array  $rule
	 * @param mixed  $data
	 * @param string $path
	 * @param string $error
	 *
	 * @return bool
	 */
	private static function validateDataUniqueness($rule, &$data, $path, &$error) {
		switch ($rule['type']) {
			case API_CALC_FORMULA:
			case API_COLOR:
			case API_MULTIPLE:
			case API_STRING_UTF8:
			case API_INT32:
			case API_UINT64:
			case API_UINTS64:
			case API_FLOAT:
			case API_FLOATS:
			case API_ID:
			case API_BOOLEAN:
			case API_FLAG:
			case API_OUTPUT:
			case API_PSK:
			case API_SORTORDER:
			case API_HG_NAME:
			case API_H_NAME:
			case API_NUMERIC:
			case API_SCRIPT_NAME:
			case API_USER_MACRO:
			case API_LLD_MACRO:
			case API_RANGE_TIME:
			case API_TIME_PERIOD:
			case API_TIME_UNIT:
			case API_REGEX:
			case API_HTTP_POST:
			case API_VARIABLE_NAME:
			case API_URL:
			case API_TRIGGER_EXPRESSION:
			case API_JSONRPC_PARAMS:
			case API_JSONRPC_ID:
				return true;

			case API_OBJECT:
				foreach ($rule['fields'] as $field_name => $field_rule) {
					if ($data !== null && array_key_exists($field_name, $data)) {
						$subpath = ($path === '/' ? $path : $path.'/').$field_name;
						if (!self::validateDataUniqueness($field_rule, $data[$field_name], $subpath, $error)) {
							return false;
						}
					}
				}
				return true;

			case API_IDS:
			case API_STRINGS_UTF8:
			case API_INTS32:
				return self::validateStringsUniqueness($rule, $data, $path, $error);

			case API_OBJECTS:
				return self::validateObjectsUniqueness($rule, $data, $path, $error);
		}

		// This message can be untranslated because warn about incorrect validation rules at a development stage.
		$error = 'Incorrect validation rules.';

		return false;
	}

	/**
	 * Generic string validator.
	 *
	 * @param int    $flags  API_NOT_EMPTY
	 * @param mixed  $data
	 * @param string $path
	 * @param string $error
	 *
	 * @return bool
	 */
	private static function checkStringUtf8($flags, &$data, $path, &$error) {
		if (!is_string($data)) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('a character string is expected'));
			return false;
		}

		if (mb_check_encoding($data, 'UTF-8') !== true) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('invalid byte sequence in UTF-8'));
			return false;
		}

		if (($flags & API_NOT_EMPTY) && $data === '') {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('cannot be empty'));
			return false;
		}

		return true;
	}

	/**
	 * Calculated item formula validator.
	 *
	 * @param array  $rule
	 * @param int    $rule['flags']   (optional) API_ALLOW_LLD_MACRO
	 * @param mixed  $data
	 * @param string $path
	 * @param string $error
	 *
	 * @return bool
	 */
	private static function validateCalcFormula($rule, &$data, $path, &$error) {
		$flags = array_key_exists('flags', $rule) ? $rule['flags'] : 0x00;

		if (self::checkStringUtf8(API_NOT_EMPTY, $data, $path, $error) === false) {
			return false;
		}

		$expression_data = new CTriggerExpression(['calculated' => true, 'lldmacros' => ($flags & API_ALLOW_LLD_MACRO)]);
		if (!$expression_data->parse($data)) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, $expression_data->error);
			return false;
		}

		return true;
	}

	/**
	 * Color validator.
	 *
	 * @param array  $rule
	 * @param int    $rule['flags']   (optional) API_NOT_EMPTY
	 * @param mixed  $data
	 * @param string $path
	 * @param string $error
	 *
	 * @return bool
	 */
	private static function validateColor($rule, &$data, $path, &$error) {
		$flags = array_key_exists('flags', $rule) ? $rule['flags'] : 0x00;

		if (self::checkStringUtf8($flags & API_NOT_EMPTY, $data, $path, $error) === false) {
			return false;
		}

		if (($flags & API_NOT_EMPTY) == 0 && $data === '') {
			return true;
		}

		if (preg_match('/^[0-9a-f]{6}$/i', $data) !== 1) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path,
				_('a hexadecimal colour code (6 symbols) is expected')
			);
			return false;
		}

		return true;
	}

	/**
	 * Multiple data types validator.
	 *
	 * @param array  $rule
	 * @param array  $rule['rules']
	 * @param mixed  $data
	 * @param string $path
	 * @param string $error
	 * @param array  $parent_data
	 *
	 * @return bool
	 */
	private static function validateMultiple($rule, &$data, $path, &$error, array $parent_data) {
		foreach ($rule['rules'] as $field_rule) {
			if (self::Int32In($parent_data[$field_rule['if']['field']], $field_rule['if']['in'])) {
				unset($field_rule['if']);

				return self::validateData($field_rule, $data, $path, $error);
			}
		}

		// This message can be untranslated because warn about incorrect validation rules at a development stage.
		$error = 'Incorrect validation rules.';

		return false;
	}

	/**
	 * String validator.
	 *
	 * @param array  $rule
	 * @param int    $rule['flags']   (optional) API_NOT_EMPTY, API_ALLOW_NULL
	 * @param string $rule['in']      (optional) a comma-delimited character string, for example: 'xml,json'
	 * @param int    $rule['length']  (optional)
	 * @param mixed  $data
	 * @param string $path
	 * @param string $error
	 *
	 * @return bool
	 */
	private static function validateStringUtf8($rule, &$data, $path, &$error) {
		$flags = array_key_exists('flags', $rule) ? $rule['flags'] : 0x00;

		if (($flags & API_ALLOW_NULL) && $data === null) {
			return true;
		}

		if (self::checkStringUtf8($flags, $data, $path, $error) === false) {
			return false;
		}

		if (array_key_exists('in', $rule) && !in_array($data, explode(',', $rule['in']), true)) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path,
				_s('value must be one of %1$s', str_replace(',', ', ', $rule['in']))
			);
			return false;
		}

		if (array_key_exists('length', $rule) && mb_strlen($data) > $rule['length']) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('value is too long'));
			return false;
		}

		return true;
	}

	/**
	 * Array of strings validator.
	 *
	 * @param array  $rule
	 * @param int    $rule['flags']   (optional) API_NOT_EMPTY, API_ALLOW_NULL, API_NORMALIZE
	 * @param string $rule['in']      (optional) a comma-delimited character string, for example: 'xml,json'
	 * @param mixed  $data
	 * @param string $path
	 * @param string $error
	 *
	 * @return bool
	 */
	private static function validateStringsUtf8($rule, &$data, $path, &$error) {
		$flags = array_key_exists('flags', $rule) ? $rule['flags'] : 0x00;

		if (($flags & API_ALLOW_NULL) && $data === null) {
			return true;
		}

		if (($flags & API_NORMALIZE) && self::validateStringUtf8([], $data, '', $e)) {
			$data = [$data];
		}
		unset($e);

		if (!is_array($data)) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('an array is expected'));
			return false;
		}

		if (($flags & API_NOT_EMPTY) && !$data) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('cannot be empty'));
			return false;
		}

		$data = array_values($data);
		$rules = ['type' => API_STRING_UTF8];

		if (array_key_exists('in', $rule)) {
			$rules['in'] = $rule['in'];
		}

		foreach ($data as $index => &$value) {
			$subpath = ($path === '/' ? $path : $path.'/').($index + 1);
			if (!self::validateData($rules, $value, $subpath, $error)) {
				return false;
			}
		}
		unset($value);

		return true;
	}

	/**
	 * Integers validator.
	 *
	 * @param array  $rule
	 * @param int    $rule['flags']   (optional) API_ALLOW_NULL
	 * @param string $rule['in']      (optional) a comma-delimited character string, for example: '0,60:900'
	 * @param mixed  $data
	 * @param string $path
	 * @param string $error
	 *
	 * @return bool
	 */
	private static function validateInt32($rule, &$data, $path, &$error) {
		$flags = array_key_exists('flags', $rule) ? $rule['flags'] : 0x00;

		if (($flags & API_ALLOW_NULL) && $data === null) {
			return true;
		}

		if ((!is_int($data) && !is_string($data)) || !preg_match('/^'.ZBX_PREG_INT.'$/', strval($data))) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('an integer is expected'));
			return false;
		}

		if ($data < ZBX_MIN_INT32 || $data > ZBX_MAX_INT32) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('a number is too large'));
			return false;
		}

		if (!self::checkInt32In($rule, $data, $path, $error)) {
			return false;
		}

		if (is_string($data)) {
			$data = (int) $data;
		}

		return true;
	}

	/**
	 * Unsigned integers validator.
	 *
	 * @param array  $rule
	 * @param int    $rule['flags']   (optional) API_ALLOW_NULL
	 * @param mixed  $data
	 * @param string $path
	 * @param string $error
	 *
	 * @return bool
	 */
	private static function validateUInt64($rule, &$data, $path, &$error) {
		$flags = array_key_exists('flags', $rule) ? $rule['flags'] : 0x00;

		if (($flags & API_ALLOW_NULL) && $data === null) {
			return true;
		}

		if (!is_scalar($data) || is_bool($data) || is_double($data) || !ctype_digit(strval($data))) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('an unsigned integer is expected'));
			return false;
		}

		if (bccomp($data, ZBX_MAX_UINT64) > 0) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('a number is too large'));
			return false;
		}

		$data = (string) $data;

		if ($data[0] === '0') {
			$data = ltrim($data, '0');

			if ($data === '') {
				$data = '0';
			}
		}

		return true;
	}

	/**
	 * Array of unsigned integers validator.
	 *
	 * @param array  $rule
	 * @param int    $rule['flags']   (optional) API_NOT_EMPTY, API_ALLOW_NULL, API_NORMALIZE
	 * @param mixed  $data
	 * @param string $path
	 * @param string $error
	 *
	 * @return bool
	 */
	private static function validateUInts64($rule, &$data, $path, &$error) {
		$flags = array_key_exists('flags', $rule) ? $rule['flags'] : 0x00;

		if (($flags & API_ALLOW_NULL) && $data === null) {
			return true;
		}

		if (($flags & API_NORMALIZE) && self::validateUInt64([], $data, '', $e)) {
			$data = [$data];
		}
		unset($e);

		if (!is_array($data)) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('an array is expected'));
			return false;
		}

		if (($flags & API_NOT_EMPTY) && !$data) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('cannot be empty'));
			return false;
		}

		$data = array_values($data);
		$rules = ['type' => API_UINT64];

		foreach ($data as $index => &$value) {
			$subpath = ($path === '/' ? $path : $path.'/').($index + 1);
			if (!self::validateData($rules, $value, $subpath, $error)) {
				return false;
			}
		}
		unset($value);

		return true;
	}

	/**
	 * Floating point number validator.
	 *
	 * @param array  $rule
	 * @param int    $rule['flags']   (optional) API_ALLOW_NULL
	 * @param mixed  $data
	 * @param string $path
	 * @param string $error
	 *
	 * @return bool
	 */
	private static function validateFloat($rule, &$data, $path, &$error) {
		$flags = array_key_exists('flags', $rule) ? $rule['flags'] : 0x00;

		if (($flags & API_ALLOW_NULL) && $data === null) {
			return true;
		}

		if (is_int($data) || is_float($data)) {
			$value = (float) $data;
		}
		elseif (is_string($data)) {
			$number_parser = new CNumberParser();

			if ($number_parser->parse($data) == CParser::PARSE_SUCCESS) {
				$value = (float) $number_parser->getMatch();
			}
			else {
				$value = NAN;
			}
		}
		else {
			$value = NAN;
		}

		if (is_nan($value)) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('a floating point value is expected'));

			return false;
		}

		$data = $value;

		return true;
	}

	/**
	 * Array of floating point numbers validator.
	 *
	 * @param array  $rule
	 * @param int    $rule['flags']   (optional) API_NOT_EMPTY, API_ALLOW_NULL, API_NORMALIZE
	 * @param mixed  $data
	 * @param string $path
	 * @param string $error
	 *
	 * @return bool
	 */
	private static function validateFloats($rule, &$data, $path, &$error) {
		$flags = array_key_exists('flags', $rule) ? $rule['flags'] : 0x00;

		if (($flags & API_ALLOW_NULL) && $data === null) {
			return true;
		}

		if (($flags & API_NORMALIZE) && self::validateFloat([], $data, '', $e)) {
			$data = [$data];
		}
		unset($e);

		if (!is_array($data)) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('an array is expected'));
			return false;
		}

		if (($flags & API_NOT_EMPTY) && !$data) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('cannot be empty'));
			return false;
		}

		$data = array_values($data);
		$rules = ['type' => API_FLOAT];

		foreach ($data as $index => &$value) {
			$subpath = ($path === '/' ? $path : $path.'/').($index + 1);
			if (!self::validateData($rules, $value, $subpath, $error)) {
				return false;
			}
		}
		unset($value);

		return true;
	}

	private static function Int32In($data, $in) {
		$valid = false;

		foreach (explode(',', $in) as $in) {
			if (strpos($in, ':') !== false) {
				list($from, $to) = explode(':', $in);
			}
			else {
				$from = $in;
				$to = $in;
			}

			if ($from <= $data && $data <= $to) {
				$valid = true;
				break;
			}
		}

		return $valid;
	}

	/**
	 * @param array  $rule
	 * @param int    $rule['in']  (optional)
	 * @param int    $data
	 * @param string $path
	 * @param string $error
	 *
	 * @return bool
	 */
	private static function checkInt32In($rule, $data, $path, &$error) {
		if (!array_key_exists('in', $rule)) {
			return true;
		}

		$valid = self::Int32In($data, $rule['in']);

		if (!$valid) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path,
				_s('value must be one of %1$s', str_replace([',', ':'], [', ', '-'], $rule['in']))
			);
		}

		return $valid;
	}

	/**
	 * Array of integers validator.
	 *
	 * @param array  $rule
	 * @param int    $rule['flags']   (optional) API_NOT_EMPTY, API_ALLOW_NULL, API_NORMALIZE
	 * @param string $rule['in']      (optional) a comma-delimited character string, for example: '0,60:900'
	 * @param mixed  $data
	 * @param string $path
	 * @param string $error
	 *
	 * @return bool
	 */
	private static function validateInts32($rule, &$data, $path, &$error) {
		$flags = array_key_exists('flags', $rule) ? $rule['flags'] : 0x00;

		if (($flags & API_ALLOW_NULL) && $data === null) {
			return true;
		}

		if (($flags & API_NORMALIZE) && self::validateInt32([], $data, '', $e)) {
			$data = [$data];
		}
		unset($e);

		if (!is_array($data)) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('an array is expected'));
			return false;
		}

		if (($flags & API_NOT_EMPTY) && !$data) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('cannot be empty'));
			return false;
		}

		$data = array_values($data);
		$rules = ['type' => API_INT32];

		if (array_key_exists('in', $rule)) {
			$rules['in'] = $rule['in'];
		}

		foreach ($data as $index => &$value) {
			$subpath = ($path === '/' ? $path : $path.'/').($index + 1);
			if (!self::validateData($rules, $value, $subpath, $error)) {
				return false;
			}
		}
		unset($value);

		return true;
	}

	/**
	 * Identifier validator.
	 *
	 * @param array  $rule
	 * @param int    $rule['flags']   (optional) API_ALLOW_NULL, API_NOT_EMPTY
	 * @param mixed  $data
	 * @param string $path
	 * @param string $error
	 *
	 * @return bool
	 */
	private static function validateId($rule, &$data, $path, &$error) {
		$flags = array_key_exists('flags', $rule) ? $rule['flags'] : 0x00;

		if (($flags & API_ALLOW_NULL) && $data === null) {
			return true;
		}

		if (!is_scalar($data) || is_bool($data) || is_double($data) || !ctype_digit(strval($data))) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('a number is expected'));
			return false;
		}

		if (($flags & API_NOT_EMPTY) && $data == 0) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('cannot be empty'));
			return false;
		}

		if (bccomp($data, ZBX_DB_MAX_ID) > 0) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('a number is too large'));
			return false;
		}

		$data = (string) $data;

		if ($data[0] === '0') {
			$data = ltrim($data, '0');

			if ($data === '') {
				$data = '0';
			}
		}

		return true;
	}

	/**
	 * Boolean validator.
	 *
	 * @param array  $rule
	 * @param int    $rule['flags']  (optional) API_ALLOW_NULL
	 * @param mixed  $data
	 * @param string $path
	 * @param string $error
	 *
	 * @return bool
	 */
	private static function validateBoolean($rule, &$data, $path, &$error) {
		$flags = array_key_exists('flags', $rule) ? $rule['flags'] : 0x00;

		if (($flags & API_ALLOW_NULL) && $data === null) {
			return true;
		}

		if (!is_bool($data)) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('a boolean is expected'));
			return false;
		}

		return true;
	}

	/**
	 * Flag validator.
	 *
	 * @param array  $rule
	 * @param mixed  $data
	 * @param string $path
	 * @param string $error
	 *
	 * @return bool
	 */
	private static function validateFlag($rule, &$data, $path, &$error) {
		if (is_bool($data)) {
			return true;
		}

		/**
		 * @deprecated  As of version 3.4, use boolean flags only.
		 */
		trigger_error(_('Non-boolean flags are deprecated.'), E_USER_NOTICE);

		$data = !is_null($data);

		return true;
	}

	/**
	 * Object validator.
	 *
	 * @param array  $rul
	 * @param int    $rule['flags']                                   (optional) API_ALLOW_NULL
	 * @param array  $rule['fields']
	 * @param int    $rule['fields'][<field_name>]['flags']           (optional) API_REQUIRED, API_DEPRECATED
	 * @param mixed  $rule['fields'][<field_name>]['default']         (optional)
	 * @param string $rule['fields'][<field_name>]['default_source']  (optional)
	 * @param mixed  $data
	 * @param string $path
	 * @param string $error
	 *
	 * @return bool
	 */
	private static function validateObject($rule, &$data, $path, &$error) {
		$flags = array_key_exists('flags', $rule) ? $rule['flags'] : 0x00;

		if (($flags & API_ALLOW_NULL) && $data === null) {
			return true;
		}

		if (!is_array($data)) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('an array is expected'));
			return false;
		}

		// unexpected parameter validation
		foreach ($data as $field_name => $value) {
			if (!array_key_exists($field_name, $rule['fields'])) {
				$error = _s('Invalid parameter "%1$s": %2$s.', $path, _s('unexpected parameter "%1$s"', $field_name));
				return false;
			}
		}

		// validation of the values type
		foreach ($rule['fields'] as $field_name => $field_rule) {
			$flags = array_key_exists('flags', $field_rule) ? $field_rule['flags'] : 0x00;

			if (array_key_exists('default', $field_rule) && !array_key_exists($field_name, $data)) {
				$data[$field_name] = $field_rule['default'];
			}

			if (array_key_exists('default_source', $field_rule) && !array_key_exists($field_name, $data)) {
				$data[$field_name] = $data[$field_rule['default_source']];
			}

			if (array_key_exists($field_name, $data)) {
				$subpath = ($path === '/' ? $path : $path.'/').$field_name;
				if (!self::validateData($field_rule, $data[$field_name], $subpath, $error, $data)) {
					return false;
				}
				if ($flags & API_DEPRECATED) {
					trigger_error(_s('Parameter "%1$s" is deprecated.', $subpath), E_USER_NOTICE);
				}
			}
			elseif ($flags & API_REQUIRED) {
				$error = _s('Invalid parameter "%1$s": %2$s.', $path,
					_s('the parameter "%1$s" is missing', $field_name)
				);
				return false;
			}
		}

		return true;
	}

	/**
	 * API output validator.
	 *
	 * @param array  $rule
	 * @param int    $rule['flags']   (optional) API_ALLOW_COUNT, API_ALLOW_NULL
	 * @param string $rule['in']      (optional) comma-delimited field names, for example: 'hostid,name'
	 * @param mixed  $data
	 * @param string $path
	 * @param string $error
	 *
	 * @return bool
	 */
	private static function validateOutput($rule, &$data, $path, &$error) {
		$flags = array_key_exists('flags', $rule) ? $rule['flags'] : 0x00;

		if (($flags & API_ALLOW_NULL) && $data === null) {
			return true;
		}

		if (is_array($data)) {
			$rules = ['type' => API_STRINGS_UTF8, 'uniq' => true];

			if (array_key_exists('in', $rule)) {
				$rules['in'] = $rule['in'];
			}

			return self::validateData($rules, $data, $path, $error)
				&& self::validateDataUniqueness($rules, $data, $path, $error);
		}
		elseif (is_string($data)) {
			$in = ($flags & API_ALLOW_COUNT) ? implode(',', [API_OUTPUT_EXTEND, API_OUTPUT_COUNT]) : API_OUTPUT_EXTEND;

			return self::validateData(['type' => API_STRING_UTF8, 'in' => $in], $data, $path, $error);
		}

		$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('an array or a character string is expected'));

		return false;
	}

	/**
	 * PSK key validator.
	 *
	 * @param array  $rule
	 * @param int    $rule['flags']   (optional) API_NOT_EMPTY
	 * @param int    $rule['length']  (optional)
	 * @param mixed  $data
	 * @param string $path
	 * @param string $error
	 *
	 * @return bool
	 */
	private static function validatePSK($rule, &$data, $path, &$error) {
		$flags = array_key_exists('flags', $rule) ? $rule['flags'] : 0x00;

		if (self::checkStringUtf8($flags & API_NOT_EMPTY, $data, $path, $error) === false) {
			return false;
		}

		$mb_len = mb_strlen($data);

		if ($mb_len != 0 && $mb_len < PSK_MIN_LEN) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _s('minimum length is %1$s characters', PSK_MIN_LEN));
			return false;
		}

		if (preg_match('/^([0-9a-f]{2})*$/i', $data) !== 1) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path,
				_('an even number of hexadecimal characters is expected')
			);
			return false;
		}

		if (array_key_exists('length', $rule) && $mb_len > $rule['length']) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('value is too long'));
			return false;
		}

		return true;
	}

	/**
	 * API sort order validator.
	 *
	 * @param array  $rule
	 * @param mixed  $data
	 * @param string $path
	 * @param string $error
	 *
	 * @return bool
	 */
	private static function validateSortOrder($rule, &$data, $path, &$error) {
		$in = ZBX_SORT_UP.','.ZBX_SORT_DOWN;

		if (self::validateStringUtf8(['in' => $in], $data, $path, $e)) {
			return true;
		}

		if (is_string($data)) {
			$error = $e;
			return false;
		}
		unset($e);

		if (!is_array($data)) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('an array or a character string is expected'));
			return false;
		}

		$data = array_values($data);
		$rules = [
			'type' => API_STRING_UTF8,
			'in' => $in
		];

		foreach ($data as $index => &$value) {
			$subpath = ($path === '/' ? $path : $path.'/').($index + 1);
			if (!self::validateData($rules, $value, $subpath, $error)) {
				return false;
			}
		}
		unset($value);

		return true;
	}

	/**
	 * Array of ids validator.
	 *
	 * @param array  $rule
	 * @param int    $rule['flags']   (optional) API_NOT_EMPTY, API_ALLOW_NULL, API_NORMALIZE
	 * @param mixed  $data
	 * @param string $path
	 * @param string $error
	 *
	 * @return bool
	 */
	private static function validateIds($rule, &$data, $path, &$error) {
		$flags = array_key_exists('flags', $rule) ? $rule['flags'] : 0x00;

		if (($flags & API_ALLOW_NULL) && $data === null) {
			return true;
		}

		if (($flags & API_NORMALIZE) && self::validateId([], $data, '', $e)) {
			$data = [$data];
		}
		unset($e);

		if (!is_array($data)) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('an array is expected'));
			return false;
		}

		if (($flags & API_NOT_EMPTY) && !$data) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('cannot be empty'));
			return false;
		}

		$data = array_values($data);

		foreach ($data as $index => &$value) {
			$subpath = ($path === '/' ? $path : $path.'/').($index + 1);
			if (!self::validateId([], $value, $subpath, $error)) {
				return false;
			}
		}
		unset($value);

		return true;
	}

	/**
	 * Array of objects validator.
	 *
	 * @param array  $rule
	 * @param int    $rule['flags']   (optional) API_NOT_EMPTY, API_ALLOW_NULL, API_NORMALIZE, API_PRESERVE_KEYS
	 * @param array  $rule['fields']
	 * @param mixed  $data
	 * @param string $path
	 * @param string $error
	 *
	 * @return bool
	 */
	private static function validateObjects($rule, &$data, $path, &$error) {
		$flags = array_key_exists('flags', $rule) ? $rule['flags'] : 0x00;

		if (($flags & API_ALLOW_NULL) && $data === null) {
			return true;
		}

		if (!is_array($data)) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('an array is expected'));
			return false;
		}

		if (($flags & API_NOT_EMPTY) && !$data) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('cannot be empty'));
			return false;
		}

		if (($flags & API_NORMALIZE) && $data) {
			reset($data);

			if (!is_int(key($data))) {
				$data = [$data];
			}
		}

		if (!($flags & API_PRESERVE_KEYS)) {
			$data = array_values($data);
		}

		foreach ($data as $index => &$value) {
			$subpath = ($path === '/' ? $path : $path.'/').($index + 1);
			if (!self::validateObject(['fields' => $rule['fields']], $value, $subpath, $error)) {
				return false;
			}
		}
		unset($value);

		return true;
	}

	/**
	 * Host group name validator.
	 *
	 * @param array  $rule
	 * @param int    $rule['flags']   (optional) API_REQUIRED_LLD_MACRO
	 * @param int    $rule['length']  (optional)
	 * @param mixed  $data
	 * @param string $path
	 * @param string $error
	 *
	 * @return bool
	 */
	private static function validateHostGroupName($rule, &$data, $path, &$error) {
		if (self::checkStringUtf8(API_NOT_EMPTY, $data, $path, $error) === false) {
			return false;
		}

		if (array_key_exists('length', $rule) && mb_strlen($data) > $rule['length']) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('value is too long'));

			return false;
		}

		$flags = array_key_exists('flags', $rule) ? $rule['flags'] : 0x00;
		$host_group_name_parser = new CHostGroupNameParser(['lldmacros' => ($flags & API_REQUIRED_LLD_MACRO)]);

		if ($host_group_name_parser->parse($data) != CParser::PARSE_SUCCESS) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('invalid host group name'));

			return false;
		}

		if (($flags & API_REQUIRED_LLD_MACRO) && !$host_group_name_parser->getMacros()) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path,
				_('must contain at least one low-level discovery macro')
			);

			return false;
		}

		return true;
	}

	/**
	 * Host name validator.
	 *
	 * @param array  $rule
	 * @param int    $rule['flags']   (optional) API_REQUIRED_LLD_MACRO
	 * @param int    $rule['length']  (optional)
	 * @param mixed  $data
	 * @param string $path
	 * @param string $error
	 *
	 * @return bool
	 */
	private static function validateHostName($rule, &$data, $path, &$error) {
		if (self::checkStringUtf8(API_NOT_EMPTY, $data, $path, $error) === false) {
			return false;
		}

		if (array_key_exists('length', $rule) && mb_strlen($data) > $rule['length']) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('value is too long'));

			return false;
		}

		$flags = array_key_exists('flags', $rule) ? $rule['flags'] : 0x00;
		$host_name_parser = new CHostNameParser(['lldmacros' => ($flags & API_REQUIRED_LLD_MACRO)]);

		// For example, host prototype name MUST contain macros.
		if ($host_name_parser->parse($data) != CParser::PARSE_SUCCESS) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('invalid host name'));

			return false;
		}

		if (($flags & API_REQUIRED_LLD_MACRO) && !$host_name_parser->getMacros()) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path,
				_('must contain at least one low-level discovery macro')
			);

			return false;
		}

		return true;
	}

	/**
	 * Validator for numeric data with optional suffix.
	 * Supported time suffixes: s, m, h, d, w
	 * Supported metric suffixes: K, M, G, T
	 *
	 * @param array  $rule
	 * @param int    $rule['flags']   (optional) API_NOT_EMPTY
	 * @param int    $rule['length']  (optional)
	 * @param mixed  $data
	 * @param string $path
	 * @param string $error
	 *
	 * @return bool
	 */
	private static function validateNumeric($rule, &$data, $path, &$error) {
		global $DB;

		$flags = array_key_exists('flags', $rule) ? $rule['flags'] : 0x00;

		if (is_int($data)) {
			$data = (string) $data;
		}

		if (self::checkStringUtf8($flags & API_NOT_EMPTY, $data, $path, $error) === false) {
			return false;
		}

		if (array_key_exists('length', $rule) && mb_strlen($data) > $rule['length']) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('value is too long'));

			return false;
		}

		if (($flags & API_NOT_EMPTY) == 0 && $data === '') {
			return true;
		}

		$number_parser = new CNumberParser(['with_suffix' => true]);

		if ($number_parser->parse($data) != CParser::PARSE_SUCCESS) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('a number is expected'));

			return false;
		}

		$value = $number_parser->calcValue();

		if ($DB['DOUBLE_IEEE754']) {
			if (abs($value) > ZBX_FLOAT_MAX) {
				$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('a number is too large'));

				return false;
			}
		}
		else {
			if (abs($value) >= 1E+16) {
				$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('a number is too large'));

				return false;
			}
			elseif ($value != round($value, 4)) {
				$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('a number has too many fractional digits'));

				return false;
			}
		}

		// Remove leading zeros.
		$data = preg_replace('/^(-)?(0+)?(\d.*)$/', '${1}${3}', $data);

		// Add leading zero.
		$data = preg_replace('/^(-)?(\..*)$/', '${1}0${2}', $data);

		return true;
	}

	/**
	 * Global script name validator.
	 *
	 * @param array  $rule
	 * @param int    $rule['length']  (optional)
	 * @param mixed  $data
	 * @param string $path
	 * @param string $error
	 *
	 * @return bool
	 */
	private static function validateScriptName($rule, &$data, $path, &$error) {
		if (self::checkStringUtf8(API_NOT_EMPTY, $data, $path, $error) === false) {
			return false;
		}

		if (array_key_exists('length', $rule) && mb_strlen($data) > $rule['length']) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('value is too long'));
			return false;
		}

		$folders = splitPath($data);
		$folders = array_map('trim', $folders);

		// folder1/{empty}/name or folder1/folder2/{empty}
		foreach ($folders as $folder) {
			if ($folder === '') {
				$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('directory or script name cannot be empty'));
				return false;
			}
		}

		return true;
	}

	/**
	 * User macro validator.
	 *
	 * @param array  $rule
	 * @param int    $rule['length']  (optional)
	 * @param mixed  $data
	 * @param string $path
	 * @param string $error
	 *
	 * @return bool
	 */
	private static function validateUserMacro($rule, &$data, $path, &$error) {
		if (self::checkStringUtf8(API_NOT_EMPTY, $data, $path, $error) === false) {
			return false;
		}

		if (array_key_exists('length', $rule) && mb_strlen($data) > $rule['length']) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('value is too long'));
			return false;
		}

		if ((new CUserMacroParser())->parse($data) != CParser::PARSE_SUCCESS) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('a user macro is expected'));
			return false;
		}

		return true;
	}

	/**
	 * LLD macro validator.
	 *
	 * @param array  $rule
	 * @param int    $rule['length']  (optional)
	 * @param mixed  $data
	 * @param string $path
	 * @param string $error
	 *
	 * @return bool
	 */
	private static function validateLLDMacro($rule, &$data, $path, &$error) {
		if (self::checkStringUtf8(API_NOT_EMPTY, $data, $path, $error) === false) {
			return false;
		}

		if (array_key_exists('length', $rule) && mb_strlen($data) > $rule['length']) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('value is too long'));
			return false;
		}

		if ((new CLLDMacroParser())->parse($data) != CParser::PARSE_SUCCESS) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('a low-level discovery macro is expected'));
			return false;
		}

		return true;
	}

	/**
	 * Time period validator like "1-7,00:00-24:00".
	 *
	 * @param array  $rule
	 * @param int    $rule['length']  (optional)
	 * @param mixed  $data
	 * @param string $path
	 * @param string $error
	 *
	 * @return bool
	 */
	private static function validateRangeTime($rule, &$data, $path, &$error) {
		$flags = array_key_exists('flags', $rule) ? $rule['flags'] : 0x00;

		if (self::checkStringUtf8(API_NOT_EMPTY, $data, $path, $error) === false) {
			return false;
		}

		if (array_key_exists('length', $rule) && mb_strlen($data) > $rule['length']) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('value is too long'));
			return false;
		}

		$range_time_parser = new CRangeTimeParser();

		if ($range_time_parser->parse($data) != CParser::PARSE_SUCCESS) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('a time range is expected'));
			return false;
		}

		return true;
	}

	/**
	 * Time period validator like "1-7,00:00-24:00".
	 *
	 * @param array  $rule
	 * @param int    $rule['flags']   (optional) API_ALLOW_USER_MACRO
	 * @param int    $rule['length']  (optional)
	 * @param mixed  $data
	 * @param string $path
	 * @param string $error
	 *
	 * @return bool
	 */
	private static function validateTimePeriod($rule, &$data, $path, &$error) {
		$flags = array_key_exists('flags', $rule) ? $rule['flags'] : 0x00;

		if (self::checkStringUtf8(API_NOT_EMPTY, $data, $path, $error) === false) {
			return false;
		}

		if (array_key_exists('length', $rule) && mb_strlen($data) > $rule['length']) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('value is too long'));
			return false;
		}

		$time_period_parser = new CTimePeriodsParser(['usermacros' => ($flags & API_ALLOW_USER_MACRO)]);

		if ($time_period_parser->parse($data) != CParser::PARSE_SUCCESS) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('a time period is expected'));
			return false;
		}

		return true;
	}

	/**
	 * Regular expression validator.
	 *
	 * @param array  $rule
	 * @param int    $rule['flags']   (optional) API_NOT_EMPTY
	 * @param int    $rule['length']  (optional)
	 * @param mixed  $data
	 * @param string $path
	 * @param string $error
	 *
	 * @return bool
	 */
	private static function validateRegex($rule, &$data, $path, &$error) {
		$flags = array_key_exists('flags', $rule) ? $rule['flags'] : 0x00;

		if (self::checkStringUtf8($flags, $data, $path, $error) === false) {
			return false;
		}

		if (array_key_exists('length', $rule) && mb_strlen($data) > $rule['length']) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('value is too long'));
			return false;
		}

		if ($data !== '' && $data[0] === '@') {
			return true;
		}

		if (@preg_match('/'.str_replace('/', '\/', $data).'/', '') === false) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('invalid regular expression'));
			return false;
		}

		return true;
	}

	/**
	 * Time unit validator like "10", "20s", "30m", "4h", "{$TIME}" etc.
	 *
	 * @param array  $rule
	 * @param int    $rule['length'] (optional)
	 * @param int    $rule['flags']  (optional) API_NOT_EMPTY, API_ALLOW_USER_MACRO, API_ALLOW_LLD_MACRO,
	 *                                          API_TIME_UNIT_WITH_YEAR
	 * @param int    $rule['in']     (optional)
	 * @param mixed  $data
	 * @param string $path
	 * @param string $error
	 *
	 * @return bool
	 */
	private static function validateTimeUnit($rule, &$data, $path, &$error) {
		$flags = array_key_exists('flags', $rule) ? $rule['flags'] : 0x00;

		/*
		 * It's possible to enter seconds as integers, but by default now we look for strings. For example: "30m".
		 * Other rules like emptiness and invalid characters are validated by parsers.
		 */
		if (is_int($data)) {
			$data = (string) $data;
		}

		if (self::checkStringUtf8($flags & API_NOT_EMPTY, $data, $path, $error) === false) {
			return false;
		}

		if (array_key_exists('length', $rule) && mb_strlen($data) > $rule['length']) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('value is too long'));
			return false;
		}

		if (($flags & API_NOT_EMPTY) == 0 && $data === '') {
			return true;
		}

		$simple_interval_parser = new CSimpleIntervalParser([
			'usermacros' => ($flags & API_ALLOW_USER_MACRO),
			'lldmacros' => ($flags & API_ALLOW_LLD_MACRO),
			'negative' => true,
			'with_year' => ($flags & API_TIME_UNIT_WITH_YEAR)
		]);

		if ($simple_interval_parser->parse($data) != CParser::PARSE_SUCCESS) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('a time unit is expected'));
			return false;
		}

		if (($flags & (API_ALLOW_USER_MACRO | API_ALLOW_LLD_MACRO)) && $data[0] === '{') {
			return true;
		}

		$seconds = timeUnitToSeconds($data);

		if ($seconds < ZBX_MIN_INT32 || $seconds > ZBX_MAX_INT32) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('a number is too large'));
			return false;
		}

		return self::checkInt32In($rule, $seconds, $path, $error);
	}

	/**
	 * Array of ids, int32 or strings uniqueness validator.
	 *
	 * @param array  $rule
	 * @param bool   $rule['uniq']    (optional)
	 * @param array  $data
	 * @param string $path
	 * @param string $error
	 *
	 * @return bool
	 */
	private static function validateStringsUniqueness($rule, array $data = null, $path, &$error) {
		// $data can be NULL when API_ALLOW_NULL is set
		if ($data === null) {
			return true;
		}

		if (!array_key_exists('uniq', $rule) || $rule['uniq'] === false) {
			return true;
		}

		$uniq = [];

		foreach ($data as $index => $value) {
			if (array_key_exists($value, $uniq)) {
				$subpath = ($path === '/' ? $path : $path.'/').($index + 1);
				$error = _s('Invalid parameter "%1$s": %2$s.', $subpath,
					_s('value %1$s already exists', '('.$value.')')
				);
				return false;
			}
			$uniq[$value] = true;
		}

		return true;
	}

	/**
	 * Array of objects uniqueness validator.
	 *
	 * @param array  $rule
	 * @param array  $rule['uniq']    (optional) subsets of unique fields ([['hostid', 'name'], [...]])
	 * @param array  $rule['fields']  (optional)
	 * @param array  $data
	 * @param string $path
	 * @param string $error
	 *
	 * @return bool
	 */
	private static function validateObjectsUniqueness($rule, array $data = null, $path, &$error) {
		// $data can be NULL when API_ALLOW_NULL is set
		if ($data === null) {
			return true;
		}

		if (array_key_exists('uniq', $rule)) {
			foreach ($rule['uniq'] as $field_names) {
				$uniq = [];

				foreach ($data as $index => $object) {
					$_uniq = &$uniq;
					$values = [];
					$level = 1;

					foreach ($field_names as $field_name) {
						if (!array_key_exists($field_name, $object)) {
							break;
						}

						$values[] = $object[$field_name];

						if ($level < count($field_names)) {
							if (!array_key_exists($object[$field_name], $_uniq)) {
								$_uniq[$object[$field_name]] = [];
							}

							$_uniq = &$_uniq[$object[$field_name]];
						}
						else {
							if (array_key_exists($object[$field_name], $_uniq)) {
								$subpath = ($path === '/' ? $path : $path.'/').($index + 1);
								$error = _s('Invalid parameter "%1$s": %2$s.', $subpath, _s('value %1$s already exists',
									'('.implode(', ', $field_names).')=('.implode(', ', $values).')'
								));
								return false;
							}

							$_uniq[$object[$field_name]] = true;
						}

						$level++;
					}
				}
			}
		}

		if (array_key_exists('fields', $rule)) {
			foreach ($data as $index => $object) {
				foreach ($rule['fields'] as $field_name => $field_rule) {
					if (array_key_exists($field_name, $object)) {
						$subpath = ($path === '/' ? $path : $path.'/').($index + 1).'/'.$field_name;
						if (!self::validateDataUniqueness($field_rule, $object[$field_name], $subpath, $error)) {
							return false;
						}
					}
				}
			}
		}

		return true;
	}

	/**
	 * HTTP POST validator. Posts can be set to string (raw post) or to http pairs (form fields)
	 *
	 * @param array  $rule
	 * @param int    $rule['length']        (optional)
	 * @param int    $rule['name-length']   (optional)
	 * @param int    $rule['value-length']  (optional)
	 * @param mixed  $data
	 * @param string $path
	 * @param string $error
	 *
	 * @return bool
	 */
	private static function validateHttpPosts($rule, &$data, $path, &$error) {
		if (is_array($data)) {
			$rules = ['type' => API_OBJECTS, 'fields' => [
				'name' =>	['type' => API_STRING_UTF8, 'flags' => API_REQUIRED | API_NOT_EMPTY],
				'value' =>	['type' => API_STRING_UTF8, 'flags' => API_REQUIRED]
			]];

			if (array_key_exists('name-length', $rule)) {
				$rules['fields']['name']['length'] = $rule['name-length'];
			}

			if (array_key_exists('value-length', $rule)) {
				$rules['fields']['value']['length'] = $rule['value-length'];
			}
		}
		else {
			$rules = ['type' => API_STRING_UTF8];

			if (array_key_exists('length', $rule)) {
				$rules['length'] = $rule['length'];
			}
		}

		return self::validateData($rules, $data, $path, $error);
	}

	/**
	 * HTTP variable validator.
	 *
	 * @param array  $rule
	 * @param int    $rule['length']  (optional)
	 * @param mixed  $data
	 * @param string $path
	 * @param string $error
	 *
	 * @return bool
	 */
	private static function validateVariableName($rule, &$data, $path, &$error) {
		if (self::checkStringUtf8(API_NOT_EMPTY, $data, $path, $error) === false) {
			return false;
		}

		if (array_key_exists('length', $rule) && mb_strlen($data) > $rule['length']) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('value is too long'));
			return false;
		}

		if (preg_match('/^{[^{}]+}$/', $data) !== 1) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('is not enclosed in {} or is malformed'));
			return false;
		}

		return true;
	}

	/**
	 * URL validator.
	 *
	 * @param array  $rule
	 * @param int    $rule['length']  (optional)
	 * @param int    $rule['flags']   (optional) API_ALLOW_USER_MACRO, API_ALLOW_EVENT_TAGS_MACRO, API_NOT_EMPTY
	 * @param mixed  $data
	 * @param string $path
	 * @param string $error
	 *
	 * @return bool
	 */
	private static function validateUrl($rule, &$data, $path, &$error) {
		$flags = array_key_exists('flags', $rule) ? $rule['flags'] : 0x00;

		if (self::checkStringUtf8($flags & API_NOT_EMPTY, $data, $path, $error) === false) {
			return false;
		}

		if (array_key_exists('length', $rule) && mb_strlen($data) > $rule['length']) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('value is too long'));
			return false;
		}

		$options = [
			'allow_user_macro' => (bool) ($flags & API_ALLOW_USER_MACRO),
			'allow_event_tags_macro' => (bool) ($flags & API_ALLOW_EVENT_TAGS_MACRO)
		];

		if ($data !== '' && CHtmlUrlValidator::validate($data, $options) === false) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('unacceptable URL'));
			return false;
		}

		return true;
	}

	/**
	 * Trigger expression validator.
	 *
	 * @param array  $rule
	 * @param int    $rule['length']  (optional)
	 * @param int    $rule['flags']   (optional) API_ALLOW_LLD_MACRO, API_NOT_EMPTY
	 * @param mixed  $data
	 * @param string $path
	 * @param string $error
	 *
	 * @return bool
	 */
	private static function validateTriggerExpression($rule, &$data, $path, &$error) {
		$flags = array_key_exists('flags', $rule) ? $rule['flags'] : 0x00;

		if (self::checkStringUtf8($flags & API_NOT_EMPTY, $data, $path, $error) === false) {
			return false;
		}

		if (($flags & API_NOT_EMPTY) == 0 && $data === '') {
			return true;
		}

		if (array_key_exists('length', $rule) && mb_strlen($data) > $rule['length']) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('value is too long'));
			return false;
		}

		$expression_data = new CTriggerExpression([
			'lldmacros' => ($flags & API_ALLOW_LLD_MACRO),
			'lowercase_errors' => true
		]);

		if (!$expression_data->parse($data)) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path, $expression_data->error);
			return false;
		}

		if (!$expression_data->expressions) {
			$error = _s('Invalid parameter "%1$s": %2$s.', $path,
				_('trigger expression must contain at least one host:key reference')
			);
			return false;
		}

		return true;
	}

	/**
	 * JSON RPC parameters validator. Parameters MUST contain an array or object value.
	 *
	 * @param array  $rule
	 * @param mixed  $data
	 * @param string $path
	 * @param string $error
	 *
	 * @return bool
	 */
	private static function validateJsonRpcParams($rule, &$data, $path, &$error) {
		if (is_array($data)) {
			return true;
		}

		$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('an array or object is expected'));

		return false;
	}

	/**
	 * JSON RPC identifier validator. This identifier MUST contain a String, Number, or NULL value.
	 *
	 * @param array  $rule
	 * @param mixed  $data
	 * @param string $path
	 * @param string $error
	 *
	 * @return bool
	 */
	private static function validateJsonRpcId($rule, &$data, $path, &$error) {
		if (is_string($data) || is_int($data) || is_float($data) || $data === null) {
			return true;
		}

		$error = _s('Invalid parameter "%1$s": %2$s.', $path, _('a string, number or null value is expected'));

		return false;
	}
}