@function __trimmed-left-index($string) {
    $index: 1;
    $length: str-length($string);

    @while ($index <= $length) and (__is-space(__char-at($string, $index))) {
        $index: $index + 1;
    }

    @return $index;
}


@function __trimmed-right-index($string) {
    $index: str-length($string);

    @while ($index > 0) and (__is-space(__char-at($string, $index))) {
        $index: $index - 1;
    }

    @return $index;
}


@function __trim($string, $chars: null, $guard: null) {
    $value: $string;
    $string: __base-to-string($string);

    @if not ($string) or ($string == '') or ($chars == '') {
        @return $string;
    }

    @if (if($guard, __is-iteratee-call($value, $chars, $guard), ($chars == null))) {
        @return str-slice($string, __trimmed-left-index($string), __trimmed-right-index($string));
    }

    $chars: __base-to-string($chars);

    @return str-slice($string,
        __chars-left-index($string, $chars),
        __chars-right-index($string, $chars));
}


@function __trim-left($string, $chars: null, $guard: null) {
    $value: $string;
    $string: __base-to-string($string);

    @if not ($string) or ($string == '') or ($chars == '') {
        @return $string;
    }

    @if (if($guard, __is-iteratee-call($value, $chars, $guard), ($chars == null))) {
        @return str-slice($string, __trimmed-left-index($string));
    }

    $chars: __base-to-string($chars);

    @return str-slice($string,
        __chars-left-index($string, $chars));
}


@function __trim-right($string, $chars: null, $guard: null) {
    $value: $string;
    $string: __base-to-string($string);

    @if not ($string) or ($string == '') or ($chars == '') {
        @return $string;
    }

    @if (if($guard, __is-iteratee-call($value, $chars, $guard), ($chars == null))) {
        @return str-slice($string, 0, __trimmed-right-index($string));
    }

    $chars: __base-to-string($chars);

    @return str-slice($string, 0,
        __chars-right-index($string, $chars));
}


/// Removes leading and trailing whitespace or specified characters from `$string`.
///
///
/// @access public
/// @group String
/// @param {string} $string [''] - The string to trim.
/// @param {string} $chars [' '] - The characters to trim.
/// @returns {string} Returns the trimmed string.
/// @example scss
/// $foo: _trim('  abc  ');
/// // => 'abc'
/// $foo: _trim('-_-abc-_-', '_-');
/// // => 'abc'
/// $foo: _map(('  foo  ', '  bar  '), _trim);
/// // => ('foo', 'bar')

@function _trim($args...) {
    @return call(get-function('__trim'), $args...);
}


/// Removes leading whitespace or specified characters from `$string`.
///
///
/// @access public
/// @group String
/// @param {string} $string [''] - The string to trim.
/// @param {string} $chars [whitespace] - The characters to trim.
/// @returns {string} Returns the trimmed string.
/// @example scss
/// /// _trim-left('  abc  ');
/// // => 'abc  '
/// /// _trim-left('-_-abc-_-', '_-');
/// // => 'abc-_-'

@function _trim-left($args...) {
    @return call(get-function('__trim-left'), $args...);
}


/// Removes trailing whitespace or specified characters from `$string`.
///
///
/// @access public
/// @group String
/// @param {string} $string [''] - The string to trim.
/// @param {string} $chars [' '] - The characters to trim.
/// @returns {string} Returns the trimmed string.
/// @example scss
/// $foo: _trim-right('  abc  ');
/// // => '  abc'
/// $foo: _trim-right('-_-abc-_-', '_-');
/// // => '-_-abc'

@function _trim-right($args...) {
    @return call(get-function('__trim-right'), $args...);
}