@function __encode-uri-char($char, $args...) {
  $char-code: _char-code($char);

  @if not $char-code {
    @return $char;
  }

  @if (($char-code >= 48 and $char-code <= 57)
    or ($char-code >= 65 and $char-code <= 90)
    or ($char-code >= 97 and $char-code <= 122)) {
    @return $char;
  }

  @return unquote("%#{str-slice(ie-hex-str(rgb($char-code,0,0)),4,5)}");
}


@function __encode($string, $args...) {
  @return _($string,
    _map __encode-uri-char,
    _join);
}


/// Converts a `$string` to a URL encoding representation by converting
/// certain characters to their 2-digit hexadecimal equivalent,
/// preceded by a "%" sign.
/// 
/// @access public
/// @group String
/// @param {String} $string The string to encode.
/// @returns {String} Returns the encoded string.
/// 
/// @example scss
/// $foo: _encode('Hello world');
/// // => 'Hello%20world'

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