// Utilities
// =========


// Get Function
// ------------
/// Get a first-class function in Sass 3.5+,
/// or the function name string (unchanged)
/// in older Sass versions.
/// This is safe to use internally,
/// as it allows users to pass in
/// either a string, or a previously-captured function.
/// Users can also add captured functions
/// to the provided `$functions` map
/// in order to call them by name.
///
/// @access private
/// @see $functions
///
/// @param {string | function} $function -
///   The name (string) of a function,
///   or the function to be called.
/// @return {string | function} -
///   Returns a first-class function in Sass 3.5+,
///   or the function name string in older Sass versions.
@function _ac-scale-get-function(
  $function
) {
  $type: type-of($function);

  @if ($type == 'function') {
    @return $function;
  }

  @if function-exists('get-function') {
    @if index($_LOCAL-SCALE-FUNCTIONS, $function) {
      @return get-function($function);
    }

    @if map-has-key($functions, $function) {
      $function: map-get($functions, $function);
      @return _ac-scale-get-function($function);
    }

    @error '[#{$type}] `#{$function}` must be a first-class function';
  }

  @return $function;
}


// Format String
// -------------
/// Define your own format-string
/// for building `calc(%s + %s) ('root', 'rhythm')` recipies.
///
/// @group config
/// @type string
///
/// @example scss -
///   $ac-format-string: '@@@';
$ac-format-string: '%s';


// String Replace
// --------------
/// Return a string, with a substring replaced
///
/// @access private
///
/// @param {string} $string -
///   The original string to be edited
/// @param {string} $old -
///   A sub-string to replace
/// @param {string} $new -
///   A new sub-string to replace the old
/// @return {string} -
///   Original string, with substring replaced
@function _ac-str-replace(
  $string,
  $old,
  $new: null,
  $replace-all: false
) {
  $return: $string;
  $i: str-index($string, $old);
  $n: str-length($old);

  @if $string == $old {
    $return: $new;
  } @else if $i {
    $a: if($i > 1, str-slice($string, 1, $i - 1), '');
    $z: str-slice($string, $i + $n);

    @if $replace-all {
      $z: _ac-str-replace($z, $old, $new, true);
    }

    $return: $a + if($new, $new, '') + $z;
  }

  @return $return;
}


// Interpolate
// -----------
/// Return a string with interpolated values
/// replacing `%s` format strings
///
/// @access private
///
/// @param {string} $string -
///   The original string to be edited
/// @param {strings} $values... -
///   New strings, to replace the `%s` format strings
/// @return {string} -
///   Original string, with `%s` format strings replaced
@function _ac-interpolate(
  $string,
  $values...
) {
  $_return: $string;

  @each $val in $values {
    @if str-index($_return, $ac-format-string) {
      $_return: _ac-str-replace($_return, $ac-format-string, $val);
    } @else {
      @warn 'Too many values passed for interpolation with "#{$string}".';
    }
  }

  @return $_return;
}