/// Map 对象合并
/// Credit: https://www.sitepoint.com/extra-map-functions-sass/
/// @param {Map} $map - first map
/// @param {ArgList} $maps - other maps
/// @param {Bool} $deep - recursive mode
/// @return {Map} 合并后的 map
@function map-extend($map, $maps... /*, $deep */) {
  $last: nth($maps, -1);
  $deep: $last == true;
  $max: if($deep, length($maps) - 1, length($maps));

  // Loop through all maps in $maps...
  @for $i from 1 through $max {
    // Store current map
    $current: nth($maps, $i);

    // If not in deep mode, simply merge current map with map
    @if not $deep {
      $map: map-merge($map, $current);
    } @else {
      // If in deep mode, loop through all tuples in current map
      /* stylelint-disable-next-line */
      @each $key, $value in $current {
        // If value is a nested map and same key from map is a nested map as well
        /* stylelint-disable-next-line */
        @if type-of($value) == 'map' and type-of(map-get($map, $key)) == 'map' {
          // Recursive extend
          $value: map-extend(map-get($map, $key), $value, true);
        }

        // Merge current tuple with map
        $map: map-merge(
          $map,
          (
            $key: $value
          )
        );
      }
    }
  }

  @return $map;
}

/// 深度合并
@function map-deep-merge($maps...) {
  @return map-extend(append($maps, true));
}

// get top/right/bottom/left value from a shorthand value of
// CSS property like margin/border-width/padding etc...
// @param {List} $shorthand - shorthand value, eg. 10px 20px
// @param {String} $side - side of the box, eg. left
// @return {String} - value of the specified side
@function get-side($shorthand, $side) {
  $length: length($shorthand);

  @if $length == 1 {
    @return $shorthand;
  }

  @if $length == 2 {
    @return map-get(
      (
        top: nth($shorthand, 1),
        right: nth($shorthand, 2),
        bottom: nth($shorthand, 1),
        left: nth($shorthand, 2)
      ),
      $side
    );
  }

  @if $length == 3 {
    @return map-get(
      (
        top: nth($shorthand, 1),
        right: nth($shorthand, 2),
        bottom: nth($shorthand, 3),
        left: nth($shorthand, 2)
      ),
      $side
    );
  }

  @if $length == 4 {
    @return map-get(
      (
        top: nth($shorthand, 1),
        right: nth($shorthand, 2),
        bottom: nth($shorthand, 3),
        left: nth($shorthand, 4)
      ),
      $side
    );
  }
}