gnerate-border.scss

@mixin generate-border($width, $color, $position: all) {
  $shadows: ();

  @if $position == all {
    $shadows: append($shadows, inset 0 0 0 #{$width} #{$color});
  } @else {
    @each $dir in top, right, bottom, left {
      @if index($position, $dir) {
        $x: 0;
        $y: 0;
        @if $dir == top {
          $y: $width;
        } @else if $dir == right {
          $x: -$width;
        } @else if $dir == bottom {
          $y: -$width;
        } @else if $dir == left {
          $x: $width;
        }

        $shadows: append($shadows, inset #{$x} #{$y} 0 0 #{$color}, comma);
      }
    }
  }

  box-shadow: $shadows;
}