SASS Border Shorthand Mixin

border.sass

// Border Shorthand
// -------------------------
=border($border: false, $border_horizontal: false, $border_bottom: false, $border_left: false)
  $args: length($border)

  // Reset Variables Based on Argument Count
  @if $args > 1 and length(nth($border,1)) > 1 or nth($border,1) == none

    @if $args == 4
      $border_left: nth($border, 4)
      $border_bottom: nth($border, 3)
      $border_horizontal: nth($border, 2)
      $border: nth($border, 1)
    @else if $args == 3
      $border_bottom: nth($border, 3)
      $border_horizontal: nth($border, 2)
      $border: nth($border, 1)
    @else if $args == 2
      $border_horizontal: nth($border, 2)
      $border: nth($border, 1)

  // Assign Attributes from Variables
  @if $border and $border_horizontal and $border_bottom and $border_left
    border-top: $border
    border-right: $border_horizontal
    border-bottom: $border_bottom
    border-left: $border_left
  @else if $border and $border_horizontal and $border_bottom
    border: $border_horizontal
    border-top: $border
    border-bottom: $border_bottom
  @else if $border and $border_horizontal
    border: $border
    border-right: $border_horizontal
    border-left: $border_horizontal
  @else
    border: $border