thoughtbot/bourbon

@charset "UTF-8";

/// Programatically determines the contrast ratio between two colors.
///
/// Note that the alpha channel is ignored.
///
/// @link https://goo.gl/54htLV
///
/// @argument {color (hex)} $color-1
///
/// @argument {color (hex)} $color-2
///
/// @return {number (1-21)}
///
/// @example scss
///   _contrast-ratio(black, white)
///
/// @require {function} _lightness
///
/// @access private

@use "sass:math";

@function _contrast-ratio($color-1, $color-2) {
  $-local-lightness-1: _lightness($color-1) + 0.05;
  $-local-lightness-2: _lightness($color-2) + 0.05;

  @if $-local-lightness-1 > $-local-lightness-2 {
    @return math.div($-local-lightness-1, $-local-lightness-2);
  } @else {
    @return math.div($-local-lightness-2, $-local-lightness-1);
  }
}