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SassMeister-input.scss

// ----
// libsass (v3.2.4)
// ----

// https://github.com/ericam/true
@import "true";

$color-stack:
  (group: orange, shade: normal, color: #e67835),
  (group: orange, shade: pale,   color: #f8a878),
  (group: orange, shade: dark,   color: #ad490c),
  (group: blue,   shade: normal, color: #426682);
  

// Color  Function
@function color($group, $shade:normal, $transparency:1, $color:null){
  $_return: null;
  $_color: null;

  @each $c-color in $color-stack {
    @if (type-of($c-color) == map) {
      $c-group: map-get($c-color, group);
      $c-shade: map-get($c-color, shade);
      @if ($group == map-get($c-color, group) and $shade == map-get($c-color, shade) and $_color == null) {
        $_color: map-get($c-color, color);
      }
    }
  }
  
  // If color was passed in
  @if ($color != null) {
    
    // If color was found
    @if ($_color != null) {
      
      // If colors don't match
      @if ($_color != $color) {
        @error "Found different color (#{$_color}) than color passed in (#{$color}) for given group (#{$group}) and shade (#{$shade})";
      }
    }
    
    // No color was found
    @else {
      // See if color is defined but for different group and shade
      $c-color: _color_stack_entry($color);
      
      @if ($c-color != null) {
        @error "Found color (#{$color}) already defined for different group (#{map-get($c-color, group)}) and shade (#{map-get($c-color, shade)}) than passed in group (#{$group}) and shade (#{$shade})";
      }

      // Add the new color
      $c-color: (group: $group, shade: $shade, color: $color);
      $color-stack: append($color-stack, $c-color, comma) !global;
      $_color: $color;
    }
  }
  
  @if ($_color == null) {
    @error "No color found for given group (#{$group}) and shade (#{$shade})";
  }
  
  @return rgba($_color, $transparency);
}

// See if a color is already defined in our color stack
@function _color_stack_entry($color) {
  $_return: null;
  
  @each $cse in $color-stack {
    @if ($_return == null) {
      @if ($color == map-get($cse, color)) {
        $_return: (group: map-get($cse, group), shade: map-get($cse, shade), color: $color);
      }
    }
  }
  
  @return $_return;
}

@include test-module('Utilities') {
  @include test('Color [function]') {
    $test: color(orange, normal, 1);
    $expect: rgba(#e67835, 1);
    @include assert-equal($test, $expect, 'Found color in stack');
    
    $test: color(black, normal, 1, #000);
    $expect: rgba(#000, 1);
    @include assert-equal($test, $expect, 'Added color to stack');
    
    $test: color(black, normal, 1);
    $expect: rgba(#000, 1);
    @include assert-equal($test, $expect, 'Found added color in stack');
  }
  
  @include test('Color Stack Entry [function]') {
    $test: _color_stack_entry(#fff);
    $expect: null;
    @include assert-equal($test, $expect, 'Unfound color returns null');
    
    $test: _color_stack_entry(#ad490c);
    $expect: (group: orange, shade: dark, color: #ad490c);
    @include assert_equal($test, $expect, 'Found color return color stack entry');
  }
}