////
/// @author Giana Blantin
////

/// Tries to fix contrast by adjusting $color1
/// @link https://www.w3.org/TR/2016/NOTE-WCAG20-TECHS-20161007/G18#G18-procedure
/// @since 1.12.0 - The Sith
/// @param {Color} $color1 - 1st color to test the contrast against
/// @param {Color} $color2 ["$body-color"] - 2nd color to test the contrast against
/// @param {String | Number} $min-ratio ["AA"] - minimum ratio to test against. Accepted values for this ratio argument are AA and AAALG (4.5:1), AALG (3:1) and AAA (7:1) or a number between 1 and 21.
/// @param {Number} $iterations ["5"] - number of iterations to figure out contrast
/// @return {Color} - a modified color
/// @example scss
///   // using a number as `$min-ratio`
///   fix-color(#00bdd1, #005da3, 3.75)
///   // #00d4ea
///
///   // using a keyword as `$min-ratio`
///   fix-color(#3f464a, #678d7e, AAA)
///   // #000
///
///   // usage
///   .image-caption {
///     color: fix-color(blue, gray);
///   }
@function fix-color($color1, $color2, $min-ratio: "AA", $iterations: 5) {
	// Accept keywords for ratio
	@if ($min-ratio == "AA" or $min-ratio == "AAALG") {
		$min-ratio: 4.5;
	}
	@elseif ($min-ratio == "AALG") {
		$min-ratio: 3;
	}
	@elseif ($min-ratio == "AAA") {
		$min-ratio: 7;
	}

	// If check fails, begin conversion
	@if (not check-contrast($color1, $color2, $min-ratio)) {
		// First get both luminances and clip so #fff and #000 don't break anything
		$lum1: clip(luminance($color1));
		$lum2: clip(luminance($color2));

		// Defaults we'll set later
		$target-luminance: $lum1;
		$operation: "";

		// If the same luminance is passed, lighten/darken one to make conversion possible
		@if ($lum1 == $lum2) {
			// Darken light colors and lighten dark colors, so we have more room to scale them (eg, we won't hit #fff or #000 before we can fix them)
			@if ($lum1 > .5) {
				$color1: darken($color1, 1%);
				$lum1: luminance($color1);
			} @else {
				$color1: lighten($color1, 1%);
				$lum1: luminance($color1);
			}
		}

		// Now let's get the target luminance. This basically reverses check-contrast(), so we know what luminance to aim for
		@if (max($lum1, $lum2) == $lum1) {
			$target-luminance: (($lum2 + .05) * $min-ratio - .05);
			$operation: lighten;
		} @else {
			$target-luminance: (($lum2 + .05) / $min-ratio - .05);
			$operation: darken;
		}

		// Skip the whole conversion if we just need #fff or #000
		@if ($target-luminance >= 1) {
			@return rgb(255, 255, 255);
		}
		@elseif ($target-luminance <= 0) {
			@return rgb(0, 0, 0);
		} @else {
			// Scale color by calculated difference to arrive at target luminance
			$color1: scale-luminance($color1, $target-luminance);

			// Try to fix any rounding errors by lightening or darkening
			$color1: scale-light($color1, $color2, $min-ratio, $operation, $iterations);
		}
	}

	// Tada
	@return $color1;
}