// Copyright (c) roydukkey. All rights reserved.
// Licensed under the MIT. See LICENSE file in the project root for full license information.
// Copyright (c) 2017 Alex Page. Licensed under the MIT. Sourced and Modified 2021.

@use 'sass:color'
@use 'sass:map'
@use 'sass:math'
@use 'sass:meta'
@use 'sass:string'
@use '@sass-fairy/exception/src/parameter'
@use '@sass-fairy/exception/src/parameter-type'
@use 'contrast'


///
/// @throw `#{$a11y-color|$other-color}` is not a color.
/// @throw Must be either "normal" or "large".
/// @throw Must be either "AA" or "AAA".
///
@function a11y($a11y-color, $other-color, $size: 'normal', $level: 'AA')

	@if meta.type-of($a11y-color) != 'color'
		@error parameter-type.parameter-type('a11y', 'a11y-color', $a11y-color, 'color')

	@if meta.type-of($other-color) != 'color'
		@error parameter-type.parameter-type('a11y', 'other-color', $other-color, 'color')

	@if meta.type-of($size) == 'string'
		$size: string.to-lower-case($size)

	@if $size != 'normal' and $size != 'large'
		@error parameter.parameter('Must be either "normal" or "large"', 'a11y', 'size')

	@if meta.type-of($level) == 'string'
		$level: string.to-upper-case($level)

	@if $level != 'AA' and $level != 'AAA'
		@error parameter.parameter('Must be either "AA" or "AAA"', 'a11y', 'level')

	$size: map.get(contrast.$contrast-ratios, $level, $size)

	@if contrast.contrast($a11y-color, $other-color) >= $size
		@return $a11y-color

	$lightness: color.channel($a11y-color, 'lightness', $space: hsl)

	$is-contrasted-to-black: contrast.contrast(#000, $other-color) >= $size
	$is-contrasted-to-white: contrast.contrast(#fff, $other-color) >= $size
	$min-lightness: 0
	$max-lightness: 100
	$is-dark: false

	@if $is-contrasted-to-black and $is-contrasted-to-white

		@if $lightness >= 50
			$min-lightness: $lightness

		@else
			$max-lightness: $lightness
			$is-dark: true

	@else if $is-contrasted-to-black
		$max-lightness: $lightness
		$is-dark: true

	@else
		$min-lightness: $lightness

	$found-color: null

	@while $found-color == null
		$mid-lightness: math.div($min-lightness + $max-lightness, 2)
		$mid-color: hsl(color.channel($a11y-color, 'hue', $space: hsl), color.channel($a11y-color, 'saturation', $space: hsl), $mid-lightness)

		@if contrast.contrast($mid-color, $other-color) >= $size
			@if	$max-lightness - $min-lightness < math.div(100, 255)
				$found-color: $mid-color

			@if $is-dark
				$min-lightness: $mid-lightness

			@else
				$max-lightness: $mid-lightness

		@else if $is-dark
			$max-lightness: $mid-lightness

		@else
			$min-lightness: $mid-lightness

	@return $found-color