////
/// @group theme
////

@import './color-palette';

/// This is the default contrast ratio to use for color accessibility between
/// background and foreground colors. This number should be at least:
/// - 3 for large text (18pt normal or 14pt bold)
/// - 4.5 for normal text
/// - 7.1 for Level AAA requirements.
///
/// @link https://www.w3.org/TR/WCAG20/#visual-audio-contrast-contrast
/// @type Number
$rmd-theme-default-contrast-ratio: 3 !default;

/// Precomputed linear color channel values, for use in contrast calculations.
/// See https://www.w3.org/TR/WCAG20-TECHS/G17.html#G17-tests
///
/// Algorithm, for c in 0 to 255:
/// f(c) {
///   c = c / 255;
///   return c < 0.03928 ? c / 12.92 : Math.pow((c + 0.055) / 1.055, 2.4);
/// }
///
/// This lookup table is needed since there is no `pow` in SCSS/Sass. You _can_
/// make your own, but it is recommended to pass the computed values from a
/// 'more complete' layer (like node) as a lookup table to speed up compilation
/// time.
/// @access private
/// @type List
$rmd-theme-linear-channel-values: (
  0 0.0003035269835488375 0.000607053967097675 0.0009105809506465125 0.00121410793419535
    0.0015176349177441874 0.001821161901293025 0.0021246888848418626 0.0024282158683907
    0.0027317428519395373 0.003035269835488375 0.003346535763899161 0.003676507324047436
    0.004024717018496307 0.004391442037410293 0.004776953480693729 0.005181516702338386
    0.005605391624202723 0.006048833022857054 0.006512090792594475 0.006995410187265387
    0.007499032043226175 0.008023192985384994 0.008568125618069307 0.009134058702220787
    0.00972121732023785 0.010329823029626936 0.010960094006488246 0.011612245179743885
    0.012286488356915872 0.012983032342173012 0.013702083047289686 0.014443843596092545
    0.01520851442291271 0.01599629336550963 0.016807375752887384 0.017641954488384078
    0.018500220128379697 0.019382360956935723 0.0202885630566524 0.021219010376003555
    0.022173884793387385 0.02315336617811041 0.024157632448504756 0.02518685962736163
    0.026241221894849898 0.027320891639074894 0.028426039504420793 0.0295568344378088
    0.030713443732993635 0.03189603307301153 0.033104766570885055 0.03433980680868217
    0.03560131487502034 0.03688945040110004 0.0382043715953465 0.03954623527673284
    0.04091519690685319 0.042311410620809675 0.043735029256973465 0.04518620438567554
    0.046665086336880095 0.04817182422688942 0.04970656598412723 0.05126945837404324
    0.052860647023180246 0.05448027644244237 0.05612849004960009 0.05780543019106723
    0.0595112381629812 0.06124605423161761 0.06301001765316767 0.06480326669290577
    0.06662593864377289 0.06847816984440017 0.07036009569659588 0.07227185068231748
    0.07421356838014963 0.07618538148130785 0.07818742180518633 0.08021982031446832
    0.0822827071298148 0.08437621154414882 0.08650046203654976 0.08865558628577294
    0.09084171118340768 0.09305896284668745 0.0953074666309647 0.09758734714186246
    0.09989872824711389 0.10224173308810132 0.10461648409110419 0.10702310297826761
    0.10946171077829933 0.1119324278369056 0.11443537382697373 0.11697066775851084
    0.11953842798834562 0.12213877222960187 0.12477181756095049 0.12743768043564743
    0.1301364766903643 0.13286832155381798 0.13563332965520566 0.13843161503245183
    0.14126329114027164 0.14412847085805777 0.14702726649759498 0.14995978981060856
    0.15292615199615017 0.1559264637078274 0.1589608350608804 0.162029375639111 0.1651321945016676
    0.16826940018969075 0.1714411007328226 0.17464740365558504 0.17788841598362912
    0.18116424424986022 0.184474994500441 0.18782077230067787 0.19120168274079138 0.1946178304415758
    0.19806931955994886 0.20155625379439707 0.20507873639031693 0.20863687014525575
    0.21223075741405523 0.21586050011389926 0.2195261997292692 0.2232279573168085
    0.22696587351009836 0.23074004852434915 0.23455058216100522 0.238397573812271
    0.24228112246555486 0.24620132670783548 0.25015828472995344 0.25415209433082675
    0.2581828529215958 0.26225065752969623 0.26635560480286247 0.2704977910130658
    0.27467731206038465 0.2788942634768104 0.2831487404299921 0.2874408377269175 0.29177064981753587
    0.2961382707983211 0.3005437944157765 0.3049873140698863 0.30946892281750854 0.31398871337571754
    0.31854677812509186 0.32314320911295075 0.3277780980565422 0.33245153634617935
    0.33716361504833037 0.3419144249086609 0.3467040563550296 0.35153259950043936 0.3564001441459435
    0.3613067797835095 0.3662525955988395 0.3712376804741491 0.3762621229909065 0.38132601143253014
    0.386429433787049 0.39157247774972326 0.39675523072562685 0.4019777798321958 0.4072402119017367
    0.41254261348390375 0.4178850708481375 0.4232676699860717 0.4286904966139066 0.43415363617474895
    0.4396571738409188 0.44520119451622786 0.45078578283822346 0.45641102318040466
    0.4620769996544071 0.467783796112159 0.47353149614800955 0.4793201831008268 0.4851499400560704
    0.4910208498478356 0.4969329950608704 0.5028864580325687 0.5088813208549338 0.5149176653765214
    0.5209955732043543 0.5271151257058131 0.5332764040105052 0.5394794890121072 0.5457244613701866
    0.5520114015120001 0.5583403896342679 0.5647115057049292 0.5711248294648731 0.5775804404296506
    0.5840784178911641 0.5906188409193369 0.5972017883637634 0.6038273388553378 0.6104955708078648
    0.6172065624196511 0.6239603916750761 0.6307571363461468 0.6375968739940326 0.6444796819705821
    0.6514056374198242 0.6583748172794485 0.665387298282272 0.6724431569576875 0.6795424696330938
    0.6866853124353135 0.6938717612919899 0.7011018919329731 0.7083757798916868 0.7156935005064807
    0.7230551289219693 0.7304607400903537 0.7379104087727308 0.7454042095403874 0.7529422167760779
    0.7605245046752924 0.768151147247507 0.7758222183174236 0.7835377915261935 0.7912979403326302
    0.799102738014409 0.8069522576692516 0.8148465722161012 0.8227857543962835 0.8307698767746546
    0.83879901174074 0.846873231509858 0.8549926081242338 0.8631572134541023 0.8713671191987972
    0.8796223968878317 0.8879231178819663 0.8962693533742664 0.9046611743911496 0.9130986517934192
    0.9215818562772946 0.9301108583754237 0.938685728457888 0.9473065367331999 0.9559733532492861
    0.9646862478944651 0.9734452903984125 0.9822505503331171 0.9911020971138298 1
);

/// Calculate the luminance for a color.
///
/// @access private
/// @link https://www.w3.org/TR/WCAG20-TECHS/G17.html#G17-tests
/// @param {Color} color - The color to check
/// @returns {Number} A number representing the luminance for the color.
@function rmd-theme-luminance($color) {
  $red: nth($rmd-theme-linear-channel-values, red($color) + 1);
  $red-multiplier: 0.2126;
  $green: nth($rmd-theme-linear-channel-values, green($color) + 1);
  $green-multiplier: 0.7152;
  $blue: nth($rmd-theme-linear-channel-values, blue($color) + 1);
  $blue-multiplier: 0.0722;

  @return ($red * $red-multiplier) + ($green * $green-multiplier) + ($blue * $blue-multiplier);
}

/// Gets the contrast between two colors.
///
/// @access private
/// @param {Color} back - The background color
/// @param {Color} front - The foreground color that should be compared to
/// the background color for contrast ratio.
/// @returns {Number} The contrast ratio between the background and foreground colors
@function rmd-theme-contrast($back, $front) {
  $back-luminance: rmd-theme-luminance($back) + 0.05;
  $front-luminance: rmd-theme-luminance($front) + 0.05;

  @return max($back-luminance, $front-luminance) / min($back-luminance, $front-luminance);
}

/// Determines if a provided color is considered light or dark.
///
/// @param {Color} color - The color to test.
/// @param {Number} min-contrast [$rmd-theme-default-contrast-ratio] - The
/// minimum contrast that should be applied. The min contrast for normal text
/// should be 4.5 while large or 14px bold text should be 3.1. See the link for
/// contrasts for more information.
/// @returns {String} - The string 'light' if the color is considered light, otherwise 'dark'.
/// @link https://www.w3.org/TR/WCAG20/#visual-audio-contrast-contrast
@function rmd-theme-tone($color, $min-contrast: $rmd-theme-default-contrast-ratio) {
  @if $color == 'dark' or $color == 'light' {
    @return $color;
  }

  $light-contrast: rmd-theme-contrast($color, $rmd-white-base);
  $dark-contrast: rmd-theme-contrast($color, rgba($rmd-black-base, 0.87));

  @if ($light-contrast < $min-contrast) and ($dark-contrast > $light-contrast) {
    @return 'light';
  } @else {
    @return 'dark';
  }
}

/// Determines if the provided color should have a light or dark contrast using
/// the luminance algorithm to maintain a required contrast ratio for
/// accessibility.
///
/// @param {Color} color - The color to test.
/// @param {Number} min-contrast [$rmd-theme-default-contrast-ratio] - The
/// minimum contrast that should be applied. The min contrast for normal text
/// should be 4.5 while large or 14px bold text should be 3.1. See the link for
/// contrasts for more information.
/// @returns {String} - The string 'dark' if the color is considered light, or
/// 'light' if the color is considered dark.
/// @link https://www.w3.org/TR/WCAG20/#visual-audio-contrast-contrast
@function rmd-theme-contrast-tone($color, $min-contrast: $rmd-theme-default-contrast-ratio) {
  @return if(rmd-theme-tone($color) == 'dark', 'light', 'dark');
}