//
// Copyright 2017 Google Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
//

@use "sass:color";
@use "sass:list";
@use "sass:map";
@use "sass:math";
@use "sass:meta";
@use "sass:string";
@use "./constants";

// Calculate the luminance for a color.
// See https://www.w3.org/TR/WCAG20-TECHS/G17.html#G17-tests
@function luminance($color) {
  $red: list.nth(constants.$linear-channel-values, color.red($color) + 1);
  $green: list.nth(constants.$linear-channel-values, color.green($color) + 1);
  $blue: list.nth(constants.$linear-channel-values, color.blue($color) + 1);

  @return .2126 * $red + .7152 * $green + .0722 * $blue;
}

// Calculate the contrast ratio between two colors.
// See https://www.w3.org/TR/WCAG20-TECHS/G17.html#G17-tests
@function contrast($back, $front) {
  $backLum: luminance($back) + .05;
  $foreLum: luminance($front) + .05;

  @return math.max($backLum, $foreLum) / math.min($backLum, $foreLum);
}

// Determine whether the color is "light" or "dark".
@function tone($color) {
  @if $color == "dark" or $color == "light" {
    @return $color;
  }

  $minimumContrast: 3.1;

  $lightContrast: contrast($color, white);
  $darkContrast: contrast($color, rgba(black, .87));

  @if ($lightContrast < $minimumContrast) and ($darkContrast > $lightContrast) {
    @return "light";
  } @else {
    @return "dark";
  }
}

// Determine whether to use dark or light text on top of given color to meet accessibility standards for contrast.
// Returns "dark" if the given color is light and "light" if the given color is dark.
@function contrast-tone($color) {
  @return if(tone($color) == "dark", "light", "dark");
}

@function is-var-with-fallback_($style) {
  @return meta.type-of($style) == "map" and map.has-key($style, "varname") and map.has-key($style, "fallback");
}

@function get-var-fallback_($style) {
  $fallback: map.get($style, "fallback");
  @if is-var-with-fallback_($fallback) {
    @return get-var-fallback_($fallback);
  } @else {
    @return $fallback;
  }
}

@function var_($style) {
  $var: map.get($style, "varname");
  $fallback: map.get($style, "fallback");

  @if is-var-with-fallback_($fallback) {
    @return var(#{$var}, var_($fallback));
  } @else {
    @return var(#{$var}, $fallback);
  }
}

///
/// @param $color Target color in any color format.
/// @return Returns hash in string format that uniquely represents
///     any given color format. Useful for generating unique keyframe names.
/// @example
///   `color-hash(#6200ee)` => "6200ee"
///   `color-hash(rgb(255, 112, 112))` => "ff7070"
///   `color-hash(var(--my-fancy-color))` => "--my-fancy-color"
///
@function color-hash($color) {
  @if is-var-with-fallback_($color) {
    $color: map.get($color, "fallback");
  }

  @if is-css-var_($color) {
    @return get-css-varname_($color);
  }

  @if meta.type-of($color) == "string" {
    @return $color;
  }

  @return string.slice(color.ie-hex-str($color), 2); // Index starts at 1
}

///
/// @return Returns true if given color is set to CSS variable.
/// @access Private
///
@function is-css-var_($color) {
  @return str_slice(meta.inspect($color), 1, 4) == "var(";
}

///
/// @return Returns CSS variable name from color value in CSS variable format.
///     Returns original color value if not in CSS variable format.
/// @example
///   mdc-theme-get-css-varname_(var(--my-fancy-color, #4CAF50)) => --my-fancy-color
///   mdc-theme-get-css-varname_(var(--my-fancy-color)) => --my-fancy-color
/// @access Private
///
@function get-css-varname_($color) {
  @if not is-css-var_($color) {
    @return $color;
  }

  $color: meta.inspect($color);

  $var-start-index: string.index($color, "--");
  $color: str_slice($color, $var-start-index);
  $var-end-index: string.index($color, ",") or string.index($color, ")");
  $color: str_slice($color, 0, $var-end-index - 1);

  @return $color;
}