@use '../m2/palette';
@use '../m2/theming';
@use '../m2/typography';
@use 'sass:color';
@use 'sass:math';
@use 'sass:meta';

$_placeholder-color-palette: theming.define-palette(palette.$red-palette);

// Indicates whether we're building internally. Used for backwards compatibility.
$private-is-internal-build: false;

// Placeholder color config that can be passed to token getter functions when generating token
// slots.
$placeholder-color-config: (
  primary: $_placeholder-color-palette,
  accent: $_placeholder-color-palette,
  warn: $_placeholder-color-palette,
  is-dark: false,
  foreground: palette.$light-theme-foreground-palette,
  background: palette.$light-theme-background-palette,
);

$_placeholder-typography-level-config: typography.typography-config-level-from-mdc(body1);

// Placeholder typography config that can be passed to token getter functions when generating token
// slots.
$placeholder-typography-config: (
  font-family: 'Roboto, sans-serif',
  headline-1: $_placeholder-typography-level-config,
  headline-2: $_placeholder-typography-level-config,
  headline-3: $_placeholder-typography-level-config,
  headline-4: $_placeholder-typography-level-config,
  headline-5: $_placeholder-typography-level-config,
  headline-6: $_placeholder-typography-level-config,
  subtitle-1: $_placeholder-typography-level-config,
  subtitle-2: $_placeholder-typography-level-config,
  body-1: $_placeholder-typography-level-config,
  body-2: $_placeholder-typography-level-config,
  caption: $_placeholder-typography-level-config,
  button: $_placeholder-typography-level-config,
  overline: $_placeholder-typography-level-config,
  subheading-1: $_placeholder-typography-level-config,
  title: $_placeholder-typography-level-config,
);

// Placeholder density config that can be passed to token getter functions when generating token
// slots.
$placeholder-density-config: 0;

/// Inherited function from MDC that computes which contrast tone to use on top of a color.
/// This is used only in a narrow set of use cases when generating M2 button tokens to maintain
/// backwards compatibility.
/// @param {Color} $value Color for which we're calculating the contrast tone.
/// @param {Boolean} $is-dark Whether the current theme is dark.
/// @return {Map} Either `dark` or `light`.
@function contrast-tone($value, $is-dark) {
  @if ($value == 'dark') {
    @return 'light';
  }

  @if ($value == 'light') {
    @return 'dark';
  }

  // Fallback if the app is using a non-color palette (e.g. CSS variable based).
  @if (meta.type-of($value) != 'color') {
    @return if($is-dark, 'light', 'dark');
  }

  $minimum-contrast: 3.1;
  $light-contrast: _contrast($value, #fff);
  $dark-contrast: _contrast($value, rgba(0, 0, 0, 0.87));

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

  @return 'light';
}

@function _linear-channel-value($channel-value) {
  $normalized-channel-value: math.div($channel-value, 255);

  @if ($normalized-channel-value < 0.03928) {
    @return math.div($normalized-channel-value, 12.92);
  }

  @return math.pow(math.div($normalized-channel-value + 0.055, 1.055), 2.4);
}

// Calculate the luminance for a color.
// See https://www.w3.org/TR/WCAG20-TECHS/G17.html#G17-tests
@function _luminance($color) {
  $red: _linear-channel-value(color.red($color));
  $green: _linear-channel-value(color.green($color));
  $blue: _linear-channel-value(color.blue($color));

  @return 0.2126 * $red + 0.7152 * $green + 0.0722 * $blue;
}

// Calculate the contrast ratio between two colors.
// See https://www.w3.org/TR/WCAG20-TECHS/G17.html#G17-tests
@function _contrast($back, $front) {
  $back-lum: _luminance($back) + 0.05;
  $fore-lum: _luminance($front) + 0.05;

  @return math.div(math.max($back-lum, $fore-lum), math.min($back-lum, $fore-lum));
}