_typography.scss

@use 'sass:map';
@use 'typography-utils';
@use '../theming/theming';

/// Defines a typography level from the Material Design spec.
/// @param {String} $font-size The font-size for this level.
/// @param {String | Number} $line-height The line-height for this level.
/// @param {String | Number} $font-weight The font-weight for this level.
/// @param {String} $font-family The font-family for this level.
/// @param {String} $letter-spacing The letter-spacing for this level.
/// @returns {Map} A map representing the definition of this typpographic level.
@function define-typography-level(
  $font-size,
  $line-height: $font-size,
  $font-weight: 400,
  $font-family: null,
  $letter-spacing: normal) {

  @return (
    font-size: $font-size,
    line-height: $line-height,
    font-weight: $font-weight,
    font-family: $font-family,
    letter-spacing: $letter-spacing
  );
}

/// Defines a collection of typography levels to configure typography for an application.
/// Any level not specified defaults to the values defined in the Material Design specification:
/// https://material.io/guidelines/style/typography.html.
///
/// Note that the Material Design specification does not describe explicit letter-spacing values.
/// The values here come from reverse engineering the Material Design examples.
/// @param {String} $font-family Default font-family for levels that don't specify font-family.
/// @param {Map} $display-4 Configuration for the "display-4" typographic level.
/// @param {Map} $display-3 Configuration for the "display-3" typographic level.
/// @param {Map} $display-2 Configuration for the "display-2" typographic level.
/// @param {Map} $display-1 Configuration for the "display-1" typographic level.
/// @param {Map} $headline Configuration for the "headline" typographic level.
/// @param {Map} $title Configuration for the "title" typographic level.
/// @param {Map} $subheading-2 Configuration for the "subheading-2" typographic level.
/// @param {Map} $subheading-1 Configuration for the "subheading-1" typographic level.
/// @param {Map} $body-2 Configuration for the "body-2" typographic level.
/// @param {Map} $body-1 Configuration for the "body-1" typographic level.
/// @param {Map} $caption Configuration for the "caption" typographic level.
/// @param {Map} $button Configuration for the "button" typographic level.
/// @param {Map} $input Configuration for the "input" typographic level.
/// @returns {Map} A typography config for the application.
@function define-typography-config(
  $font-family:   'Roboto, "Helvetica Neue", sans-serif',
  $display-4:     define-typography-level(112px, 112px, 300, $letter-spacing: -0.05em),
  $display-3:     define-typography-level(56px, 56px, 400, $letter-spacing: -0.02em),
  $display-2:     define-typography-level(45px, 48px, 400, $letter-spacing: -0.005em),
  $display-1:     define-typography-level(34px, 40px, 400),
  $headline:      define-typography-level(24px, 32px, 400),
  $title:         define-typography-level(20px, 32px, 500),
  $subheading-2:  define-typography-level(16px, 28px, 400),
  $subheading-1:  define-typography-level(15px, 24px, 400),
  $body-2:        define-typography-level(14px, 24px, 500),
  $body-1:        define-typography-level(14px, 20px, 400),
  $caption:       define-typography-level(12px, 20px, 400),
  $button:        define-typography-level(14px, 14px, 500),
  // Line-height must be unit-less fraction of the font-size.
  $input:         define-typography-level(inherit, 1.125, 400)
) {

  // Declare an initial map with all of the levels.
  $config: (
    display-4:      $display-4,
    display-3:      $display-3,
    display-2:      $display-2,
    display-1:      $display-1,
    headline:       $headline,
    title:          $title,
    subheading-2:   $subheading-2,
    subheading-1:   $subheading-1,
    body-2:         $body-2,
    body-1:         $body-1,
    caption:        $caption,
    button:         $button,
    input:          $input,
  );

  // Loop through the levels and set the `font-family` of the ones that don't have one to the base.
  // Note that Sass can't modify maps in place, which means that we need to merge and re-assign.
  @each $key, $level in $config {
    @if map.get($level, font-family) == null {
      $new-level: map.merge($level, (font-family: $font-family));
      $config: map.merge($config, ($key: $new-level));
    }
  }

  // Add the base font family to the config.
  @return map.merge($config, (font-family: $font-family));
}

// Whether a config is for the Material Design 2018 typography system.
@function private-typography-is-2018-config($config) {
  @return map.get($config, headline-1) != null;
}

// Whether a config is for the Material Design 2014 typography system.
@function private-typography-is-2014-config($config) {
  @return map.get($config, headline) != null;
}

// Given a config for either the 2014 or 2018 Material Design typography system,
// produces a normalized typography config for the 2014 Material Design typography system.
// 2014 - https://material.io/archive/guidelines/style/typography.html#typography-styles
// 2018 - https://material.io/design/typography/the-type-system.html#type-scale
//
// Components using this function should be migrated to normalize to the 2018 style config instead.
// New components should not use this function.
@function private-typography-to-2014-config($config) {
  @if $config == null {
    @return null;
  }
  @if not private-typography-is-2014-config($config) {
    $args: (
        display-4: map.get($config, headline-1),
        display-3: map.get($config, headline-2),
        display-2: map.get($config, headline-3),
        display-1: map.get($config, headline-4),
        headline: map.get($config, headline-5),
        title: map.get($config, headline-6),
        subheading-2: map.get($config, subtitle-1),
        subheading-1: map.get($config, subtitle-2),
        body-2: map.get($config, body-1),
        body-1: map.get($config, body-2),
        button: map.get($config, button),
        caption: map.get($config, caption),
    );
    $non-null-args: ();
    @each $key, $value in $args {
      @if $value != null {
        $non-null-args: map.merge($non-null-args, ($key: $value));
      }
    }
    @return define-typography-config($non-null-args...);
  }
  @return $config;
}

// Given a config for either the 2014 or 2018 Material Design typography system,
// produces a normalized typography config for the 2018 Material Design typography system.
// 2014 - https://material.io/archive/guidelines/style/typography.html#typography-styles
// 2018 - https://material.io/design/typography/the-type-system.html#type-scale
@function private-typography-to-2018-config($config) {
  @if $config == null {
    @return null;
  }
  @if not private-typography-is-2018-config($config) {
    @return (
        headline-1: map.get($config, display-4),
        headline-2: map.get($config, display-3),
        headline-3: map.get($config, display-2),
        headline-4: map.get($config, display-1),
        headline-5: map.get($config, headline),
        headline-6: map.get($config, title),
        subtitle-1: map.get($config, subheading-2),

        // These mappings are odd, but body-2 in the 2014 system actually looks closer to subtitle-2
        // in the 2018 system, and subeading-1 in the 2014 system looks more like body-1 in the 2018
        // system.
        subtitle-2: map.get($config, body-2),
        body-1: map.get($config, subheading-1),

        body-2: map.get($config, body-1),
        button: map.get($config, button),
        caption: map.get($config, caption),
        overline: if(map.get($config, overline), map.get($config, overline),
            define-typography-level(12px, 32px, 500)
        )
    );
  }
  @return $config;
}

// stylelint-disable material/theme-mixin-api

/// Emits baseline typographic styles based on a given config.
/// @param {Map} $config-or-theme A typography config for an entire theme.
/// @param {String} $selector Ancestor selector under which native elements, such as h1, will
///     be styled.
@mixin typography-hierarchy($config-or-theme, $selector: '.mat-typography') {
  $config: private-typography-to-2014-config(theming.get-typography-config($config-or-theme));

  .mat-h1, .mat-headline, #{$selector} h1 {
    @include typography-utils.typography-level($config, headline);
    margin: 0 0 16px;
  }

  .mat-h2, .mat-title, #{$selector} h2 {
    @include typography-utils.typography-level($config, title);
    margin: 0 0 16px;
  }

  .mat-h3, .mat-subheading-2, #{$selector} h3 {
    @include typography-utils.typography-level($config, subheading-2);
    margin: 0 0 16px;
  }

  .mat-h4, .mat-subheading-1, #{$selector} h4 {
    @include typography-utils.typography-level($config, subheading-1);
    margin: 0 0 16px;
  }

  // Note: the spec doesn't have anything that would correspond to h5 and h6, but we add these for
  // consistency. The font sizes come from the Chrome user agent styles which have h5 at 0.83em
  // and h6 at 0.67em.
  .mat-h5, #{$selector} h5 {
    @include typography-utils.font-shorthand(
       // calc is used here to support css variables
      calc(#{typography-utils.font-size($config, body-1)} * 0.83),
      typography-utils.font-weight($config, body-1),
      typography-utils.line-height($config, body-1),
      typography-utils.font-family($config, body-1)
    );

    margin: 0 0 12px;
  }

  .mat-h6, #{$selector} h6 {
    @include typography-utils.font-shorthand(
       // calc is used here to support css variables
      calc(#{typography-utils.font-size($config, body-1)} * 0.67),
      typography-utils.font-weight($config, body-1),
      typography-utils.line-height($config, body-1),
      typography-utils.font-family($config, body-1)
    );

    margin: 0 0 12px;
  }

  .mat-body-strong, .mat-body-2 {
    @include typography-utils.typography-level($config, body-2);
  }

  .mat-body, .mat-body-1, #{$selector} {
    @include typography-utils.typography-level($config, body-1);

    p {
      margin: 0 0 12px;
    }
  }

  .mat-small, .mat-caption {
    @include typography-utils.typography-level($config, caption);
  }

  .mat-display-4, #{$selector} .mat-display-4 {
    @include typography-utils.typography-level($config, display-4);
    margin: 0 0 56px;
  }

  .mat-display-3, #{$selector} .mat-display-3 {
    @include typography-utils.typography-level($config, display-3);
    margin: 0 0 64px;
  }

  .mat-display-2, #{$selector} .mat-display-2 {
    @include typography-utils.typography-level($config, display-2);
    margin: 0 0 64px;
  }

  .mat-display-1, #{$selector} .mat-display-1 {
    @include typography-utils.typography-level($config, display-1);
    margin: 0 0 64px;
  }
}

// stylelint-enable material/theme-mixin-api