feat(styles): add palettes (#3850)

To ease the review, the changes are grouped into 3 commits: 

- feat(styles): add palette styles
- feat(docs): add palette stories
- chore: add palette tests

.changeset/weak-jars-rhyme.md

@@ -0,0 +1,6 @@
+---
+'@swisspost/design-system-documentation': minor
+'@swisspost/design-system-styles': minor
+---
+
+Added color palettes to easily apply colors to a page section using predefined color sets.

packages/documentation/cypress/e2e/components/palette.cy.ts

@@ -0,0 +1,13 @@
+describe('Palette', () => {
+  describe('Accessibility', () => {
+    beforeEach(() => {
+      cy.visit('/iframe.html?id=snapshots--palette');
+      cy.get('.palette-default', { timeout: 30000 }).should('be.visible');
+      cy.injectAxe();
+    });
+
+    it('Has no detectable a11y violations on load for all variants', () => {
+      cy.checkA11y('#root-inner');
+    });
+  });
+});

packages/documentation/cypress/snapshots/components/palette.snapshot.ts

@@ -0,0 +1,7 @@
+describe('Palette', () => {
+  it('default', () => {
+    cy.visit('/iframe.html?id=snapshots--palette');
+    cy.get('.palette-default', { timeout: 30000 }).should('be.visible');
+    cy.percySnapshot('Palettes', { widths: [1440] });
+  });
+});

packages/documentation/src/stories/foundation/palette/palette.docs.mdx

@@ -0,0 +1,27 @@
+import { Canvas, Controls, Meta } from '@storybook/blocks';
+import * as paletteStories from './palette.stories';
+
+<Meta of={paletteStories} />
+
+<div className="docs-title">
+  # Palettes
+</div>
+
+<div className="lead">
+  Easily apply colors to a section of your page using predefined color sets.
+</div>
+
+There are four different palettes:
+- **Default** - The standard palette used when no other palette is specified.
+- **Alternate** - Used to differentiate alternating sections from the body, without strong emphasis or highlighting.
+- **Accent** - A complementary color used for highlights and emphasis.
+- **Brand** - The primary color for the brand.
+
+Palettes may also include a specific text color that is different from the body color.
+You can apply this text color to any element by using the `.palette-text` class.
+
+<Canvas sourceState="shown" of={paletteStories.Default} />
+
+<div className="hide-col-default">
+  <Controls of={paletteStories.Default} />
+</div>

packages/documentation/src/stories/foundation/palette/palette.snapshot.stories.ts

@@ -0,0 +1,35 @@
+import type { StoryObj } from '@storybook/web-components';
+import { html } from 'lit';
+import meta from './palette.stories';
+
+const { id, ...metaWithoutId } = meta;
+
+export default {
+  ...metaWithoutId,
+  title: 'Snapshots',
+};
+
+type Story = StoryObj;
+
+export const Palette: Story = {
+  render: () => {
+    return html`${['light', 'dark'].map(
+      mainScheme => html`
+        <div class="palette-default p-24 d-flex flex-column gap-48" data-color-scheme=${mainScheme}>
+          ${['', 'light', 'dark'].map(
+            paletteScheme => html`
+              <div>
+                <p class="px-24">Palette scheme: ${paletteScheme || 'none'}</p>
+                <div class="d-flex">
+                  ${meta.argTypes.palette.options.map(palette =>
+                    meta.render({ palette, colorScheme: paletteScheme }),
+                  )}
+                </div>
+              </div>
+            `,
+          )}
+        </div>
+      `,
+    )}`;
+  },
+};

packages/documentation/src/stories/foundation/palette/palette.stories.ts

@@ -0,0 +1,58 @@
+import { Args, Meta, StoryObj } from '@storybook/web-components';
+import { html, nothing } from 'lit';
+
+const meta: Meta = {
+  id: '43481535-5b39-40b5-a273-478b07dc3b31',
+  title: 'Foundations/Palettes',
+  tags: ['package:HTML'],
+  render: renderPalette,
+  parameters: {
+    palettes: [],
+    design: {
+      type: 'figma',
+      url: 'https://www.figma.com/file/xZ0IW0MJO0vnFicmrHiKaY/Components-Post?type=design&node-id=18172-73431&mode=design&t=3lniLiZhl7q9Gqgn-4',
+    },
+  },
+  args: {
+    palette: 'default',
+  },
+  argTypes: {
+    palette: {
+      name: 'Palette',
+      description: 'The set of colors used for a section of the page.',
+      control: {
+        type: 'radio',
+        labels: {
+          default: 'Default',
+          alternate: 'Alternate',
+          brand: 'Brand',
+          accent: 'Accent',
+        },
+      },
+      options: ['default', 'alternate', 'accent', 'brand'],
+      table: {
+        category: 'General',
+      },
+    },
+  },
+};
+
+export default meta;
+
+// RENDERER
+function renderPalette(args: Args) {
+  return html`
+    <div class="palette-${args.palette} p-24" data-color-scheme=${args.colorScheme ?? nothing}>
+      <h2 class="palette-text">
+        I use a specific color from the palette (it might be the same as the body color).
+      </h2>
+      <p>I use the main body color.</p>
+      <button class="btn btn-primary">Primary button</button>
+    </div>
+  `;
+}
+
+// STORIES
+type Story = StoryObj;
+
+export const Default: Story = {};

packages/styles/gulpfile.js

@@ -27,7 +27,7 @@ gulp.task('copy', () => {
  * See https://github.com/pnpm/pnpm/issues/8338 for more information and reproduction
  */
 gulp.task('temporarily-copy-token-files', () => {
-  return gulp.src(['../tokens/dist/*.scss']).pipe(gulp.dest('./src/tokens/temp'));
+  return gulp.src(['../tokens/dist/**/*.scss']).pipe(gulp.dest('./src/tokens/temp'));
 });
 
 /**

packages/styles/src/cargo-external.scss

@@ -2,6 +2,7 @@
 @use './tokens/device';
 @use './tokens/external';
 @use './tokens/cargo-theme';
+@use './palettes/cargo-palettes';
 @use './utilities';
 @use './elements';
 @use './components';

packages/styles/src/cargo-internal.scss

@@ -2,6 +2,7 @@
 @use './tokens/device';
 @use './tokens/internal';
 @use './tokens/cargo-theme';
+@use './palettes/cargo-palettes';
 @use './utilities';
 @use './elements';
 @use './components';

packages/styles/src/palettes/_mixins.scss

@@ -0,0 +1,74 @@
+@use 'sass:map';
+@use 'sass:meta';
+
+@use '../functions/tokens';
+@use '../placeholders/schemes';
+@use '../tokens/elements';
+@use '../tokens/palettes';
+
+@use './variables' as *;
+
+@forward './utilities';
+
+@mixin palettes($theme) {
+  body {
+    background-color: var(--post-current-palette-bg) !important;
+
+    &:not([data-color-scheme='dark']) {
+      @include palette-tokens($default-palette, $theme, 'light');
+    }
+
+    &[data-color-scheme='dark'] {
+      @include palette-tokens($default-palette, $theme, 'dark');
+    }
+  }
+
+  @each $palette in $palettes {
+    .palette-#{$palette} {
+      // Redefining the body color is necessary to ensure that the new color scheme is applied correctly.
+      // Known limitation: body color may be incorrect with nested parent with different `data-color-scheme` values.
+      color: tokens.get('body-color', elements.$post-body);
+      background-color: var(--post-current-palette-bg) !important;
+
+      // Light scheme explicitly set on the palette:
+      &[data-color-scheme='light'],
+
+      // No scheme explicitly set on the palette, but parent has a light scheme:
+      &:where([data-color-scheme='light'] :not([data-color-scheme='dark'])),
+
+      // No scheme explicitly set on the palette, and no scheme on the parent either:
+      &:not([data-color-scheme='dark']):not([data-color-scheme='dark'] *) {
+        @include palette-tokens($palette, $theme, 'light', $override-scheme: true);
+      }
+
+      // Dark scheme explicitly set on the palette:
+      &[data-color-scheme='dark'],
+
+      // No scheme explicitly set on the palette, but parent has a dark scheme:
+      &:where([data-color-scheme='dark'] :not([data-color-scheme='dark'])) {
+        @include palette-tokens($palette, $theme, 'dark', $override-scheme: true);
+      }
+    }
+  }
+}
+
+@mixin palette-tokens($name, $theme, $scheme, $override-scheme: false) {
+  $palette: map.get(meta.module-variables(palettes), '#{$theme}-#{$scheme}');
+
+  @if (not $palette) {
+    @error 'Palette #{$theme}-#{$scheme} not found.';
+  }
+
+  --post-current-palette-fg: #{tokens.get('palettes-color-#{$name}-fg', $palette)};
+  --post-current-palette-bg: #{tokens.get('palettes-color-#{$name}-bg', $palette)};
+
+  @if ($override-scheme == true) {
+    $bg-scheme: tokens.get('palettes-color-#{$name}-bg-scheme', $palette);
+
+    @if ($bg-scheme == 'light') {
+      @extend %color-scheme-light;
+    } @else {
+      @extend %color-scheme-dark;
+    }
+  }
+}

packages/styles/src/palettes/_utilities.scss

@@ -0,0 +1,3 @@
+.palette-text {
+  color: var(--post-current-palette-fg);
+}

packages/styles/src/palettes/_variables.scss

@@ -0,0 +1,2 @@
+$default-palette: 'default';
+$palettes: $default-palette, 'alternate', 'brand', 'accent';

packages/styles/src/palettes/cargo-palettes.scss

@@ -0,0 +1,3 @@
+@use 'mixins' as *;
+
+@include palettes('cargo');

packages/styles/src/palettes/post-palettes.scss

@@ -0,0 +1,3 @@
+@use 'mixins' as *;
+
+@include palettes('post');

packages/styles/src/post-external.scss

@@ -2,6 +2,7 @@
 @use './tokens/device';
 @use './tokens/external';
 @use './tokens/post-theme';
+@use './palettes/post-palettes';
 @use './utilities';
 @use './elements';
 @use './components';

packages/styles/src/post-internal.scss

@@ -2,6 +2,7 @@
 @use './tokens/device';
 @use './tokens/internal';
 @use './tokens/post-theme';
+@use './palettes/post-palettes';
 @use './utilities';
 @use './elements';
 @use './components';

packages/styles/src/tokens/_palettes.scss

@@ -0,0 +1,9 @@
+@use './temp/palettes/post-light' as post-light;
+@use './temp/palettes/post-dark' as post-dark;
+@use './temp/palettes/cargo-light' as cargo-light;
+@use './temp/palettes/cargo-dark' as cargo-dark;
+
+$post-light: post-light.$post-palettes;
+$post-dark: post-dark.$post-palettes;
+$cargo-light: cargo-light.$post-palettes;
+$cargo-dark: cargo-dark.$post-palettes;

packages/styles/tests/palettes/cargo-palettes.test.scss

@@ -0,0 +1,10 @@
+@use 'src/palettes/cargo-palettes';
+
+/* stylelint-disable scss/at-extend-no-missing-placeholder */
+.palettes {
+  @extend .palette-text;
+  @extend .palette-default;
+  @extend .palette-alternate;
+  @extend .palette-brand;
+  @extend .palette-accent;
+}

packages/styles/tests/palettes/post-palettes.test.scss

@@ -0,0 +1,10 @@
+@use 'src/palettes/post-palettes';
+
+/* stylelint-disable scss/at-extend-no-missing-placeholder */
+.palettes {
+  @extend .palette-text;
+  @extend .palette-default;
+  @extend .palette-alternate;
+  @extend .palette-brand;
+  @extend .palette-accent;
+}