Add system theme preference to the storefront.

Default to system when no theme cookie is set so pages follow OS appearance, and expose Light, Dark, and System in the theme switcher.

backend/src/consts/storefrontThemePreferences.ts

@@ -0,0 +1 @@
+export const STOREFRONT_THEME_PREFERENCES = ['light', 'dark', 'system'] as const;

backend/src/modules/storefrontCore/dto/SetThemePreferenceDto.ts

@@ -1,8 +1,9 @@
 import { IsIn, IsNotEmpty } from 'class-validator';
+import { STOREFRONT_THEME_PREFERENCES } from '../../../consts/storefrontThemePreferences';
 import type { StorefrontThemePreference } from '../types/StorefrontThemePreference';
 
 export class SetThemePreferenceDto {
     @IsNotEmpty()
-    @IsIn(['light', 'dark'])
+    @IsIn(STOREFRONT_THEME_PREFERENCES)
     theme: StorefrontThemePreference;
 }

backend/src/modules/storefrontCore/services/StorefrontShopViewService.spec.ts

@@ -8,39 +8,21 @@ import { StorefrontFeedbackCookieService } from './StorefrontFeedbackCookieServi
 import { StorefrontOrderAuthCookieService } from './StorefrontOrderAuthCookieService';
 import { StorefrontThemeCookieService } from './StorefrontThemeCookieService';
 import type { StorefrontPageMetaInput } from '../types/StorefrontPageMetaInput';
+import type { StorefrontShopViewServiceOverrides } from '../types/StorefrontShopViewServiceTestTypes';
 import { PaymentMethod } from '../../payment/types/PaymentMethod';
 
 describe('StorefrontShopViewService', () => {
-    type ServiceOverrides = {
-        cart?: { variantId: string; qty: number }[];
-        feedback?: { type: 'success'; text: string };
-        authorizedOrderIds?: string[];
-        theme?: 'light' | 'dark';
-        branding?: {
-            logoUrl: string | null;
-            faviconUrl: string | null;
-            simplexLink: string | null;
-            shippingNote: string | null;
-        };
-        shopSettings?: { shopName: string; shopFiatCurrency: string; enabledPaymentMethods?: PaymentMethod[] };
-        fiatPerXmr?: number;
-        fiatPerBtc?: number | null;
-        req?: Partial<Pick<Request, 'protocol' | 'path' | 'originalUrl'>> & {
-            host?: string;
-        };
-    };
-
     const defaultPage: StorefrontPageMetaInput = {
         title: 'Cart',
         metaDescription: 'Review your cart.'
     };
 
-    const createService = (overrides: ServiceOverrides = {}) => {
+    const createService = (overrides: StorefrontShopViewServiceOverrides = {}) => {
         const {
             cart = [],
             feedback,
             authorizedOrderIds = [],
-            theme,
+            theme = 'system',
             branding = {
                 logoUrl: null,
                 faviconUrl: null,
@@ -117,6 +99,7 @@ describe('StorefrontShopViewService', () => {
             ogImageUrl: null,
             productJsonLd: null
         });
+        expect(locals.themePreference).toBe('system');
     });
 
     it('exposes shop settings, cart qty, feedback, branding, theme, and request context', async () => {

backend/src/modules/storefrontCore/services/StorefrontThemeCookieService.spec.ts

@@ -14,10 +14,16 @@ describe('StorefrontThemeCookieService', () => {
         service = new StorefrontThemeCookieService(signedCookies as unknown as StorefrontSignedCookieService);
     });
 
-    it('returns undefined for invalid theme values', () => {
-        signedCookies.getSignedCookie.mockReturnValue({ theme: 'system' });
+    it('returns system when no cookie is set', () => {
+        signedCookies.getSignedCookie.mockReturnValue(undefined);
 
-        expect(service.getTheme({} as never, {} as never)).toBeUndefined();
+        expect(service.getTheme({} as never, {} as never)).toBe('system');
+    });
+
+    it('returns system for invalid theme values', () => {
+        signedCookies.getSignedCookie.mockReturnValue({ theme: 'sepia' });
+
+        expect(service.getTheme({} as never, {} as never)).toBe('system');
     });
 
     it('returns a supported theme preference', () => {
@@ -25,4 +31,10 @@ describe('StorefrontThemeCookieService', () => {
 
         expect(service.getTheme({} as never, {} as never)).toBe('dark');
     });
+
+    it('returns system when stored in the cookie', () => {
+        signedCookies.getSignedCookie.mockReturnValue({ theme: 'system' });
+
+        expect(service.getTheme({} as never, {} as never)).toBe('system');
+    });
 });

backend/src/modules/storefrontCore/services/StorefrontThemeCookieService.ts

@@ -1,5 +1,6 @@
 import { Injectable } from '@nestjs/common';
 import type { Request, Response } from 'express';
+import { STOREFRONT_THEME_PREFERENCES } from '../../../consts/storefrontThemePreferences';
 import type { StorefrontThemePreference } from '../types/StorefrontThemePreference';
 import { StorefrontSignedCookieService } from './StorefrontSignedCookieService';
 
@@ -7,15 +8,15 @@ import { StorefrontSignedCookieService } from './StorefrontSignedCookieService';
 export class StorefrontThemeCookieService {
     constructor(private readonly signedCookies: StorefrontSignedCookieService) {}
 
-    getTheme(req: Request, res: Response): StorefrontThemePreference | undefined {
-        const payload = this.signedCookies.getSignedCookie<{ theme: string }>(req, res, 'theme');
+    getTheme(req: Request, res: Response): StorefrontThemePreference {
+        const payload = this.signedCookies.getSignedCookie<{ theme: StorefrontThemePreference }>(req, res, 'theme');
         const theme = payload?.theme;
 
-        if (theme === 'light' || theme === 'dark') {
+        if (theme && STOREFRONT_THEME_PREFERENCES.includes(theme)) {
             return theme;
         }
 
-        return undefined;
+        return 'system';
     }
 
     setTheme(req: Request, res: Response, theme: StorefrontThemePreference): void {

backend/src/modules/storefrontCore/types/ShopRenderLocals.ts

@@ -19,6 +19,6 @@ export type ShopRenderLocals = {
     faviconUrl: string | null;
     simplexLink: string | null;
     shippingNote: string | null;
-    themePreference: StorefrontThemePreference | undefined;
+    themePreference: StorefrontThemePreference;
     pageMeta: StorefrontPageMeta;
 };

backend/src/modules/storefrontCore/types/StorefrontShopViewServiceTestTypes.ts

@@ -0,0 +1,22 @@
+import type { Request } from 'express';
+import type { PaymentMethod } from '../../payment/types/PaymentMethod';
+import type { StorefrontThemePreference } from './StorefrontThemePreference';
+
+export type StorefrontShopViewServiceOverrides = {
+    cart?: { variantId: string; qty: number }[];
+    feedback?: { type: 'success'; text: string };
+    authorizedOrderIds?: string[];
+    theme?: StorefrontThemePreference;
+    branding?: {
+        logoUrl: string | null;
+        faviconUrl: string | null;
+        simplexLink: string | null;
+        shippingNote: string | null;
+    };
+    shopSettings?: { shopName: string; shopFiatCurrency: string; enabledPaymentMethods?: PaymentMethod[] };
+    fiatPerXmr?: number;
+    fiatPerBtc?: number | null;
+    req?: Partial<Pick<Request, 'protocol' | 'path' | 'originalUrl'>> & {
+        host?: string;
+    };
+};

backend/src/modules/storefrontCore/types/StorefrontThemePreference.ts

@@ -1 +1,3 @@
-export type StorefrontThemePreference = 'light' | 'dark';
+import { STOREFRONT_THEME_PREFERENCES } from '../../../consts/storefrontThemePreferences';
+
+export type StorefrontThemePreference = (typeof STOREFRONT_THEME_PREFERENCES)[number];

backend/src/modules/storefrontCore/utils/registerStorefrontPartials.ts

@@ -29,6 +29,7 @@ const STOREFRONT_PARTIALS = [
     { name: 'shop-footer', file: 'shop-footer.hbs' },
     { name: 'storefront-image', file: 'storefront-image.hbs' },
     { name: 'theme-switcher', file: 'theme-switcher.hbs' },
+    { name: 'html-theme-attributes', file: 'html-theme-attributes.hbs' },
     { name: 'page-back-link', file: 'page-back-link.hbs' },
     { name: 'product-card', file: 'product-card.hbs' },
     { name: 'order-data-retention-notice', file: 'order-data-retention-notice.hbs' },

backend/src/modules/storefrontCore/views/layouts/shop-minimal.hbs

@@ -1,8 +1,7 @@
 <!DOCTYPE html>
 <html
     lang='en'
-    {{#ifeq themePreference 'light'}}data-theme='light'{{/ifeq}}
-    {{#ifeq themePreference 'dark'}}data-theme='dark'{{/ifeq}}
+    {{> html-theme-attributes}}
 >
     <head>
         {{> shop-head}}

backend/src/modules/storefrontCore/views/layouts/shop.hbs

@@ -1,8 +1,7 @@
 <!DOCTYPE html>
 <html
     lang='en'
-    {{#ifeq themePreference 'light'}}data-theme='light'{{/ifeq}}
-    {{#ifeq themePreference 'dark'}}data-theme='dark'{{/ifeq}}
+    {{> html-theme-attributes}}
 >
     <head>
         {{> shop-head}}

backend/src/modules/storefrontCore/views/partials/html-theme-attributes.hbs

@@ -0,0 +1,2 @@
+{{#ifeq themePreference 'light'}}data-theme='light'{{/ifeq}}
+{{#ifeq themePreference 'dark'}}data-theme='dark'{{/ifeq}}

backend/src/modules/storefrontCore/views/partials/theme-switcher.hbs

@@ -15,5 +15,12 @@
             class='sf-btn sf-btn--sm{{#ifeq themePreference 'dark'}} sf-btn--primary{{/ifeq}}'
             {{#ifeq themePreference 'dark'}}aria-current='true'{{/ifeq}}
         >Dark</button>
+        <button
+            type='submit'
+            name='theme'
+            value='system'
+            class='sf-btn sf-btn--sm{{#ifeq themePreference 'system'}} sf-btn--primary{{/ifeq}}'
+            {{#ifeq themePreference 'system'}}aria-current='true'{{/ifeq}}
+        >System</button>
     </form>
 </div>