fix(i18n): default interface language to english

src/lib/__tests__/init-translations.test.ts

@@ -1,4 +1,5 @@
 import { beforeEach, describe, expect, it, vi } from 'vitest';
+import { DEFAULT_INTERFACE_LANGUAGE, INTERFACE_LANGUAGE_STORAGE_KEY } from '../constants';
 
 const testState = vi.hoisted(() => {
   const i18next = {
@@ -47,10 +48,15 @@ describe('init-translations', () => {
     expect(testState.i18next.use).toHaveBeenNthCalledWith(3, testState.reactPlugin);
     expect(testState.i18next.init).toHaveBeenCalledWith(
       expect.objectContaining({
-        fallbackLng: 'en',
+        fallbackLng: DEFAULT_INTERFACE_LANGUAGE,
         ns: ['default'],
         defaultNS: 'default',
         backend: { loadPath: './translations/{{lng}}/{{ns}}.json' },
+        detection: {
+          order: ['localStorage'],
+          caches: ['localStorage'],
+          lookupLocalStorage: INTERFACE_LANGUAGE_STORAGE_KEY,
+        },
       }),
     );
     expect(testState.i18next.init.mock.calls[0]?.[0]?.supportedLngs).toContain('en');

src/lib/constants.ts

@@ -6,3 +6,47 @@ export const BOARD_REPLIES_PREVIEW_VISIBLE_COUNT = 5;
 
 /** Number of replies fetched for preview mode on board/listing views. */
 export const BOARD_REPLIES_PREVIEW_FETCH_SIZE = 25;
+
+/** 5chan ships in English by default; users must opt into other languages manually. */
+export const DEFAULT_INTERFACE_LANGUAGE = 'en';
+
+/** Persist only deliberate in-app language selections, never OS/browser auto-detection. */
+export const INTERFACE_LANGUAGE_STORAGE_KEY = '5chan-interface-language';
+
+export const SUPPORTED_INTERFACE_LANGUAGES = [
+  'ar',
+  'bn',
+  'cs',
+  'da',
+  'de',
+  'el',
+  'en',
+  'es',
+  'fa',
+  'fi',
+  'fil',
+  'fr',
+  'he',
+  'hi',
+  'hu',
+  'id',
+  'it',
+  'ja',
+  'ko',
+  'mr',
+  'nl',
+  'no',
+  'pl',
+  'pt',
+  'ro',
+  'ru',
+  'sq',
+  'sv',
+  'te',
+  'th',
+  'tr',
+  'uk',
+  'ur',
+  'vi',
+  'zh',
+] as const;

src/lib/init-translations.ts

@@ -2,6 +2,7 @@ import i18next from 'i18next';
 import HttpBackend from 'i18next-http-backend';
 import LanguageDetector from 'i18next-browser-languagedetector';
 import { initReactI18next } from 'react-i18next';
+import { DEFAULT_INTERFACE_LANGUAGE, INTERFACE_LANGUAGE_STORAGE_KEY, SUPPORTED_INTERFACE_LANGUAGES } from './constants';
 
 const loadPath = `./translations/{{lng}}/{{ns}}.json`;
 
@@ -10,44 +11,13 @@ i18next
   .use(LanguageDetector)
   .use(initReactI18next)
   .init({
-    fallbackLng: 'en',
-    supportedLngs: [
-      'ar',
-      'bn',
-      'cs',
-      'da',
-      'de',
-      'el',
-      'en',
-      'es',
-      'fa',
-      'fi',
-      'fil',
-      'fr',
-      'he',
-      'hi',
-      'hu',
-      'id',
-      'it',
-      'ja',
-      'ko',
-      'mr',
-      'nl',
-      'no',
-      'pl',
-      'pt',
-      'ro',
-      'ru',
-      'sq',
-      'sv',
-      'te',
-      'th',
-      'tr',
-      'uk',
-      'ur',
-      'vi',
-      'zh',
-    ],
+    fallbackLng: DEFAULT_INTERFACE_LANGUAGE,
+    supportedLngs: [...SUPPORTED_INTERFACE_LANGUAGES],
+    detection: {
+      order: ['localStorage'],
+      caches: ['localStorage'],
+      lookupLocalStorage: INTERFACE_LANGUAGE_STORAGE_KEY,
+    },
 
     ns: ['default'],
     defaultNS: 'default',