feat: implement browser language detection and auto-redirect for homepage

apps/docs/middleware.ts

@@ -1,15 +1,135 @@
-import { createI18nMiddleware } from 'fumadocs-core/i18n/middleware';
+import { NextRequest, NextResponse } from 'next/server';
+import Negotiator from 'negotiator';
 import { i18n } from '@/lib/i18n';
 
+const LOCALE_COOKIE = 'FD_LOCALE';
+
+/**
+ * Supported languages extracted from i18n configuration
+ */
+const SUPPORTED_LANGUAGES = i18n.languages as readonly string[];
+
+/**
+ * Set locale cookie with consistent options
+ */
+function setLocaleCookie(response: NextResponse, locale: string): void {
+ response.cookies.set(LOCALE_COOKIE, locale, {
+ sameSite: 'lax',
+ path: '/',
+ });
+}
+
+/**
+ * Language code mapping
+ * Maps browser language codes to our supported language codes
+ */
+const LANGUAGE_MAPPING: Record<string, string> = {
+ 'zh': 'cn', // Chinese -> cn
+ 'zh-CN': 'cn', // Chinese (China) -> cn
+ 'zh-TW': 'cn', // Chinese (Taiwan) -> cn
+ 'zh-HK': 'cn', // Chinese (Hong Kong) -> cn
+};
+
+/**
+ * Normalize language code to match our supported languages
+ */
+function normalizeLanguage(lang: string): string {
+ // Check direct mapping first
+ if (LANGUAGE_MAPPING[lang]) {
+ return LANGUAGE_MAPPING[lang];
+ }
+
+ // Check if the base language (without region) is mapped
+ const baseLang = lang.split('-')[0];
+ if (LANGUAGE_MAPPING[baseLang]) {
+ return LANGUAGE_MAPPING[baseLang];
+ }
+
+ return lang;
+}
+
+/**
+ * Get the preferred language from the request
+ */
+function getPreferredLanguage(request: NextRequest): string {
+ // Check cookie first
+ const cookieLocale = request.cookies.get(LOCALE_COOKIE)?.value;
+ if (cookieLocale && SUPPORTED_LANGUAGES.includes(cookieLocale)) {
+ return cookieLocale;
+ }
+
+ // Then check Accept-Language header
+ const negotiatorHeaders = Object.fromEntries(request.headers.entries());
+ const negotiator = new Negotiator({ headers: negotiatorHeaders });
+ const browserLanguages = negotiator.languages();
+
+ // Normalize browser languages to match our supported languages
+ const normalizedLanguages = browserLanguages.map(normalizeLanguage);
+
+ // Find the first match
+ for (const lang of normalizedLanguages) {
+ if (SUPPORTED_LANGUAGES.includes(lang)) {
+ return lang;
+ }
+ }
+
+ return i18n.defaultLanguage;
+}
+
 /**
  * Middleware for automatic language detection and redirection
  * 
  * This middleware:
  * - Detects the user's preferred language from browser settings or cookies
  * - Redirects users to the appropriate localized version
+ * - For default language (en): keeps URL as "/" (with internal rewrite)
+ * - For other languages (cn): redirects to "/cn/"
  * - Stores language preference as a cookie
  */
-export default createI18nMiddleware(i18n);
+export default function middleware(request: NextRequest) {
+ const { pathname } = request.nextUrl;
+
+ // Check if the pathname already has a locale
+ const pathnameHasLocale = i18n.languages.some(
+ (locale) => pathname.startsWith(`/${locale}/`) || pathname === `/${locale}`
+ );
+
+ if (pathnameHasLocale) {
+ // Extract the locale from the pathname
+ const locale = pathname.split('/')[1];
+
+ // If it's the default locale and hideLocale is 'default-locale', redirect to remove locale prefix
+ if (locale === i18n.defaultLanguage && i18n.hideLocale === 'default-locale') {
+ const url = new URL(request.url);
+ // Remove locale prefix more precisely to avoid issues with partial matches
+ url.pathname = pathname.replace(new RegExp(`^/${i18n.defaultLanguage}(/|$)`), '$1') || '/';
+ const response = NextResponse.redirect(url);
+ setLocaleCookie(response, locale);
+ return response;
+ }
+
+ return NextResponse.next();
+ }
+
+ // Pathname doesn't have a locale, determine preferred language
+ const preferredLanguage = getPreferredLanguage(request);
+
+ // If preferred language is the default, rewrite internally (keep URL clean)
+ if (preferredLanguage === i18n.defaultLanguage && i18n.hideLocale === 'default-locale') {
+ const url = new URL(request.url);
+ // Handle root path specially to avoid double slashes
+ url.pathname = pathname === '/' ? `/${i18n.defaultLanguage}` : `/${i18n.defaultLanguage}${pathname}`;
+ return NextResponse.rewrite(url);
+ }
+
+ // For non-default languages, redirect to the localized path
+ const url = new URL(request.url);
+ // Handle root path specially to avoid double slashes
+ url.pathname = pathname === '/' ? `/${preferredLanguage}` : `/${preferredLanguage}${pathname}`;
+ const response = NextResponse.redirect(url);
+ setLocaleCookie(response, preferredLanguage);
+ return response;
+}
 
 export const config = {
  // Match all routes except:

apps/docs/package.json

@@ -23,10 +23,12 @@
  "devDependencies": {
  "@tailwindcss/postcss": "^4.1.18",
  "@tailwindcss/typography": "^0.5.19",
+ "@types/negotiator": "^0.6.4",
  "@types/node": "^20.10.0",
  "@types/react": "^19.2.8",
  "@types/react-dom": "^19.2.3",
  "autoprefixer": "^10.4.23",
+ "negotiator": "^1.0.0",
  "postcss": "^8.5.6",
  "tailwindcss": "^4.0.0",
  "typescript": "^5.3.0",