refactor: address code review feedback

- Remove unused @formatjs/intl-localematcher dependency
- Extract SUPPORTED_LANGUAGES constant to reduce type assertion duplication
- Use Object.fromEntries for more concise header conversion
- Improve code readability and efficiency

Co-authored-by: huangyiirene <7665279+huangyiirene@users.noreply.github.com>

Author: Copilot

apps/docs/middleware.ts

@@ -4,6 +4,11 @@ import { i18n } from '@/lib/i18n';
 
 const LOCALE_COOKIE = 'FD_LOCALE';
 
+/**
+ * Helper to check if a language is supported
+ */
+const SUPPORTED_LANGUAGES = i18n.languages as readonly string[];
+
 /**
  * Language code mapping
  * Maps browser language codes to our supported language codes
@@ -39,16 +44,12 @@ function normalizeLanguage(lang: string): string {
 function getPreferredLanguage(request: NextRequest): string {
   // Check cookie first
   const cookieLocale = request.cookies.get(LOCALE_COOKIE)?.value;
-  if (cookieLocale && (i18n.languages as readonly string[]).includes(cookieLocale)) {
+  if (cookieLocale && SUPPORTED_LANGUAGES.includes(cookieLocale)) {
     return cookieLocale;
   }
 
   // Then check Accept-Language header
-  const negotiatorHeaders: Record<string, string> = {};
-  request.headers.forEach((value, key) => {
-    negotiatorHeaders[key] = value;
-  });
-
+  const negotiatorHeaders = Object.fromEntries(request.headers.entries());
   const negotiator = new Negotiator({ headers: negotiatorHeaders });
   const browserLanguages = negotiator.languages();
 
@@ -57,7 +58,7 @@ function getPreferredLanguage(request: NextRequest): string {
 
   // Find the first match
   for (const lang of normalizedLanguages) {
-    if ((i18n.languages as readonly string[]).includes(lang)) {
+    if (SUPPORTED_LANGUAGES.includes(lang)) {
       return lang;
     }
   }

apps/docs/package.json

@@ -21,7 +21,6 @@
     "server-only": "^0.0.1"
   },
   "devDependencies": {
-    "@formatjs/intl-localematcher": "^0.8.0",
     "@tailwindcss/postcss": "^4.1.18",
     "@tailwindcss/typography": "^0.5.19",
     "@types/negotiator": "^0.6.4",