From 00ffe80e13868c98809b519e88e7e7aa27e2fe69 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Fri, 16 Jan 2026 10:04:13 +0000
Subject: [PATCH 1/3] Initial plan


From 77697eb7cd87ddc07dfe1c3aa38b9e4bd101db4c Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Fri, 16 Jan 2026 10:11:06 +0000
Subject: [PATCH 2/3] Implement automatic language detection and redirection

Co-authored-by: huangyiirene <7665279+huangyiirene@users.noreply.github.com>
---
 app/page.tsx | 45 +++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 43 insertions(+), 2 deletions(-)

diff --git a/app/page.tsx b/app/page.tsx
index 839988d..903f940 100644
--- a/app/page.tsx
+++ b/app/page.tsx
@@ -1,5 +1,46 @@
 import { redirect } from 'next/navigation';
+import { headers } from 'next/headers';
+import { i18n } from '@/lib/i18n';
 
-export default function HomePage() {
-  redirect('/en/docs');
+export default async function HomePage() {
+  const headersList = await headers();
+  const acceptLanguage = headersList.get('accept-language') || '';
+  
+  // Parse the Accept-Language header and find the best match
+  const preferredLang = getPreferredLanguage(acceptLanguage, i18n.languages);
+  
+  redirect(`/${preferredLang}/docs`);
+}
+
+function getPreferredLanguage(acceptLanguage: string, availableLanguages: readonly string[]): string {
+  // Parse Accept-Language header (e.g., "zh-CN,zh;q=0.9,en;q=0.8")
+  const languages = acceptLanguage
+    .split(',')
+    .map(lang => {
+      const parts = lang.trim().split(';');
+      const code = parts[0];
+      const quality = parts[1] ? parseFloat(parts[1].split('=')[1]) : 1.0;
+      return { code, quality };
+    })
+    .sort((a, b) => b.quality - a.quality);
+
+  // Try to find the best match (exact or partial) respecting quality order
+  for (const lang of languages) {
+    // Try exact match first
+    if (availableLanguages.includes(lang.code)) {
+      return lang.code;
+    }
+    
+    // Try partial match (e.g., "zh" matches "zh-CN")
+    const langPrefix = lang.code.split('-')[0].toLowerCase();
+    const match = availableLanguages.find(available => 
+      available.toLowerCase().startsWith(langPrefix)
+    );
+    if (match) {
+      return match;
+    }
+  }
+
+  // Default to the configured default language
+  return i18n.defaultLanguage;
 }

From 29b039c30529c5cbebfaedf6d0d9634605f8724f Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Fri, 16 Jan 2026 10:16:38 +0000
Subject: [PATCH 3/3] Add robust error handling for Accept-Language header
 parsing

Co-authored-by: huangyiirene <7665279+huangyiirene@users.noreply.github.com>
---
 app/page.tsx | 22 ++++++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/app/page.tsx b/app/page.tsx
index 903f940..744c722 100644
--- a/app/page.tsx
+++ b/app/page.tsx
@@ -18,10 +18,28 @@ function getPreferredLanguage(acceptLanguage: string, availableLanguages: readon
     .split(',')
     .map(lang => {
       const parts = lang.trim().split(';');
-      const code = parts[0];
-      const quality = parts[1] ? parseFloat(parts[1].split('=')[1]) : 1.0;
+      const code = parts[0].trim();
+      
+      // Skip empty language codes
+      if (!code) {
+        return null;
+      }
+      
+      // Parse quality value, default to 1.0 if not present or invalid
+      let quality = 1.0;
+      if (parts[1]) {
+        const qPart = parts[1].trim();
+        if (qPart.startsWith('q=')) {
+          const parsedQuality = parseFloat(qPart.substring(2));
+          if (!isNaN(parsedQuality)) {
+            quality = parsedQuality;
+          }
+        }
+      }
+      
       return { code, quality };
     })
+    .filter((lang): lang is { code: string; quality: number } => lang !== null)
     .sort((a, b) => b.quality - a.quality);
 
   // Try to find the best match (exact or partial) respecting quality order