feat: AI client user-agent detection for automatic markdown serving

src/middleware.ts

@@ -19,12 +19,110 @@ export const config = {
 
 // This function can be marked `async` if using `await` inside
 export function middleware(request: NextRequest) {
+  // Check for AI/LLM clients and redirect to markdown if appropriate
+  const markdownRedirect = handleAIClientRedirect(request);
+  if (markdownRedirect) {
+    return markdownRedirect;
+  }
+
   return handleRedirects(request);
 }
 
 // don't send Permanent Redirects (301) in dev mode - it gets cached for "localhost" by the browser
 const redirectStatusCode = process.env.NODE_ENV === 'development' ? 302 : 301;
 
+/**
+ * Detects if the user agent belongs to an AI/LLM tool or development environment
+ * that would benefit from markdown format
+ */
+function isAIOrDevTool(userAgent: string): boolean {
+  const patterns = [
+    /claude/i, // Claude Desktop/Code
+    /cursor/i, // Cursor IDE
+    /copilot/i, // GitHub Copilot
+    /chatgpt/i, // ChatGPT
+    /openai/i, // OpenAI tools
+    /anthropic/i, // Anthropic tools
+    /vscode/i, // VS Code extensions
+    /intellij/i, // IntelliJ plugins
+    /sublime/i, // Sublime Text plugins
+    /got/i, // Got HTTP library (sindresorhus/got)
+    // Add more patterns as needed
+  ];
+
+  return patterns.some(pattern => pattern.test(userAgent));
+}
+
+/**
+ * Handles redirection to markdown versions for AI/LLM clients
+ */
+const handleAIClientRedirect = (request: NextRequest) => {
+  const userAgent = request.headers.get('user-agent') || '';
+  const url = request.nextUrl;
+
+  // Determine if this will be served as markdown
+  const forceMarkdown = url.searchParams.get('format') === 'md';
+  const isAIClient = isAIOrDevTool(userAgent);
+  const willServeMarkdown =
+    (isAIClient || forceMarkdown) && !url.pathname.endsWith('.md');
+
+  // Log user agent for debugging (only for non-static assets)
+  if (
+    !url.pathname.startsWith('/_next/') &&
+    !url.pathname.includes('.') &&
+    !url.pathname.startsWith('/api/')
+  ) {
+    const contentType = willServeMarkdown ? '📄 MARKDOWN' : '🌐 HTML';
+    console.log(
+      `[Middleware] ${url.pathname} - ${contentType} - User-Agent: ${userAgent}`
+    );
+  }
+
+  // Skip if already requesting a markdown file
+  if (url.pathname.endsWith('.md')) {
+    return undefined;
+  }
+
+  // Skip API routes and static assets (should already be filtered by matcher)
+  if (
+    url.pathname.startsWith('/api/') ||
+    url.pathname.startsWith('/_next/') ||
+    /\.(js|json|png|jpg|jpeg|gif|ico|pdf|css|woff|woff2|ttf|map|xml|txt|zip|svg)$/i.test(
+      url.pathname
+    )
+  ) {
+    return undefined;
+  }
+
+  // Check for AI client detection
+
+  if (isAIClient || forceMarkdown) {
+    // Log the redirect for debugging
+    console.log(
+      `[Middleware] Redirecting to markdown: ${isAIClient ? 'AI client detected' : 'Manual format=md'}`
+    );
+
+    // Create new URL with .md extension
+    const newUrl = url.clone();
+    // Handle root path and ensure proper .md extension
+    let pathname = url.pathname === '/' ? '/index' : url.pathname;
+    // Remove all trailing slashes if present, then add .md
+    pathname = pathname.replace(/\/+$/, '') + '.md';
+    newUrl.pathname = pathname;
+
+    // Clean up the format query parameter if it was used
+    if (forceMarkdown) {
+      newUrl.searchParams.delete('format');
+    }
+
+    return NextResponse.redirect(newUrl, {
+      status: redirectStatusCode,
+    });
+  }
+
+  return undefined;
+};
+
 const handleRedirects = (request: NextRequest) => {
   const urlPath = request.nextUrl.pathname;