proxy.ts

import { NextRequest, NextResponse } from 'next/server';

// Map routes to their API markdown endpoints
const MARKDOWN_ROUTES: Record<string, string> = {
  '/specification': 'specification',
  '/deployment': 'deployment',
  '/migration': 'migration',
  '/threat-model': 'threat-model',
  '/ai-access': 'ai-access',
  '/faq': 'faq',
  '/resumen': 'resumen', // Spanish summary (bonus)
  '/getting-started': 'getting-started',
  '/schemas': 'schemas',
  '/test-vectors': 'test-vectors',
  '/reference-impl': 'reference-impl',
  '/aap-vs-web-bot-auth': 'aap-vs-web-bot-auth',
};

export function proxy(request: NextRequest) {
  const { pathname } = request.nextUrl;

  // Handle direct .md URLs (e.g., /specification.md)
  if (pathname.endsWith('.md')) {
    const baseRoute = pathname.replace(/\.md$/, '');
    const slug = MARKDOWN_ROUTES[baseRoute];

    if (slug) {
      // Rewrite to API route that serves markdown
      const apiUrl = new URL(`/api/markdown/${slug}`, request.url);
      return NextResponse.rewrite(apiUrl);
    }
  }

  // Check if this route has a markdown version
  const slug = MARKDOWN_ROUTES[pathname];
  if (!slug) {
    return NextResponse.next();
  }

  // Check if client accepts markdown via Accept header
  const acceptHeader = request.headers.get('accept') || '';
  const acceptsMarkdown = acceptHeader.includes('text/markdown') ||
                          acceptHeader.includes('text/x-markdown');

  if (acceptsMarkdown) {
    // Rewrite to API route that serves markdown
    const apiUrl = new URL(`/api/markdown/${slug}`, request.url);
    const response = NextResponse.rewrite(apiUrl);

    // Add Vary header for proper caching
    response.headers.set('Vary', 'Accept');

    // Add Link header pointing to .md URL
    response.headers.set(
      'Link',
      `<${pathname}.md>; rel="alternate"; type="text/markdown"`
    );

    return response;
  }

  // For regular browsers, continue with normal HTML response
  // but add Link header to advertise markdown availability
  const response = NextResponse.next();
  response.headers.set(
    'Link',
    `<${pathname}.md>; rel="alternate"; type="text/markdown"`
  );

  return response;
}

export const config = {
  matcher: [
    '/specification',
    '/specification.md',
    '/deployment',
    '/deployment.md',
    '/migration',
    '/migration.md',
    '/threat-model',
    '/threat-model.md',
    '/ai-access',
    '/ai-access.md',
    '/faq',
    '/faq.md',
    '/resumen',
    '/resumen.md',
    '/getting-started',
    '/getting-started.md',
    '/schemas',
    '/schemas.md',
    '/test-vectors',
    '/test-vectors.md',
    '/reference-impl',
    '/reference-impl.md',
    '/aap-vs-web-bot-auth',
    '/aap-vs-web-bot-auth.md',
  ],
};