middleware.ts

import { rewrite, next } from '@vercel/edge';
import { pathInfo, buildTrackingPayload } from './lib/llms-tracking';

// PostHog project public key — same as docusaurus.config.js. Public, not a secret.
const POSTHOG_KEY = 'phc_AscFTQ876SsPAVMgxMmLn0EIpxdcRRq0XmJWnpG1SHL';

export const config = {
  matcher: [
    // Clean URLs — for Accept: text/markdown content negotiation.
    '/((?!.*\\.).*)',
    // Index files generated by @signalwire/docusaurus-plugin-llms-txt.
    '/llms.txt',
    '/llms-full.txt',
    // Per-page markdown mirrors; exclude auto-generated SDK pages.
    '/((?!sdk/).*)\\.md',
  ],
};

interface MiddlewareContext {
  waitUntil: (promise: Promise<unknown>) => void;
}

export default async function middleware(request: Request, context: MiddlewareContext) {
  const url = new URL(request.url);
  const pathname = url.pathname;
  const accept = request.headers.get('accept') ?? '';

  const info = pathInfo(pathname, accept);

  // Tracking — production only. Never blocks the response.
  if (process.env.VERCEL_ENV === 'production' && info.kind !== 'ignored') {
    const ua = request.headers.get('user-agent') ?? '';
    const referrer = request.headers.get('referer') ?? '';
    const ip = request.headers.get('x-forwarded-for')?.split(',')[0]?.trim() ?? '';

    context.waitUntil(
      buildTrackingPayload({
        trackedPath: info.trackedPath,
        fileType: info.fileType,
        userAgent: ua,
        referrer,
        ip,
        posthogKey: POSTHOG_KEY,
      })
        .then((payload) =>
          fetch('https://app.posthog.com/capture/', {
            method: 'POST',
            headers: { 'Content-Type': 'application/json' },
            body: JSON.stringify(payload),
          }),
        )
        .catch(() => {
          // Silent — tracking errors must never break responses.
        }),
    );
  }

  // Markdown content-negotiation rewrite — preserved from prior middleware.
  if (info.kind === 'markdown-negotiate') {
    url.pathname = info.trackedPath;
    return rewrite(url);
  }

  return next();
}