// Production static-file server for the built SPA, run by Bun (replaces nginx).
// Serves apps/frontend/dist and reverse-proxies backend routes so the
// session cookie stays first-party. Dev still uses Vite (see vite.config.ts).

const PORT = Number(process.env.PORT ?? 8080);
const BACKEND_URL = process.env.BACKEND_URL ?? "http://localhost:3001";
const DIST = "./dist";

function isProxied(pathname: string): boolean {
  return (
    pathname === "/health" ||
    pathname.startsWith("/auth") ||
    pathname.startsWith("/api") ||
    pathname.startsWith("/internal")
  );
}

// Forward the request to the backend, preserving method/headers/body/cookies.
async function proxy(req: Request, url: URL): Promise<Response> {
  const target = new URL(url.pathname + url.search, BACKEND_URL);
  const headers = new Headers(req.headers);
  // Let fetch set Host from the target URL (Cloud Run routes by Host).
  headers.delete("host");
  headers.set("x-forwarded-host", url.host);
  headers.set("x-forwarded-proto", url.protocol.replace(":", ""));

  const init: RequestInit = { method: req.method, headers, redirect: "manual" };
  if (req.method !== "GET" && req.method !== "HEAD") {
    init.body = await req.arrayBuffer();
  }
  return fetch(target, init);
}

async function serveStatic(url: URL): Promise<Response> {
  const pathname = url.pathname === "/" ? "/index.html" : url.pathname;
  const file = Bun.file(`${DIST}${pathname}`);
  if (await file.exists()) {
    const headers: Record<string, string> =
      pathname.startsWith("/assets/")
        ? { "Cache-Control": "public, max-age=31536000, immutable" }
        : { "Cache-Control": "no-cache" };
    return new Response(file, { headers });
  }
  // SPA fallback: serve index.html for client-side routes.
  return new Response(Bun.file(`${DIST}/index.html`), { headers: { "Cache-Control": "no-cache" } });
}

Bun.serve({
  port: PORT,
  fetch(req) {
    const url = new URL(req.url);
    return isProxied(url.pathname) ? proxy(req, url) : serveStatic(url);
  },
});

console.log(`cerebrus-frontend serving on :${PORT} (proxy backend routes -> ${BACKEND_URL})`);