import {
  AngularNodeAppEngine,
  createNodeRequestHandler,
  isMainModule,
  writeResponseToNodeResponse,
} from '@angular/ssr/node';
import { AngularAppEngine } from '@angular/ssr';
import * as http from 'node:http';

// Enable serving prerendered static HTML from disk. Without this flag the
// engine falls back to SSR for every route, ignoring the prerendered output.
AngularAppEngine.ɵallowStaticRouteRender = true;

/**
 * Public routes prerendered at build time (SSG — Static Site Generation).
 * These five routes are compiled to static HTML during `ng build` and
 * served directly from disk at runtime for optimal performance and SEO.
 * The list here mirrors `prerender-routes.txt` and the Prerender entries
 * in `src/app/app.server.routes.ts`.
 */
export const PRERENDERED_ROUTES: readonly string[] = [
  '/',
  '/about',
  '/schedule',
  '/events',
  '/contact',
];

/**
 * Normalise a request pathname and check against prerendered routes.
 * Handles both bare paths (`/about`) and trailing-slash variants (`/about/`).
 */
export function isPrerenderedRoute(url: string): boolean {
  const pathname = new URL(url, 'http://localhost').pathname;
  const normalised = pathname.endsWith('/') && pathname !== '/'
    ? pathname.slice(0, -1)
    : pathname;
  return PRERENDERED_ROUTES.includes(normalised);
}

/**
 * Lazily instantiate AngularNodeAppEngine so the engine boots only when
 * the first request arrives. The engine handles both prerendered route
 * lookups and on-demand SSR bootstrapping internally.
 */
let appEngine: AngularNodeAppEngine | null = null;
function getEngine(): AngularNodeAppEngine {
  if (!appEngine) {
    appEngine = new AngularNodeAppEngine();
  }
  return appEngine;
}

/**
 * Handle incoming requests using the Angular SSR engine.
 *
 * Prerendered routes (/ , /about, /schedule, /events, /contact) are served
 * as pre-generated static HTML from the build output. All other routes
 * fall back to server-side rendering (SSR) or the fallback 404 handler.
 */
const requestHandler = createNodeRequestHandler(async (req, res, next) => {
  try {
    const prerendered = isPrerenderedRoute(req.url || '/');
    if (prerendered) {
      console.log(`[SSR] Prerendered route: ${req.url}`);
    }

    // AngularNodeAppEngine handles manifest registration internally —
    // no manual bootstrap import needed. For prerendered routes it
    // returns pre-generated static HTML; for SSR routes it bootstraps
    // the Angular app on demand.
    const response = await getEngine().handle(req);

    if (response) {
      await writeResponseToNodeResponse(response, res);
    } else {
      next();
    }
  } catch (error) {
    next(error);
  }
});

export default requestHandler;

if (isMainModule(import.meta.url)) {
  const httpServer = http.createServer();
  httpServer.on('request', async (req: http.IncomingMessage, res: http.ServerResponse) => {
    requestHandler(req, res, () => {
      res.statusCode = 404;
      res.end('Not Found');
    });
  });
  httpServer.listen(4200, () => {
    console.log(`Node SSR server listening on http://localhost:4200`);
  });
}