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

/**
 * Lazily instantiate AngularNodeAppEngine so the engine boots only when
 * the first request arrives. All routes use RenderMode.Server — every
 * request triggers on-demand SSR that fetches fresh API data before rendering.
 */
let appEngine: AngularNodeAppEngine | null = null;
function getEngine(): AngularNodeAppEngine {
  if (!appEngine) {
    appEngine = new AngularNodeAppEngine();
  }
  return appEngine;
}

/**
 * Handle incoming requests using the Angular SSR engine.
 * Every request is rendered on the server with fresh data from the API.
 */
const requestHandler = createNodeRequestHandler(async (req, res, next) => {
  try {
    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`);
  });
}