/**
 * Custom Next.js standalone server.
 * Proxies /api/* requests to BACKEND_URL (resolved at RUNTIME, not build time).
 * This is needed because next.config.ts rewrites are baked in at build time.
 */
const { createServer } = require("http");
const { parse } = require("url");
const next = require("next");

const port = parseInt(process.env.PORT || "3000", 10);
const hostname = process.env.HOSTNAME || "0.0.0.0";
const dev = process.env.NODE_ENV !== "production";

const backendUrl = (process.env.BACKEND_URL || "http://127.0.0.1:8000").replace(/\/$/, "");

const app = next({ dev, hostname, port });
const handle = app.getRequestHandler();

app.prepare().then(() => {
  createServer(async (req, res) => {
    try {
      const parsedUrl = parse(req.url, true);
      const { pathname } = parsedUrl;

      // Proxy /api/* to backend
      if (pathname.startsWith("/api/")) {
        const http = require("http");
        const targetUrl = new URL(req.url, backendUrl);

        const proxyReq = http.request(
          targetUrl,
          {
            method: req.method,
            headers: {
              ...req.headers,
              host: targetUrl.host,
            },
          },
          (proxyRes) => {
            res.writeHead(proxyRes.statusCode, proxyRes.headers);
            proxyRes.pipe(res, { end: true });
          }
        );

        proxyReq.on("error", (err) => {
          console.error(`Proxy error for ${req.url}:`, err.message);
          res.writeHead(502);
          res.end("Bad Gateway");
        });

        req.pipe(proxyReq, { end: true });
        return;
      }

      // All other requests -> Next.js
      await handle(req, res, parsedUrl);
    } catch (err) {
      console.error("Error occurred handling", req.url, err);
      res.writeHead(500);
      res.end("internal server error");
    }
  }).listen(port, hostname, () => {
    console.log(`> Ready on http://${hostname}:${port}`);
    console.log(`> API proxy: ${backendUrl}`);
  });
});
