import 'dotenv/config';
import http from 'http';
import https from 'https';

const TARGET = process.env.PROXY_API_TARGET;
const PORT = process.env.PROXY_API_PORT;
const LOCAL_ORIGIN = process.env.PROXY_LOCAL_ORIGIN;
const PROD_ORIGIN = process.env.PROXY_PROD_ORIGIN;

if (!TARGET) throw new Error('PROXY_API_TARGET environment variable is required');
if (!PORT) throw new Error('PROXY_API_PORT environment variable is required');
if (!LOCAL_ORIGIN) throw new Error('PROXY_LOCAL_ORIGIN environment variable is required');
if (!PROD_ORIGIN) throw new Error('PROXY_PROD_ORIGIN environment variable is required');

const parsedPort = parseInt(PORT, 10);

const server = http.createServer((req, res) => {
  // Handle preflight OPTIONS requests
  if (req.method === 'OPTIONS') {
    res.setHeader('Access-Control-Allow-Origin', LOCAL_ORIGIN);
    res.setHeader('Access-Control-Allow-Credentials', 'true');
    res.setHeader('Access-Control-Allow-Methods', 'GET, POST, PUT, DELETE, OPTIONS, PATCH');
    res.setHeader('Access-Control-Allow-Headers', 'Content-Type, Authorization, X-Timezone, X-Locale');
    res.writeHead(204);
    res.end();
    return;
  }

  // Rewrite origin to match production so backend CORS accepts it
  const headers = { ...req.headers, host: TARGET };
  if (headers.origin === LOCAL_ORIGIN) {
    headers.origin = PROD_ORIGIN;
  }

  const options = {
    hostname: TARGET,
    port: 443,
    path: req.url,
    method: req.method,
    headers,
  };

  const proxyReq = https.request(options, (proxyRes) => {
    // Merge CORS headers with response headers
    const headers = { ...proxyRes.headers };
    headers['access-control-allow-origin'] = LOCAL_ORIGIN;
    headers['access-control-allow-credentials'] = 'true';

    res.writeHead(proxyRes.statusCode, headers);
    proxyRes.pipe(res);
  });

  proxyReq.on('error', (err) => {
    console.error('Proxy error:', err);
    res.writeHead(500);
    res.end('Proxy error');
  });

  req.pipe(proxyReq);
});

// Handle WebSocket upgrades for Socket.IO
server.on('upgrade', (req, socket, head) => {
  // Rewrite origin to match production so backend CORS accepts it
  const headers = { ...req.headers, host: TARGET };
  if (headers.origin === LOCAL_ORIGIN) {
    headers.origin = PROD_ORIGIN;
  }

  const options = {
    hostname: TARGET,
    port: 443,
    path: req.url,
    method: 'GET',
    headers,
  };

  const proxyReq = https.request(options);

  proxyReq.on('upgrade', (proxyRes, proxySocket, proxyHead) => {
    let response = 'HTTP/1.1 101 Switching Protocols\r\n' +
      'Upgrade: websocket\r\n' +
      'Connection: Upgrade\r\n' +
      `Sec-WebSocket-Accept: ${proxyRes.headers['sec-websocket-accept']}\r\n`;

    // Forward compression extension if backend negotiated it
    if (proxyRes.headers['sec-websocket-extensions']) {
      response += `Sec-WebSocket-Extensions: ${proxyRes.headers['sec-websocket-extensions']}\r\n`;
    }

    response += '\r\n';
    socket.write(response);

    proxySocket.pipe(socket);
    socket.pipe(proxySocket);
  });

  proxyReq.on('error', (err) => {
    console.error('WebSocket proxy error:', err);
    socket.end();
  });

  proxyReq.end();
});

server.listen(parsedPort, () => {
  console.log(`API Proxy running: localhost:${parsedPort} -> ${TARGET} (HTTP + WebSocket)`);
});