const { Router } = require('express');
const { v4: uuidv4 } = require('uuid');
const registry = require('../backend-registry');
const relay = require('../relay');

const router = Router();
const sessions = new Map();

router.get('/:serviceId/sse', (req, res) => {
  const { serviceId } = req.params;

  if (!registry.get(serviceId)) {
    return res.status(502).json({ error: 'backend not connected' });
  }

  res.setHeader('Content-Type', 'text/event-stream');
  res.setHeader('Cache-Control', 'no-cache');
  res.setHeader('Connection', 'keep-alive');
  res.flushHeaders();

  const clientSessionId = uuidv4();
  sessions.set(clientSessionId, { res, serviceId });

  res.write('event: endpoint\ndata: /' + serviceId + '/message?sessionId=' + clientSessionId + '\n\n');

  req.on('close', () => {
    sessions.delete(clientSessionId);
    console.log('[sse] client disconnected: ' + clientSessionId + ' (' + serviceId + ')');
  });
});

router.post('/:serviceId/message', (req, res) => {
  const { serviceId } = req.params;
  const { sessionId } = req.query;

  const session = sessions.get(sessionId);
  if (!session) {
    return res.status(404).json({ error: 'session not found' });
  }

  if (!registry.get(serviceId)) {
    return res.status(502).json({ error: 'backend not connected' });
  }

  relay.sendToBackend(serviceId, req.body, sessionId, sessions);

  return res.status(202).json({ status: 'accepted' });
});

module.exports = router;
module.exports.sessions = sessions;