mcp-hub-003: Client SSE transport and message relay

src/routes/mcp-proxy.js

@@ -0,0 +1,51 @@
+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);
+
+  return res.status(202).json({ status: 'accepted' });
+});
+
+module.exports = router;
+module.exports.sessions = sessions;