UX mejorada

backend/server.js

@@ -15,6 +15,29 @@ const client = new MongoClient(uri);
 
 let db;
 let amigosCollection;
+const clients = new Set();
+
+function sseHeaders(res) {
+  res.setHeader('Content-Type', 'text/event-stream');
+  res.setHeader('Cache-Control', 'no-cache');
+  res.setHeader('Connection', 'keep-alive');
+  res.flushHeaders && res.flushHeaders();
+}
+
+function sendEvent(res, event, data) {
+  if (event) res.write(`event: ${event}\n`);
+  res.write(`data: ${JSON.stringify(data)}\n\n`);
+}
+
+function broadcast(event, data) {
+  for (const res of clients) {
+    try {
+      sendEvent(res, event, data);
+    } catch (_) {
+      // client may be closed
+    }
+  }
+}
 
 // Connect to MongoDB
 async function connectDB() {
@@ -62,14 +85,35 @@ app.post('/api/amigos', async (req, res) => {
       id: result.insertedId,
       nombre 
     });
+
+    // SSE notify
+    broadcast('amigoAdded', { id: result.insertedId, nombre });
   } catch (error) {
     res.status(500).json({ error: error.message });
   }
 });
 
+// SSE endpoint
+app.get('/api/events', async (req, res) => {
+  sseHeaders(res);
+  clients.add(res);
+
+  try {
+    const amigos = await amigosCollection.find({}).toArray();
+    sendEvent(res, 'init', { amigos });
+  } catch (_) {
+    sendEvent(res, 'init', { amigos: [] });
+  }
+
+  req.on('close', () => {
+    clients.delete(res);
+    try { res.end(); } catch (_) {}
+  });
+});
+
 // Start server
 connectDB().then(() => {
   app.listen(PORT, () => {
     console.log(`Server running on http://localhost:${PORT}`);
   });
-});
+});