Initial Commit

server/sse.js

@@ -0,0 +1,39 @@
+'use strict';
+
+const clients = new Set();
+
+/**
+ * Register an SSE response and keep the connection alive.
+ */
+function addClient(res) {
+  res.setHeader('Content-Type', 'text/event-stream');
+  res.setHeader('Cache-Control', 'no-cache');
+  res.setHeader('Connection', 'keep-alive');
+  res.flushHeaders();
+
+  // Send an immediate heartbeat so the browser knows the stream is live
+  res.write('data: {"type":"connected"}\n\n');
+
+  const heartbeat = setInterval(() => {
+    res.write(': heartbeat\n\n');
+  }, 20000);
+
+  clients.add(res);
+
+  res.on('close', () => {
+    clearInterval(heartbeat);
+    clients.delete(res);
+  });
+}
+
+/**
+ * Push an event to all connected SSE clients.
+ */
+function broadcast(data) {
+  const payload = `data: ${JSON.stringify(data)}\n\n`;
+  for (const client of clients) {
+    client.write(payload);
+  }
+}
+
+module.exports = { addClient, broadcast };