Add pi web POC

src/server/realtime/sessionEventHub.ts

@@ -0,0 +1,22 @@
+import type { WebSocket } from "ws";
+
+export class SessionEventHub {
+  private readonly socketsBySession = new Map<string, Set<WebSocket>>();
+
+  add(sessionId: string, socket: WebSocket): void {
+    let sockets = this.socketsBySession.get(sessionId);
+    if (!sockets) {
+      sockets = new Set();
+      this.socketsBySession.set(sessionId, sockets);
+    }
+    sockets.add(socket);
+    socket.on("close", () => sockets?.delete(socket));
+  }
+
+  publish(sessionId: string, event: unknown): void {
+    const payload = JSON.stringify(event);
+    for (const socket of this.socketsBySession.get(sessionId) ?? []) {
+      if (socket.readyState === socket.OPEN) socket.send(payload);
+    }
+  }
+}