initial

apps/server/src/services/broker.ts

@@ -0,0 +1,38 @@
+export type Frame = Record<string, unknown> & { type: string };
+export type Listener = (frame: Frame) => void;
+
+export interface Broker {
+  publish(sessionId: string, frame: Frame): void;
+  subscribe(sessionId: string, listener: Listener): () => void;
+}
+
+export function createBroker(): Broker {
+  const topics = new Map<string, Set<Listener>>();
+  return {
+    publish(sessionId, frame) {
+      const set = topics.get(sessionId);
+      if (!set) return;
+      for (const listener of set) {
+        try {
+          listener(frame);
+        } catch {
+          // ignore listener errors so one bad subscriber doesn't break the rest
+        }
+      }
+    },
+    subscribe(sessionId, listener) {
+      let set = topics.get(sessionId);
+      if (!set) {
+        set = new Set();
+        topics.set(sessionId, set);
+      }
+      set.add(listener);
+      return () => {
+        const s = topics.get(sessionId);
+        if (!s) return;
+        s.delete(listener);
+        if (s.size === 0) topics.delete(sessionId);
+      };
+    },
+  };
+}