feat(core-realtime): InMemoryRealtimeBroadcaster (test/dev impl)

packages/core-realtime/src/in-memory-realtime-broadcaster.ts

@@ -0,0 +1,28 @@
+import type { z } from "zod";
+import type { IRealtimeBroadcaster } from "./realtime-broadcaster.interface";
+import type { RealtimeChannelDescriptor } from "./realtime-channel";
+
+type Listener<T> = (payload: T) => Promise<void> | void;
+
+export class InMemoryRealtimeBroadcaster implements IRealtimeBroadcaster {
+  private readonly listeners = new Map<string, Listener<unknown>[]>();
+
+  async broadcast<T>(
+    descriptor: RealtimeChannelDescriptor<string, z.ZodType<T>>,
+    payload: T,
+  ): Promise<void> {
+    descriptor.schema.parse(payload);
+    const arr = this.listeners.get(descriptor.name) ?? [];
+    for (const l of arr) await l(payload);
+  }
+
+  // Test-friendly: lets unit tests subscribe directly without a Socket.IO server.
+  subscribe<T>(
+    descriptor: RealtimeChannelDescriptor<string, z.ZodType<T>>,
+    listener: Listener<T>,
+  ): void {
+    const arr = this.listeners.get(descriptor.name) ?? [];
+    arr.push(listener as Listener<unknown>);
+    this.listeners.set(descriptor.name, arr);
+  }
+}