feat: implement real-time event handling and SSE support; add event publishing and subscription mechanisms

app/game-api/src/realtime/eventHub.ts

@@ -0,0 +1,64 @@
+import type { RedisConnector } from '@sammo-ts/infra';
+import type { RealtimeEvent } from '@sammo-ts/common';
+
+export type RealtimeListener = (event: RealtimeEvent) => void;
+
+export const parseRealtimeEvent = (message: string): RealtimeEvent | null => {
+    if (!message) {
+        return null;
+    }
+    try {
+        const parsed = JSON.parse(message) as RealtimeEvent;
+        if (!parsed || typeof parsed !== 'object') {
+            return null;
+        }
+        if (typeof parsed.type !== 'string') {
+            return null;
+        }
+        return parsed;
+    } catch {
+        return null;
+    }
+};
+
+// Redis pub/sub 이벤트를 SSE 구독자에게 전달하는 중계 허브.
+export class RedisRealtimeEventHub {
+    private readonly listeners = new Set<RealtimeListener>();
+    private subscribed = false;
+
+    constructor(
+        private readonly redis: RedisConnector['client'],
+        private readonly channel: string
+    ) {}
+
+    async start(): Promise<void> {
+        if (this.subscribed) {
+            return;
+        }
+        await this.redis.subscribe(this.channel, (message) => {
+            const event = parseRealtimeEvent(message);
+            if (!event) {
+                return;
+            }
+            for (const listener of this.listeners) {
+                listener(event);
+            }
+        });
+        this.subscribed = true;
+    }
+
+    subscribe(listener: RealtimeListener): () => void {
+        this.listeners.add(listener);
+        return () => {
+            this.listeners.delete(listener);
+        };
+    }
+
+    async stop(): Promise<void> {
+        if (this.subscribed) {
+            await this.redis.unsubscribe(this.channel);
+            this.subscribed = false;
+        }
+        await this.redis.quit();
+    }
+}