feat: add message Pub/Sub pattern

server/src/utils/message-pub-sub.ts

@@ -0,0 +1,31 @@
+type Message = {
+    userId: Number,
+    content: string,
+    created_at: Date
+}
+
+type Subscriber = (message: Message) => void
+
+class messagesPubSub {
+    private channels: Record<string, Subscriber[]> = {}
+
+    subscribe(channelId: string, subscriber: Subscriber) {
+        if (!this.channels[channelId]) {
+            this.channels[channelId] = []
+        }
+
+        this.channels[channelId].push(subscriber)
+    }
+
+    publish(channelId: string, message: Message) {
+        if (!this.channels[channelId]) {
+            return;
+        }
+
+        for (const subscriber of this.channels[channelId]) {
+            subscriber(message)
+        }
+    }
+}
+
+export const messageDisplay = new messagesPubSub()