make clients of sse service observable

dist/sse.js

@@ -1,13 +1,35 @@
 import { logInfo } from "./logger.js";
 export class SseService {
     clients = new Map();
+    clientChangeCallbacks = [];
+    onClientChange(callback) {
+        this.clientChangeCallbacks.push(callback);
+        return () => {
+            this.clientChangeCallbacks = this.clientChangeCallbacks.filter((cb) => cb !== callback);
+        };
+    }
+    emitClientChange(event) {
+        for (const callback of this.clientChangeCallbacks) {
+            callback(event);
+        }
+    }
     addClient(client) {
         this.clients.set(client.id, client);
         logInfo(`SSE client connected: ${client.id}. Total clients: ${this.clients.size}`);
+        this.emitClientChange({
+            type: "add",
+            clientId: client.id,
+            clientCount: this.clients.size,
+        });
     }
     removeClient(clientId) {
         this.clients.delete(clientId);
         logInfo(`SSE client disconnected: ${clientId}. Total clients: ${this.clients.size}`);
+        this.emitClientChange({
+            type: "remove",
+            clientId,
+            clientCount: this.clients.size,
+        });
     }
     notifyClients(event) {
         for (const client of this.clients.values()) {