Added SSE function and add readAt for notification

src/lib/notification.ts

@@ -0,0 +1,52 @@
+type Controller = ReadableStreamDefaultController;
+
+const userClients = new Map<string, Set<Controller>>();
+
+/**
+ * Thêm connection cho user
+ */
+export function addClient(userId: string, controller: Controller) {
+  if (!userClients.has(userId)) {
+    userClients.set(userId, new Set());
+  }
+
+  userClients.get(userId)!.add(controller);
+}
+
+/**
+ * Xoá connection khi tab đóng
+ */
+export function removeClient(userId: string, controller: Controller) {
+  const controllers = userClients.get(userId);
+  if (!controllers) return;
+
+  controllers.delete(controller);
+
+  // nếu user không còn tab nào mở thì xoá luôn
+  if (controllers.size === 0) {
+    userClients.delete(userId);
+  }
+}
+
+/**
+ * Gửi notification cho 1 user
+ */
+export function sendToUser(userId: string, data: any) {
+  const controllers = userClients.get(userId);
+  if (!controllers) return;
+
+  for (const controller of controllers) {
+    controller.enqueue(`data: ${JSON.stringify(data)}\n\n`);
+  }
+}
+
+/**
+ * Gửi cho tất cả user
+ */
+export function broadcast(data: any) {
+  for (const controllers of userClients.values()) {
+    for (const controller of controllers) {
+      controller.enqueue(`data: ${JSON.stringify(data)}\n\n`);
+    }
+  }
+}