Implement App/User Listener (#5080)

* Finish App Listener

Used the `subscribe` and `unsubscribe` methods to finish the app listener implementation.

* Implement user listeners

packages/realm/src/app-services/App.ts

@@ -40,6 +40,8 @@ export type AppConfiguration = {
 
 export type AppChangeCallback = () => void;
 
+type AppListenerToken = binding.AppSubscriptionToken;
+
 // TODO: Ensure this doesn't leak
 const appByUserId = new Map<string, App>();
 
@@ -79,12 +81,12 @@ export class App {
 
   public userAgent = `RealmJS/${App.SDK_VERSION} (${App.PLATFORM_CONTEXT}, ${App.PLATFORM_OS}, v${App.PLATFORM_VERSION})`;
 
-  private listeners = new Listeners<AppChangeCallback, unknown>({
-    register() {
-      throw new Error("Not yet implemented");
+  private listeners = new Listeners<AppChangeCallback, AppListenerToken>({
+    register: (callback: () => void): AppListenerToken => {
+      return this.internal.subscribe(callback);
     },
-    unregister() {
-      throw new Error("Not yet implemented");
+    unregister: (token) => {
+      this.internal.unsubscribe(token);
     },
   });
 

packages/realm/src/app-services/User.ts

@@ -23,6 +23,7 @@ import {
   DefaultFunctionsFactory,
   DefaultObject,
   DefaultUserProfileData,
+  Listeners,
   ProviderType,
   binding,
   isProviderType,
@@ -57,6 +58,7 @@ export interface UserIdentity {
   providerType: ProviderType;
 }
 
+type UserListenerToken = binding.SyncUserSubscriptionToken;
 export class User<
   FunctionsFactoryType = DefaultFunctionsFactory,
   CustomDataType = DefaultObject,
@@ -68,6 +70,15 @@ export class User<
   /** @internal */
   public internal: binding.SyncUser;
 
+  private listeners = new Listeners<UserChangeCallback, UserListenerToken>({
+    register: (callback: () => void): UserListenerToken => {
+      return this.internal.subscribe(callback);
+    },
+    unregister: (token) => {
+      this.internal.unsubscribe(token);
+    },
+  });
+
   /** @internal */
   public static get(internal: binding.SyncUser) {
     // TODO: Use a WeakRef to memoize the SDK object
@@ -253,20 +264,20 @@ export class User<
    * This includes auth token refresh, refresh token refresh, refresh custom user data, and logout.
    */
   addListener(callback: UserChangeCallback): void {
-    throw new Error("Not yet implemented");
+    this.listeners.add(callback);
   }
 
   /**
    * Removes the event listener
    */
   removeListener(callback: UserChangeCallback): void {
-    throw new Error("Not yet implemented");
+    this.listeners.remove(callback);
   }
 
   /**
    * Removes all event listeners
    */
   removeAllListeners(): void {
-    throw new Error("Not yet implemented");
+    this.listeners.removeAll();
   }
 }