Adding a FidListener that propagates fid changes to the clients.

firebase-installations-interop/firebase-installations-interop.gradle

@@ -40,7 +40,8 @@ android {
 
 dependencies {
 	implementation 'com.google.android.gms:play-services-tasks:17.0.0'
+    implementation project(path: ':firebase-annotations')
 
-	compileOnly "com.google.auto.value:auto-value-annotations:1.6.5"
+    compileOnly "com.google.auto.value:auto-value-annotations:1.6.5"
 	annotationProcessor "com.google.auto.value:auto-value:1.6.2"
 }

firebase-installations-interop/src/main/java/com/google/firebase/installations/FirebaseInstallationsApi.java

@@ -16,6 +16,9 @@
 
 import androidx.annotation.NonNull;
 import com.google.android.gms.tasks.Task;
+import com.google.firebase.annotations.DeferredApi;
+import com.google.firebase.installations.internal.FidListener;
+import com.google.firebase.installations.internal.HandleFidListener;
 
 /**
  * This is an interface of {@code FirebaseInstallations} that is only exposed to 2p via component
@@ -51,4 +54,13 @@ public interface FirebaseInstallationsApi {
    */
   @NonNull
   Task<Void> delete();
+
+  /**
+   * Register a listener to receive fid changes.
+   *
+   * @param listener implementation of the {@code FidListener} to handle fid changes.
+   * @hide
+   */
+  @DeferredApi
+  HandleFidListener registerFidListener(@NonNull FidListener listener);
 }

firebase-installations-interop/src/main/java/com/google/firebase/installations/internal/FidListener.java

@@ -0,0 +1,31 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.firebase.installations.internal;
+
+import androidx.annotation.NonNull;
+
+/**
+ * Provides a call-back interface {@link FidListener} that updates on Fid changes.
+ *
+ * @hide
+ */
+public interface FidListener {
+  /**
+   * This method gets invoked when a Fid changes.
+   *
+   * @param fid represents the newly generated installation id.
+   */
+  void onFidChanged(@NonNull String fid);
+}

firebase-installations-interop/src/main/java/com/google/firebase/installations/internal/HandleFidListener.java

@@ -0,0 +1,30 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.firebase.installations.internal;
+
+/**
+ * Interface for un-registering a previously registered listener.
+ *
+ * @hide
+ */
+public interface HandleFidListener {
+
+  /**
+   * Unregisters a previously registered {@link FidListener}.
+   *
+   * @hide
+   */
+  void unregister(FidListener fidListener);
+}

firebase-installations/src/main/java/com/google/firebase/installations/FirebaseInstallations.java

@@ -28,6 +28,8 @@
 import com.google.firebase.heartbeatinfo.HeartBeatInfo;
 import com.google.firebase.inject.Provider;
 import com.google.firebase.installations.FirebaseInstallationsException.Status;
+import com.google.firebase.installations.internal.FidListener;
+import com.google.firebase.installations.internal.HandleFidListener;
 import com.google.firebase.installations.local.IidStore;
 import com.google.firebase.installations.local.PersistedInstallation;
 import com.google.firebase.installations.local.PersistedInstallationEntry;
@@ -37,8 +39,10 @@
 import com.google.firebase.platforminfo.UserAgentPublisher;
 import java.io.IOException;
 import java.util.ArrayList;
+import java.util.HashSet;
 import java.util.Iterator;
 import java.util.List;
+import java.util.Set;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.LinkedBlockingQueue;
 import java.util.concurrent.ThreadFactory;
@@ -72,6 +76,9 @@ public class FirebaseInstallations implements FirebaseInstallationsApi {
   @GuardedBy("this")
   private String cachedFid;
 
+  @GuardedBy("this")
+  private Set<FidListener> fidListeners = new HashSet<>();
+
   @GuardedBy("lock")
   private final List<StateListener> listeners = new ArrayList<>();
 
@@ -271,6 +278,21 @@ public Task<Void> delete() {
     return Tasks.call(backgroundExecutor, this::deleteFirebaseInstallationId);
   }
 
+  /** Register a callback {@link FidListener} to receive fid changes. */
+  @NonNull
+  @Override
+  public synchronized HandleFidListener registerFidListener(@NonNull FidListener listener) {
+    this.fidListeners.add(listener);
+    return new HandleFidListener() {
+      @Override
+      public void unregister(FidListener fidListener) {
+        if (fidListeners.contains(fidListener)) {
+          fidListeners.remove(fidListener);
+        }
+      }
+    };
+  }
+
   private Task<String> addGetIdListener() {
     TaskCompletionSource<String> taskCompletionSource = new TaskCompletionSource<>();
     StateListener l = new GetIdListener(taskCompletionSource);
@@ -356,11 +378,12 @@ private void doNetworkCallIfNecessary(boolean forceRefresh) {
     // There are two possible cleanup steps to perform at this stage: the FID may need to
     // be registered with the server or the FID is registered but we need a fresh authtoken.
     // Registering will also result in a fresh authtoken. Do the appropriate step here.
+    PersistedInstallationEntry updatedPrefs;
     try {
       if (prefs.isErrored() || prefs.isUnregistered()) {
-        prefs = registerFidWithServer(prefs);
+        updatedPrefs = registerFidWithServer(prefs);
       } else if (forceRefresh || utils.isAuthTokenExpired(prefs)) {
-        prefs = fetchAuthTokenFromServer(prefs);
+        updatedPrefs = fetchAuthTokenFromServer(prefs);
       } else {
         // nothing more to do, get out now
         return;
@@ -371,7 +394,12 @@ private void doNetworkCallIfNecessary(boolean forceRefresh) {
     }
 
     // Store the prefs to persist the result of the previous step.
-    insertOrUpdatePrefs(prefs);
+    insertOrUpdatePrefs(updatedPrefs);
+
+    // Update FidListener if a fid has changed.
+    updateFidListener(prefs, updatedPrefs);
+
+    prefs = updatedPrefs;
 
     // Update cachedFID, if FID is successfully REGISTERED and persisted.
     if (prefs.isRegistered()) {
@@ -390,6 +418,17 @@ private void doNetworkCallIfNecessary(boolean forceRefresh) {
     }
   }
 
+  private synchronized void updateFidListener(
+      PersistedInstallationEntry prefs, PersistedInstallationEntry updatedPrefs) {
+    if (fidListeners.size() != 0
+        && !prefs.getFirebaseInstallationId().equals(updatedPrefs.getFirebaseInstallationId())) {
+      // Update all the registered FidListener about fid changes.
+      for (FidListener listener : fidListeners) {
+        listener.onFidChanged(updatedPrefs.getFirebaseInstallationId());
+      }
+    }
+  }
+
   /**
    * Inserting or Updating the prefs. This operation is made cross-process and cross-thread safe by
    * wrapping all the processing first in a java synchronization block and wrapping that in a

firebase-installations/src/test/java/com/google/firebase/installations/FakeFidListener.java

@@ -0,0 +1,31 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.firebase.installations;
+
+import androidx.annotation.NonNull;
+import com.google.firebase.installations.internal.FidListener;
+
+class FakeFidListener implements FidListener {
+  private String currentFid;
+
+  @Override
+  public void onFidChanged(@NonNull String fid) {
+    currentFid = fid;
+  }
+
+  public String getLatestFid() {
+    return currentFid;
+  }
+}

firebase-installations/src/test/java/com/google/firebase/installations/FirebaseInstallationsTest.java

@@ -74,6 +74,7 @@ public class FirebaseInstallationsTest {
   @Mock private RandomFidGenerator mockFidGenerator;
 
   public static final String TEST_FID_1 = "cccccccccccccccccccccc";
+  public static final String TEST_FID_2 = "dccccccccccccccccccccd";
 
   public static final String TEST_PROJECT_ID = "777777777777";
 
@@ -453,6 +454,40 @@ public void testReadToken_withJsonformatting() {
     assertThat(iidStore.readToken(), equalTo("thetoken"));
   }
 
+  @Test
+  public void testFidListener_fidChanged_successful() throws Exception {
+    when(mockIidStore.readIid()).thenReturn(null);
+    when(mockIidStore.readToken()).thenReturn(null);
+    when(mockBackend.createFirebaseInstallation(
+            anyString(), anyString(), anyString(), anyString(), any()))
+        .thenReturn(
+            TEST_INSTALLATION_RESPONSE
+                .toBuilder()
+                .setUri("/projects/" + TEST_PROJECT_ID + "/installations/" + TEST_FID_2)
+                .setFid(TEST_FID_2)
+                .build());
+
+    FakeFidListener fidListener = new FakeFidListener();
+    // Register the FidListener
+    firebaseInstallations.registerFidListener(fidListener);
+
+    // Do the actual getId() call under test.
+    // Confirm both that it returns the expected ID, as does reading the prefs from storage.
+    TestOnCompleteListener<String> onCompleteListener = new TestOnCompleteListener<>();
+    Task<String> task = firebaseInstallations.getId();
+    task.addOnCompleteListener(executor, onCompleteListener);
+    String fid = onCompleteListener.await();
+    assertWithMessage("getId Task failed.").that(fid).isEqualTo(TEST_FID_1);
+
+    // Waiting for Task that registers FID on the FIS Servers
+    executor.awaitTermination(500, TimeUnit.MILLISECONDS);
+    PersistedInstallationEntry entry = persistedInstallation.readPersistedInstallationEntryValue();
+    assertThat(entry.getFirebaseInstallationId(), equalTo(TEST_FID_2));
+
+    // Verify FidListener receives fid changes.
+    assertThat(fidListener.getLatestFid(), equalTo(TEST_FID_2));
+  }
+
   @Test
   public void testGetId_migrateIid_successful() throws Exception {
     when(mockIidStore.readIid()).thenReturn(TEST_INSTANCE_ID_1);