FID delete() implementation.

firebase-installations/src/androidTest/java/com/google/firebase/installations/FirebaseInstallationsInstrumentedTest.java

@@ -32,6 +32,9 @@
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.ArgumentMatchers.anyString;
 import static org.mockito.Mockito.doAnswer;
+import static org.mockito.Mockito.doNothing;
+import static org.mockito.Mockito.doThrow;
+import static org.mockito.Mockito.never;
 import static org.mockito.Mockito.times;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
@@ -163,6 +166,16 @@ public void setUp() throws FirebaseInstallationServiceException {
     when(persistedFidReturnsError.readPersistedFidEntryValue()).thenReturn(null);
     when(mockUtils.createRandomFid()).thenReturn(TEST_FID_1);
     when(mockClock.currentTimeMillis()).thenReturn(TEST_CREATION_TIMESTAMP_1);
+    // Mocks success on FIS deletion
+    doNothing()
+        .when(backendClientReturnsOk)
+        .deleteFirebaseInstallation(anyString(), anyString(), anyString(), anyString());
+    // Mocks server error on FIS deletion
+    doThrow(
+            new FirebaseInstallationServiceException(
+                "Server Error", FirebaseInstallationServiceException.Status.SERVER_ERROR))
+        .when(backendClientReturnsError)
+        .deleteFirebaseInstallation(anyString(), anyString(), anyString(), anyString());
   }
 
   @After
@@ -483,4 +496,77 @@ public void testGetAuthToken_multipleCallsForceRefresh_fetchedNewTokenTwice() th
     verify(backendClientReturnsOk, times(2))
         .generateAuthToken(TEST_API_KEY, TEST_FID_1, TEST_PROJECT_ID, TEST_REFRESH_TOKEN);
   }
+
+  @Test
+  public void testDelete_registeredFID_successful() throws Exception {
+    // Update local storage with a registered fid entry
+    persistedFid.insertOrUpdatePersistedFidEntry(REGISTERED_FID_ENTRY);
+    FirebaseInstallations firebaseInstallations =
+        new FirebaseInstallations(
+            mockClock, executor, firebaseApp, backendClientReturnsOk, persistedFid, mockUtils);
+
+    Tasks.await(firebaseInstallations.delete());
+
+    PersistedFidEntry entryValue = persistedFid.readPersistedFidEntryValue();
+    assertWithMessage("Persisted Fid Entry is not null.").that(entryValue).isNull();
+    verify(backendClientReturnsOk, times(1))
+        .deleteFirebaseInstallation(TEST_API_KEY, TEST_FID_1, TEST_PROJECT_ID, TEST_REFRESH_TOKEN);
+  }
+
+  @Test
+  public void testDelete_unregisteredFID_successful() throws Exception {
+    // Update local storage with a unregistered fid entry
+    persistedFid.insertOrUpdatePersistedFidEntry(UNREGISTERED_FID_ENTRY);
+    FirebaseInstallations firebaseInstallations =
+        new FirebaseInstallations(
+            mockClock, executor, firebaseApp, backendClientReturnsOk, persistedFid, mockUtils);
+
+    Tasks.await(firebaseInstallations.delete());
+
+    PersistedFidEntry entryValue = persistedFid.readPersistedFidEntryValue();
+    assertWithMessage("Persisted Fid Entry is not null.").that(entryValue).isNull();
+    verify(backendClientReturnsOk, never())
+        .deleteFirebaseInstallation(TEST_API_KEY, TEST_FID_1, TEST_PROJECT_ID, TEST_REFRESH_TOKEN);
+  }
+
+  @Test
+  public void testDelete_emptyPersistedFidEntry_successful() throws Exception {
+    FirebaseInstallations firebaseInstallations =
+        new FirebaseInstallations(
+            mockClock, executor, firebaseApp, backendClientReturnsOk, persistedFid, mockUtils);
+
+    Tasks.await(firebaseInstallations.delete());
+
+    PersistedFidEntry entryValue = persistedFid.readPersistedFidEntryValue();
+    assertWithMessage("Persisted Fid Entry is not null.").that(entryValue).isNull();
+    verify(backendClientReturnsOk, never())
+        .deleteFirebaseInstallation(TEST_API_KEY, TEST_FID_1, TEST_PROJECT_ID, TEST_REFRESH_TOKEN);
+  }
+
+  @Test
+  public void testDelete_serverError_failure() throws Exception {
+    // Update local storage with a registered fid entry
+    persistedFid.insertOrUpdatePersistedFidEntry(REGISTERED_FID_ENTRY);
+    FirebaseInstallations firebaseInstallations =
+        new FirebaseInstallations(
+            mockClock, executor, firebaseApp, backendClientReturnsError, persistedFid, mockUtils);
+
+    // Expect exception
+    try {
+      Tasks.await(firebaseInstallations.delete());
+      fail("delete() failed due to Server Error.");
+    } catch (ExecutionException expected) {
+      assertWithMessage("Exception class doesn't match")
+          .that(expected)
+          .hasCauseThat()
+          .isInstanceOf(FirebaseInstallationsException.class);
+      assertWithMessage("Exception status doesn't match")
+          .that(((FirebaseInstallationsException) expected.getCause()).getStatus())
+          .isEqualTo(FirebaseInstallationsException.Status.SDK_INTERNAL_ERROR);
+      PersistedFidEntry entryValue = persistedFid.readPersistedFidEntryValue();
+      assertWithMessage("Persisted Fid Entry doesn't match")
+          .that(entryValue)
+          .isEqualTo(REGISTERED_FID_ENTRY);
+    }
+  }
 }

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

@@ -156,7 +156,7 @@ public synchronized Task<InstallationTokenResult> getAuthToken(
   @NonNull
   @Override
   public Task<Void> delete() {
-    return Tasks.forResult(null);
+    return Tasks.call(executor, this::deleteFirebaseInstallationId);
   }
 
   /** Returns the application id of the {@link FirebaseApp} of this {@link FirebaseInstallations} */
@@ -400,6 +400,34 @@ private boolean isAuthTokenExpired(PersistedFidEntry persistedFidEntry) {
   private long currentTimeInSecs() {
     return TimeUnit.MILLISECONDS.toSeconds(clock.currentTimeMillis());
   }
+
+  /**
+   * Deletes the firebase installation id of the {@link FirebaseApp} from FIS servers and local
+   * storage.
+   */
+  private Void deleteFirebaseInstallationId() throws FirebaseInstallationsException {
+
+    PersistedFidEntry persistedFidEntry = persistedFid.readPersistedFidEntryValue();
+
+    if (isPersistedFidRegistered(persistedFidEntry)) {
+      // Call the FIS servers to delete this firebase installation id.
+      try {
+        serviceClient.deleteFirebaseInstallation(
+            firebaseApp.getOptions().getApiKey(),
+            persistedFidEntry.getFirebaseInstallationId(),
+            firebaseApp.getOptions().getProjectId(),
+            persistedFidEntry.getRefreshToken());
+
+      } catch (FirebaseInstallationServiceException exception) {
+        throw new FirebaseInstallationsException(
+            "Failed to delete a Firebase Installation.",
+            FirebaseInstallationsException.Status.SDK_INTERNAL_ERROR);
+      }
+    }
+
+    persistedFid.clear();
+    return null;
+  }
 }
 
 interface Supplier<T> {