Update to background thread execution for listDownloadModels call.

Author: annzimmer

firebase-ml-modeldownloader/src/main/java/com/google/firebase/ml/modeldownloader/FirebaseModelDownloader.java

@@ -18,28 +18,36 @@
 import androidx.annotation.VisibleForTesting;
 import com.google.android.gms.common.internal.Preconditions;
 import com.google.android.gms.tasks.Task;
-import com.google.android.gms.tasks.Tasks;
+import com.google.android.gms.tasks.TaskCompletionSource;
 import com.google.firebase.FirebaseApp;
 import com.google.firebase.FirebaseOptions;
 import com.google.firebase.ml.modeldownloader.internal.SharedPreferencesUtil;
 import java.util.Set;
+import java.util.concurrent.Executor;
+import java.util.concurrent.Executors;
 
 public class FirebaseModelDownloader {
 
   private final FirebaseOptions firebaseOptions;
   private final SharedPreferencesUtil sharedPreferencesUtil;
+  private final Executor executor;
 
   FirebaseModelDownloader(FirebaseApp firebaseApp) {
     this.firebaseOptions = firebaseApp.getOptions();
     this.sharedPreferencesUtil = new SharedPreferencesUtil(firebaseApp);
+    this.executor = Executors.newCachedThreadPool();
   }
 
   @VisibleForTesting
   FirebaseModelDownloader(
-      FirebaseOptions firebaseOptions, SharedPreferencesUtil sharedPreferencesUtil) {
+      FirebaseOptions firebaseOptions,
+      SharedPreferencesUtil sharedPreferencesUtil,
+      Executor executor) {
     this.firebaseOptions = firebaseOptions;
     this.sharedPreferencesUtil = sharedPreferencesUtil;
+    this.executor = executor;
   }
+
   /**
    * Returns the {@link FirebaseModelDownloader} initialized with the default {@link FirebaseApp}.
    *
@@ -94,7 +102,10 @@ public Task<CustomModel> getModel(
   /** @return The set of all models that are downloaded to this device. */
   @NonNull
   public Task<Set<CustomModel>> listDownloadedModels() {
-    return Tasks.forResult(sharedPreferencesUtil.listDownloadedModels());
+    TaskCompletionSource<Set<CustomModel>> taskCompletionSource = new TaskCompletionSource<>();
+    executor.execute(
+        () -> taskCompletionSource.setResult(sharedPreferencesUtil.listDownloadedModels()));
+    return taskCompletionSource.getTask();
   }
 
   /*

firebase-ml-modeldownloader/src/main/java/com/google/firebase/ml/modeldownloader/internal/SharedPreferencesUtil.java

@@ -209,11 +209,28 @@ public synchronized Set<CustomModel> listDownloadedModels() {
         if (extractModel != null) {
           customModels.add(extractModel);
         }
+      } else {
+        matcher = Pattern.compile(DOWNLOADING_MODEL_ID_PATTERN).matcher(key);
+        if (matcher.find()) {
+          String modelName = matcher.group(matcher.groupCount());
+          CustomModel extractModel = isDownloadCompleted(modelName);
+          if (extractModel != null) {
+            customModels.add(extractModel);
+          }
+        }
       }
     }
     return customModels;
   }
 
+  synchronized CustomModel isDownloadCompleted(String modelName) {
+    CustomModel downloadModel = getCustomModelDetails(modelName);
+    // TODO(annz) check here if download currently in progress have completed.
+    // if yes, then complete file relocation and return the updated model, otherwise return null
+
+    return null;
+  }
+
   /**
    * Clears all stored data related to a custom model download.
    *

firebase-ml-modeldownloader/src/test/java/com/google/firebase/ml/modeldownloader/FirebaseModelDownloaderTest.java

@@ -17,7 +17,6 @@
 import static com.google.common.truth.Truth.assertThat;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertThrows;
-import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.when;
 
 import androidx.test.core.app.ApplicationProvider;
@@ -28,9 +27,17 @@
 import com.google.firebase.ml.modeldownloader.internal.SharedPreferencesUtil;
 import java.util.Collections;
 import java.util.Set;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.LinkedBlockingQueue;
+import java.util.concurrent.ThreadPoolExecutor;
+import java.util.concurrent.TimeUnit;
+import org.junit.After;
 import org.junit.Before;
 import org.junit.Test;
 import org.junit.runner.RunWith;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
 import org.robolectric.RobolectricTestRunner;
 
 @RunWith(RobolectricTestRunner.class)
@@ -51,14 +58,28 @@ public class FirebaseModelDownloaderTest {
   CustomModel CUSTOM_MODEL = new CustomModel(MODEL_NAME, 0, 100, MODEL_HASH);
 
   FirebaseModelDownloader firebaseModelDownloader;
-  SharedPreferencesUtil mockPrefs = mock(SharedPreferencesUtil.class);
+  @Mock SharedPreferencesUtil mockPrefs;
+
+  ExecutorService executor;
 
   @Before
   public void setUp() {
+    MockitoAnnotations.initMocks(this);
     FirebaseApp.clearInstancesForTest();
     // default app
     FirebaseApp.initializeApp(ApplicationProvider.getApplicationContext(), FIREBASE_OPTIONS);
-    firebaseModelDownloader = new FirebaseModelDownloader(FIREBASE_OPTIONS, mockPrefs);
+
+    executor = new ThreadPoolExecutor(0, 1, 30L, TimeUnit.SECONDS, new LinkedBlockingQueue<>());
+    firebaseModelDownloader = new FirebaseModelDownloader(FIREBASE_OPTIONS, mockPrefs, executor);
+  }
+
+  @After
+  public void cleanUp() {
+    try {
+      executor.awaitTermination(250, TimeUnit.MILLISECONDS);
+    } catch (InterruptedException e) {
+      // do nothing.
+    }
   }
 
   @Test
@@ -71,19 +92,32 @@ public void getModel_unimplemented() {
   }
 
   @Test
-  public void listDownloadedModels_returnsEmptyModelList() {
+  public void listDownloadedModels_returnsEmptyModelList()
+      throws ExecutionException, InterruptedException {
     when(mockPrefs.listDownloadedModels()).thenReturn(Collections.emptySet());
+    TestOnCompleteListener<Set<CustomModel>> onCompleteListener = new TestOnCompleteListener<>();
     Task<Set<CustomModel>> task = firebaseModelDownloader.listDownloadedModels();
+    task.addOnCompleteListener(executor, onCompleteListener);
+    Set<CustomModel> customModelSet = onCompleteListener.await();
+
     assertThat(task.isComplete()).isTrue();
-    assertEquals(task.getResult(), Collections.EMPTY_SET);
+    assertEquals(customModelSet, Collections.EMPTY_SET);
   }
 
   @Test
-  public void listDownloadedModels_returnsModelList() {
+  public void listDownloadedModels_returnsModelList()
+      throws ExecutionException, InterruptedException {
     when(mockPrefs.listDownloadedModels()).thenReturn(Collections.singleton(CUSTOM_MODEL));
+
+    TestOnCompleteListener<Set<CustomModel>> onCompleteListener = new TestOnCompleteListener<>();
     Task<Set<CustomModel>> task = firebaseModelDownloader.listDownloadedModels();
+    task.addOnCompleteListener(executor, onCompleteListener);
+    Set<CustomModel> customModelSet = onCompleteListener.await();
+
     assertThat(task.isComplete()).isTrue();
-    assertEquals(task.getResult(), Collections.singleton(CUSTOM_MODEL));
+    assertEquals(customModelSet, Collections.singleton(CUSTOM_MODEL));
+
+    executor.awaitTermination(500, TimeUnit.MILLISECONDS);
   }
 
   @Test

firebase-ml-modeldownloader/src/test/java/com/google/firebase/ml/modeldownloader/TestOnCompleteListener.java

@@ -0,0 +1,68 @@
+// 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.ml.modeldownloader;
+
+import androidx.annotation.NonNull;
+import com.google.android.gms.tasks.OnCompleteListener;
+import com.google.android.gms.tasks.Task;
+import java.io.IOException;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.TimeUnit;
+
+/**
+ * Helper listener that works around a limitation of the Tasks API where await() cannot be called on
+ * the main thread. This listener works around it by running itself on a different thread, thus
+ * allowing the main thread to be woken up when the Tasks complete.
+ */
+public class TestOnCompleteListener<TResult> implements OnCompleteListener<TResult> {
+  private static final long TIMEOUT_MS = 5000;
+  private final CountDownLatch latch = new CountDownLatch(1);
+  private Task<TResult> task;
+  private volatile TResult result;
+  private volatile Exception exception;
+  private volatile boolean successful;
+
+  @Override
+  public void onComplete(@NonNull Task<TResult> task) {
+    this.task = task;
+    successful = task.isSuccessful();
+    if (successful) {
+      result = task.getResult();
+    } else {
+      exception = task.getException();
+    }
+    latch.countDown();
+  }
+
+  /** Blocks until the {@link #onComplete} is called. */
+  public TResult await() throws InterruptedException, ExecutionException {
+    if (!latch.await(TIMEOUT_MS, TimeUnit.MILLISECONDS)) {
+      throw new InterruptedException("timed out waiting for result");
+    }
+    if (successful) {
+      return result;
+    } else {
+      if (exception instanceof InterruptedException) {
+        throw (InterruptedException) exception;
+      }
+      // todo(annz) add firebase ml exception handling here.
+      if (exception instanceof IOException) {
+        throw new ExecutionException(exception);
+      }
+      throw new IllegalStateException("got an unexpected exception type", exception);
+    }
+  }
+}