Put DownloadTasks on hold until preceding conflicting tasks are complete

Tasks conflict if both of them work on the same media and at least one
of them is remove action.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=172741795

library/core/src/androidTest/java/com/google/android/exoplayer2/offline/DownloadManagerTest.java

+/*
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * 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.android.exoplayer2.offline;
+
+import android.os.ConditionVariable;
+import android.support.annotation.Nullable;
+import android.test.InstrumentationTestCase;
+import com.google.android.exoplayer2.offline.DownloadManager.DownloadListener;
+import com.google.android.exoplayer2.offline.DownloadManager.DownloadTask;
+import com.google.android.exoplayer2.offline.DownloadManager.DownloadTask.State;
+import com.google.android.exoplayer2.upstream.DummyDataSource;
+import com.google.android.exoplayer2.upstream.cache.Cache;
+import com.google.android.exoplayer2.util.ClosedSource;
+import java.io.DataOutputStream;
+import java.io.IOException;
+import java.util.concurrent.Executors;
+import org.mockito.Mockito;
+import org.mockito.MockitoAnnotations;
+
+/** Tests {@link DownloadManager}. */
+@ClosedSource(reason = "Not ready yet")
+public class DownloadManagerTest extends InstrumentationTestCase {
+
+  /* Used to check if condition becomes true in this time interval. */
+  private static final int ASSERT_TRUE_TIMEOUT = 1000;
+  /* Used to check if condition stays false for this time interval. */
+  private static final int ASSERT_FALSE_TIME = 1000;
+
+  private DownloadManager downloadManager;
+  private ConditionVariable downloadFinishedCondition;
+  private Throwable downloadError;
+
+  @Override
+  public void setUp() throws Exception {
+    super.setUp();
+    setUpMockito(this);
+
+    downloadManager = new DownloadManager(
+        new DownloaderConstructorHelper(Mockito.mock(Cache.class), DummyDataSource.FACTORY),
+        Executors.newCachedThreadPool());
+
+    downloadFinishedCondition = new ConditionVariable();
+    downloadManager.setListener(new TestDownloadListener());
+  }
+
+  class TestDownloadListener implements DownloadListener {
+    @Override
+    public void onStateChange(DownloadManager downloadManager, DownloadTask downloadTask, int state,
+        Throwable error) {
+      if (state == DownloadTask.STATE_ERROR && downloadError == null) {
+        downloadError = error;
+      }
+      ((FakeDownloadAction) downloadTask.getDownloadAction()).onStateChange();
+    }
+
+    @Override
+    public void onTasksFinished(DownloadManager downloadManager) {
+      downloadFinishedCondition.open();
+    }
+  }
+
+  public void testDownloadActionRuns() throws Throwable {
+    doTestActionRuns(createDownloadAction("media 1"));
+  }
+
+  public void testRemoveActionRuns() throws Throwable {
+    doTestActionRuns(createRemoveAction("media 1"));
+  }
+
+  public void testDifferentMediaDownloadActionsStartInParallel() throws Throwable {
+    doTestActionsRunInParallel(createDownloadAction("media 1"),
+        createDownloadAction("media 2"));
+  }
+
+  public void testDifferentMediaDifferentActionsStartInParallel() throws Throwable {
+    doTestActionsRunInParallel(createDownloadAction("media 1"),
+        createRemoveAction("media 2"));
+  }
+
+  public void testSameMediaDownloadActionsStartInParallel() throws Throwable {
+    doTestActionsRunInParallel(createDownloadAction("media 1"),
+        createDownloadAction("media 1"));
+  }
+
+  public void testSameMediaRemoveActionWaitsDownloadAction() throws Throwable {
+    doTestActionsRunSequentially(createDownloadAction("media 1"),
+        createRemoveAction("media 1"));
+  }
+
+  public void testSameMediaDownloadActionWaitsRemoveAction() throws Throwable {
+    doTestActionsRunSequentially(createRemoveAction("media 1"),
+        createDownloadAction("media 1"));
+  }
+
+  public void testSameMediaRemoveActionWaitsRemoveAction() throws Throwable {
+    doTestActionsRunSequentially(createRemoveAction("media 1"),
+        createRemoveAction("media 1"));
+  }
+
+  public void testSameMediaMultipleActions() throws Throwable {
+    FakeDownloadAction downloadAction1 = createDownloadAction("media 1").ignoreInterrupts();
+    FakeDownloadAction downloadAction2 = createDownloadAction("media 1").ignoreInterrupts();
+    FakeDownloadAction removeAction1 = createRemoveAction("media 1");
+    FakeDownloadAction downloadAction3 = createDownloadAction("media 1");
+    FakeDownloadAction removeAction2 = createRemoveAction("media 1");
+
+    // Two download actions run in parallel.
+    downloadAction1.post().assertStarted();
+    downloadAction2.post().assertStarted();
+    // removeAction1 is added. It interrupts the two download actions' threads but they are
+    // configured to ignore it so removeAction1 doesn't start.
+    removeAction1.post().assertDoesNotStart();
+
+    // downloadAction2 finishes but it isn't enough to start removeAction1.
+    downloadAction2.finishAndAssertFinished();
+    removeAction1.assertDoesNotStart();
+    // downloadAction3 is post to DownloadManager but it waits for removeAction1 to finish.
+    downloadAction3.post().assertDoesNotStart();
+
+    // When downloadAction1 finishes, removeAction1 starts.
+    downloadAction1.finishAndAssertFinished();
+    removeAction1.assertStarted();
+    // downloadAction3 still waits removeAction1
+    downloadAction3.assertDoesNotStart();
+
+    // removeAction2 is posted. removeAction1 and downloadAction3 is canceled so removeAction2
+    // starts immediately.
+    removeAction2.post().assertStarted().finishAndAssertFinished();
+    blockUntilTasksCompleteAndThrowAnyDownloadError();
+  }
+
+  public void testMultipleWaitingAction() throws Throwable {
+    FakeDownloadAction removeAction1 = createRemoveAction("media 1").ignoreInterrupts();
+    FakeDownloadAction removeAction2 = createRemoveAction("media 1");
+    FakeDownloadAction removeAction3 = createRemoveAction("media 1");
+
+    removeAction1.post().assertStarted();
+    removeAction2.post().assertDoesNotStart();
+    removeAction3.post().assertDoesNotStart();
+
+    removeAction1.finishAndAssertFinished();
+    removeAction2.assertTaskState(DownloadTask.STATE_CANCELLED);
+    removeAction3.assertStarted().finishAndAssertFinished();
+
+    blockUntilTasksCompleteAndThrowAnyDownloadError();
+  }
+
+  private void doTestActionRuns(FakeDownloadAction action) throws Throwable {
+    action.post().assertStarted().finishAndAssertFinished();
+    blockUntilTasksCompleteAndThrowAnyDownloadError();
+  }
+
+  private void doTestActionsRunSequentially(FakeDownloadAction action1,
+      FakeDownloadAction action2) throws Throwable {
+    action1.ignoreInterrupts().post().assertStarted();
+    action2.post().assertDoesNotStart();
+
+    action1.finishAndAssertFinished();
+    action2.assertStarted();
+
+    action2.finishAndAssertFinished();
+    blockUntilTasksCompleteAndThrowAnyDownloadError();
+  }
+
+  private void doTestActionsRunInParallel(FakeDownloadAction action1,
+      FakeDownloadAction action2) throws Throwable {
+    action1.post().assertStarted();
+    action2.post().assertStarted();
+    action1.finishAndAssertFinished();
+    action2.finishAndAssertFinished();
+    blockUntilTasksCompleteAndThrowAnyDownloadError();
+  }
+
+  private FakeDownloadAction createDownloadAction(String mediaId) {
+    return new FakeDownloadAction(downloadManager, mediaId, false);
+  }
+
+  private FakeDownloadAction createRemoveAction(String mediaId) {
+    return new FakeDownloadAction(downloadManager, mediaId, true);
+  }
+
+  private void blockUntilTasksCompleteAndThrowAnyDownloadError() throws Throwable {
+    assertTrue(downloadFinishedCondition.block(ASSERT_TRUE_TIMEOUT));
+    downloadFinishedCondition.close();
+    if (downloadError != null) {
+      throw downloadError;
+    }
+  }
+
+  /**
+   * Sets up Mockito for an instrumentation test.
+   */
+  private static void setUpMockito(InstrumentationTestCase instrumentationTestCase) {
+    // Workaround for https://code.google.com/p/dexmaker/issues/detail?id=2.
+    System.setProperty("dexmaker.dexcache",
+        instrumentationTestCase.getInstrumentation().getTargetContext().getCacheDir().getPath());
+    MockitoAnnotations.initMocks(instrumentationTestCase);
+  }
+
+  private static class FakeDownloadAction extends DownloadAction {
+
+    private final DownloadManager downloadManager;
+    private final String mediaId;
+    private final boolean removeAction;
+    private final FakeDownloader downloader;
+    private final ConditionVariable stateChanged;
+    private DownloadTask downloadTask;
+
+    private FakeDownloadAction(DownloadManager downloadManager, String mediaId,
+        boolean removeAction) {
+      this.downloadManager = downloadManager;
+      this.mediaId = mediaId;
+      this.removeAction = removeAction;
+      this.downloader = new FakeDownloader(removeAction);
+      this.stateChanged = new ConditionVariable();
+    }
+
+    @Override
+    protected String getType() {
+      return "FakeDownloadAction";
+    }
+
+    @Override
+    protected void writeToStream(DataOutputStream output) throws IOException {
+      throw new UnsupportedOperationException();
+    }
+
+    @Override
+    protected boolean isRemoveAction() {
+      return removeAction;
+    }
+
+    @Override
+    protected boolean isSameMedia(DownloadAction other) {
+      return other instanceof FakeDownloadAction
+          && mediaId.equals(((FakeDownloadAction) other).mediaId);
+    }
+
+    @Override
+    protected Downloader createDownloader(DownloaderConstructorHelper downloaderConstructorHelper) {
+      return downloader;
+    }
+
+    private FakeDownloadAction post() throws DownloadException {
+      downloadTask = downloadManager.handleAction(this);
+      return this;
+    }
+
+    private FakeDownloadAction assertDoesNotStart() {
+      assertFalse(downloader.started.block(ASSERT_FALSE_TIME));
+      return this;
+    }
+
+    private FakeDownloadAction assertStarted() {
+      assertTrue(downloader.started.block(ASSERT_TRUE_TIMEOUT));
+      assertTaskState(DownloadTask.STATE_STARTED);
+      return this;
+    }
+
+    private FakeDownloadAction assertTaskState(@State int state) {
+      assertTrue(stateChanged.block(ASSERT_TRUE_TIMEOUT));
+      stateChanged.close();
+      assertEquals(state, downloadTask.getState());
+      return this;
+    }
+
+    private FakeDownloadAction finishAndAssertFinished() {
+      downloader.finish.open();
+      assertTaskState(DownloadTask.STATE_ENDED);
+      return this;
+    }
+
+    private FakeDownloadAction ignoreInterrupts() {
+      downloader.ignoreInterrupts = true;
+      return this;
+    }
+
+    private void onStateChange() {
+      stateChanged.open();
+    }
+  }
+
+  private static class FakeDownloader implements Downloader {
+    private final ConditionVariable started;
+    private final com.google.android.exoplayer2.util.ConditionVariable finish;
+    private final boolean removeAction;
+    private boolean ignoreInterrupts;
+
+    private FakeDownloader(boolean removeAction) {
+      this.removeAction = removeAction;
+      this.started = new ConditionVariable();
+      this.finish = new com.google.android.exoplayer2.util.ConditionVariable();
+    }
+
+    @Override
+    public void init() throws InterruptedException, IOException {
+      // do nothing.
+    }
+
+    @Override
+    public void download(@Nullable ProgressListener listener)
+        throws InterruptedException, IOException {
+      assertFalse(removeAction);
+      started.open();
+      blockUntilFinish();
+    }
+
+    @Override
+    public void remove() throws InterruptedException {
+      assertTrue(removeAction);
+      started.open();
+      blockUntilFinish();
+    }
+
+    private void blockUntilFinish() throws InterruptedException {
+      while (true){
+        try {
+          finish.block();
+          break;
+        } catch (InterruptedException e) {
+          if (!ignoreInterrupts) {
+            throw e;
+          }
+        }
+      }
+    }
+
+    @Override
+    public long getDownloadedBytes() {
+      return 0;
+    }
+
+    @Override
+    public float getDownloadPercentage() {
+      return 0;
+    }
+  }
+
+}

library/core/src/main/java/com/google/android/exoplayer2/offline/DownloadException.java

@@ -25,4 +25,9 @@ public final class DownloadException extends IOException {
     super(message);
   }
 
+  /** @param cause The cause for the exception. */
+  public DownloadException(Throwable cause) {
+    super(cause);
+  }
+
 }

library/core/src/main/java/com/google/android/exoplayer2/util/ConditionVariable.java

@@ -16,8 +16,8 @@
 package com.google.android.exoplayer2.util;
 
 /**
- * A condition variable whose {@link #open()} and {@link #close()} methods return whether they
- * resulted in a change of state.
+ * An interruptible condition variable whose {@link #open()} and {@link #close()} methods return
+ * whether they resulted in a change of state.
  */
 public final class ConditionVariable {
 
@@ -59,4 +59,21 @@ public final class ConditionVariable {
     }
   }
 
+  /**
+   * Blocks until the condition is opened or until timeout milliseconds have passed.
+   *
+   * @param timeout The maximum time to wait in milliseconds.
+   * @return true If the condition was opened, false if the call returns because of the timeout.
+   * @throws InterruptedException If the thread is interrupted.
+   */
+  public synchronized boolean block(int timeout) throws InterruptedException {
+    long now = System.currentTimeMillis();
+    long end = now + timeout;
+    while (!isOpen && now < end) {
+      wait(end - now);
+      now = System.currentTimeMillis();
+    }
+    return isOpen;
+  }
+
 }