/*
 * Copyright 2021 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
 *
 *   https://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.enterprise.connectedapps.internal;

import static com.google.common.truth.Truth.assertThat;
import static com.google.common.util.concurrent.MoreExecutors.directExecutor;

import android.os.Build.VERSION_CODES;
import com.google.android.enterprise.connectedapps.Profile;
import com.google.android.enterprise.connectedapps.internal.CrossProfileCallbackMultiMerger.CrossProfileCallbackMultiMergerCompleteListener;
import com.google.common.util.concurrent.FutureCallback;
import com.google.common.util.concurrent.Futures;
import com.google.common.util.concurrent.ListenableFuture;
import com.google.common.util.concurrent.SettableFuture;
import java.util.Map;
import java.util.concurrent.Executor;
import java.util.concurrent.Executors;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.robolectric.RobolectricTestRunner;
import org.robolectric.annotation.Config;

@RunWith(RobolectricTestRunner.class)
@Config(minSdk = VERSION_CODES.O)
public class CrossProfileCallbackMultiMergerTest {

  static class TestStringListener
      implements CrossProfileCallbackMultiMergerCompleteListener<String> {
    int timesResultsPosted = 0;
    Map<Profile, String> results;

    @Override
    public void onResult(Map<Profile, String> results) {
      timesResultsPosted++;
      this.results = results;
    }
  }

  private final Profile profile0 = Profile.fromInt(0);
  private final Profile profile1 = Profile.fromInt(1);
  private final Profile profile2 = Profile.fromInt(2);
  private static final String STRING = "String";

  private final TestStringListener stringListener = new TestStringListener();

  @Test
  public void onResult_expectedResultsNotReached_doesNotReportResult() {
    int expectedResults = 2;
    CrossProfileCallbackMultiMerger<String> merger =
        new CrossProfileCallbackMultiMerger<>(expectedResults, stringListener);

    merger.onResult(profile0, STRING);

    assertThat(stringListener.timesResultsPosted).isEqualTo(0);
  }

  @Test
  public void onResult_expectedResultsReached_doesReportResult() {
    int expectedResults = 2;
    CrossProfileCallbackMultiMerger<String> merger =
        new CrossProfileCallbackMultiMerger<>(expectedResults, stringListener);
    merger.onResult(profile0, STRING);

    merger.onResult(profile1, STRING);

    assertThat(stringListener.timesResultsPosted).isEqualTo(1);
  }

  @Test
  public void onResult_reportsCorrectResults() {
    int expectedResults = 2;
    CrossProfileCallbackMultiMerger<String> merger =
        new CrossProfileCallbackMultiMerger<>(expectedResults, stringListener);
    merger.onResult(profile0, STRING);

    merger.onResult(profile1, STRING);

    assertThat(stringListener.results.get(profile0)).isEqualTo(STRING);
    assertThat(stringListener.results.get(profile1)).isEqualTo(STRING);
  }

  @Test
  public void onResult_sameProfileReportsMultipleTimes_ignored() {
    int expectedResults = 2;
    CrossProfileCallbackMultiMerger<String> merger =
        new CrossProfileCallbackMultiMerger<>(expectedResults, stringListener);
    merger.onResult(profile0, STRING);

    merger.onResult(profile0, STRING);

    assertThat(stringListener.timesResultsPosted).isEqualTo(0);
  }

  @Test
  public void onResult_newResult_resultAlreadyReported_ignored() {
    int expectedResults = 2;
    CrossProfileCallbackMultiMerger<String> merger =
        new CrossProfileCallbackMultiMerger<>(expectedResults, stringListener);
    merger.onResult(profile0, STRING);
    merger.onResult(profile1, STRING);

    merger.onResult(profile2, STRING);

    assertThat(stringListener.timesResultsPosted).isEqualTo(1);
    assertThat(stringListener.results).doesNotContainKey(profile2);
  }

  @Test
  public void onResult_previousResultMissing_expectedResultsReached_doesReportResult() {
    int expectedResults = 2;
    CrossProfileCallbackMultiMerger<String> merger =
        new CrossProfileCallbackMultiMerger<>(expectedResults, stringListener);
    merger.missingResult(profile0);

    merger.onResult(profile1, STRING);

    assertThat(stringListener.timesResultsPosted).isEqualTo(1);
  }

  @Test
  public void missingResult_allResultsMissing_doesReportResult() {
    int expectedResults = 2;
    CrossProfileCallbackMultiMerger<String> merger =
        new CrossProfileCallbackMultiMerger<>(expectedResults, stringListener);
    merger.missingResult(profile0);

    merger.missingResult(profile1);

    assertThat(stringListener.timesResultsPosted).isEqualTo(1);
  }

  @Test
  public void missingResult_expectedResultsReached_doesReportResult() {
    int expectedResults = 2;
    CrossProfileCallbackMultiMerger<String> merger =
        new CrossProfileCallbackMultiMerger<>(expectedResults, stringListener);
    merger.onResult(profile1, STRING);

    merger.missingResult(profile0);

    assertThat(stringListener.timesResultsPosted).isEqualTo(1);
  }

  @Test
  public void missingResult_expectedResultsNotReached_doesNotReportResult() {
    int expectedResults = 2;
    CrossProfileCallbackMultiMerger<String> merger =
        new CrossProfileCallbackMultiMerger<>(expectedResults, stringListener);

    merger.missingResult(profile0);

    assertThat(stringListener.timesResultsPosted).isEqualTo(0);
  }

  @Test
  public void missingResult_resultAlreadyPosted_doesNotRecord() {
    int expectedResults = 2;
    CrossProfileCallbackMultiMerger<String> merger =
        new CrossProfileCallbackMultiMerger<>(expectedResults, stringListener);
    merger.onResult(profile0, STRING);

    merger.missingResult(profile0);
    merger.onResult(profile1, STRING);

    assertThat(stringListener.results.get(profile0)).isEqualTo(STRING);
  }

  @Test
  public void onResult_resultAlreadyPosted_doesNotRecord() {
    int expectedResults = 2;
    CrossProfileCallbackMultiMerger<String> merger =
        new CrossProfileCallbackMultiMerger<>(expectedResults, stringListener);
    merger.missingResult(profile0);

    merger.onResult(profile0, STRING);
    merger.onResult(profile1, STRING);

    assertThat(stringListener.results).doesNotContainKey(profile0);
  }

  @Test
  public void construct_noExpectedResults_reportsResultImmediately() {
    int expectedResults = 0;

    CrossProfileCallbackMultiMerger<String> unusedMerger =
        new CrossProfileCallbackMultiMerger<>(expectedResults, stringListener);

    assertThat(stringListener.timesResultsPosted).isEqualTo(1);
    assertThat(stringListener.results).isEmpty();
  }

  @Test
  // Do not ignore if this test turns flaky or times out, this likely highlights a real race
  // condition.
  public void listenableFuturesCompletingOnSeparateThreads() throws Exception {
    Executor executorWithThread1 = Executors.newSingleThreadExecutor();
    Executor executorWithThread2 = Executors.newSingleThreadExecutor();
    int aboutThatManyIterationsToBeRacy = 1000;

    for (int i = 0; i < aboutThatManyIterationsToBeRacy; i++) {
      ListenableFuture<String> future1 = Futures.submit(() -> "Hello", executorWithThread1);
      ListenableFuture<String> future2 = Futures.submit(() -> "World", executorWithThread2);
      int expectedResults = 2;
      SettableFuture<Map<Profile, String>> settableFuture = SettableFuture.create();
      CrossProfileCallbackMultiMerger<String> merger =
          new CrossProfileCallbackMultiMerger<>(expectedResults, settableFuture::set);
      Futures.addCallback(
          future1, new MergerFutureCallback<String>(profile0, merger), directExecutor());
      Futures.addCallback(
          future2, new MergerFutureCallback<String>(profile1, merger), directExecutor());

      Map<Profile, String> results = settableFuture.get();

      assertThat(results).containsExactly(profile0, "Hello", profile1, "World");
    }
  }

  @Test
  // Do not ignore if this test turns flaky or times out, this likely highlights a real race
  // condition.
  public void listenableFuturesCompletingWithErrorsOnSeparateThreads() throws Exception {
    Executor executorWithThread1 = Executors.newSingleThreadExecutor();
    Executor executorWithThread2 = Executors.newSingleThreadExecutor();
    int aboutThatManyIterationsToBeRacy = 1000;

    for (int i = 0; i < aboutThatManyIterationsToBeRacy; i++) {
      ListenableFuture<String> future1 = Futures.submit(() -> "Hello", executorWithThread1);
      ListenableFuture<String> future2 =
          Futures.submit(
              () -> {
                throw new RuntimeException("Whoopsies");
              },
              executorWithThread2);
      int expectedResults = 2;
      SettableFuture<Map<Profile, String>> settableFuture = SettableFuture.create();
      CrossProfileCallbackMultiMerger<String> merger =
          new CrossProfileCallbackMultiMerger<>(expectedResults, settableFuture::set);
      Futures.addCallback(
          future1, new MergerFutureCallback<String>(profile0, merger), directExecutor());
      Futures.addCallback(
          future2, new MergerFutureCallback<String>(profile1, merger), directExecutor());

      Map<Profile, String> results = settableFuture.get();

      assertThat(results).containsExactly(profile0, "Hello");
    }
  }

  private static class MergerFutureCallback<E> implements FutureCallback<E> {

    private final Profile profileId;
    private final CrossProfileCallbackMultiMerger<E> merger;

    MergerFutureCallback(Profile profileId, CrossProfileCallbackMultiMerger<E> merger) {
      this.profileId = profileId;
      this.merger = merger;
    }

    @Override
    public void onSuccess(E result) {
      merger.onResult(profileId, result);
    }

    @Override
    public void onFailure(Throwable t) {
      merger.missingResult(profileId);
    }
  }
}