/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.beam.runners.dataflow.worker.util.common.worker;

import static org.apache.beam.runners.dataflow.worker.ReaderTestUtils.positionAtIndex;
import static org.apache.beam.runners.dataflow.worker.ReaderTestUtils.splitRequestAtIndex;
import static org.apache.beam.runners.dataflow.worker.SourceTranslationUtils.cloudPositionToReaderPosition;
import static org.apache.beam.runners.dataflow.worker.SourceTranslationUtils.cloudProgressToReaderProgress;
import static org.apache.beam.runners.dataflow.worker.SourceTranslationUtils.readerProgressToCloudProgress;
import static org.apache.beam.runners.dataflow.worker.SourceTranslationUtils.splitRequestToApproximateSplitRequest;
import static org.apache.beam.runners.dataflow.worker.SourceTranslationUtils.toCloudPosition;
import static org.apache.beam.runners.dataflow.worker.counters.CounterName.named;
import static org.apache.beam.runners.dataflow.worker.util.common.worker.TestOutputReceiver.TestOutputCounter.getMeanByteCounterName;
import static org.apache.beam.runners.dataflow.worker.util.common.worker.TestOutputReceiver.TestOutputCounter.getObjectCounterName;
import static org.hamcrest.MatcherAssert.assertThat;
import static org.hamcrest.Matchers.containsInAnyOrder;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertNotNull;
import static org.junit.Assert.assertNull;
import static org.junit.Assert.assertTrue;
import static org.mockito.Matchers.any;
import static org.mockito.Matchers.anyBoolean;
import static org.mockito.Matchers.anyLong;
import static org.mockito.Matchers.eq;
import static org.mockito.Mockito.mock;
import static org.mockito.Mockito.verify;
import static org.mockito.Mockito.verifyNoMoreInteractions;
import static org.mockito.Mockito.when;

import com.google.api.services.dataflow.model.ApproximateReportedProgress;
import com.google.api.services.dataflow.model.ApproximateSplitRequest;
import com.google.api.services.dataflow.model.Position;
import java.io.IOException;
import java.util.Arrays;
import java.util.NoSuchElementException;
import java.util.concurrent.BrokenBarrierException;
import java.util.concurrent.CyclicBarrier;
import java.util.concurrent.Exchanger;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.TimeUnit;
import org.apache.beam.runners.dataflow.worker.InMemoryReader;
import org.apache.beam.runners.dataflow.worker.NameContextsForTests;
import org.apache.beam.runners.dataflow.worker.TestOperationContext;
import org.apache.beam.runners.dataflow.worker.counters.Counter.CounterUpdateExtractor;
import org.apache.beam.runners.dataflow.worker.counters.CounterFactory.LongCounterMean;
import org.apache.beam.runners.dataflow.worker.counters.CounterSet;
import org.apache.beam.runners.dataflow.worker.counters.NameContext;
import org.apache.beam.runners.dataflow.worker.util.common.worker.ExecutorTestUtils.TestReader;
import org.apache.beam.sdk.coders.StringUtf8Coder;
import org.apache.beam.sdk.io.range.OffsetRangeTracker;
import org.apache.beam.vendor.guava.v26_0_jre.com.google.common.base.Preconditions;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.junit.runners.JUnit4;

/** Tests for ReadOperation. */
@RunWith(JUnit4.class)
@SuppressWarnings({
  "nullness" // TODO(https://issues.apache.org/jira/browse/BEAM-10402)
})
public class ReadOperationTest {

  private static final String COUNTER_PREFIX = "test-";
  private final CounterSet counterSet = new CounterSet();
  private OperationContext context =
      TestOperationContext.create(
          counterSet,
          NameContext.create("test", "ReadOperation", "ReadOperation", "ReadOperation"));

  /**
   * Tests that a {@link ReadOperation} has expected counters, and that their values are reasonable.
   */
  @Test
  @SuppressWarnings("unchecked")
  public void testRunReadOperation() throws Exception {
    TestReader reader = new TestReader("hi", "there", "", "bob");

    TestOutputReceiver receiver =
        new TestOutputReceiver(
            counterSet,
            NameContext.create("test", "test_receiver", "test_receiver", "test_receiver"));
    ReadOperation readOperation = ReadOperation.forTest(reader, receiver, context);

    readOperation.start();
    readOperation.finish();

    assertThat(receiver.outputElems, containsInAnyOrder((Object) "hi", "there", "", "bob"));

    CounterUpdateExtractor<?> updateExtractor = mock(CounterUpdateExtractor.class);
    counterSet.extractUpdates(false, updateExtractor);
    verify(updateExtractor)
        .longSum(eq(getObjectCounterName("test_receiver_out")), anyBoolean(), eq(4L));
    verify(updateExtractor)
        .longMean(
            eq(getMeanByteCounterName("test_receiver_out")),
            anyBoolean(),
            eq(LongCounterMean.ZERO.addValue(14L, 4)));
    verify(updateExtractor).longSum(eq(named("ReadOperation-ByteCount")), anyBoolean(), eq(10L));
    verifyNoMoreInteractions(updateExtractor);
  }

  private static class ManualScheduler {
    private CyclicBarrier beforeRun = new CyclicBarrier(2 /* test thread and loop thread */);
    private CyclicBarrier afterRun = new CyclicBarrier(2 /* test thread and loop thread */);

    private final ScheduledExecutorService realExecutor =
        Executors.newSingleThreadScheduledExecutor();
    private final ScheduledExecutorService executor;

    public ManualScheduler() {
      executor = mock(ScheduledExecutorService.class);
      when(executor.scheduleAtFixedRate(
              any(Runnable.class), anyLong(), anyLong(), any(TimeUnit.class)))
          .then(invocation -> schedule(invocation.getArgument(0, Runnable.class)));
    }

    public ScheduledExecutorService getExecutor() {
      return executor;
    }

    private ScheduledFuture<?> schedule(final Runnable runnable) {
      return realExecutor.schedule(
          new Runnable() {
            @Override
            public void run() {
              while (true) {
                try {
                  beforeRun.await();
                  runnable.run();
                  afterRun.await();
                } catch (InterruptedException | BrokenBarrierException e) {
                  break;
                }
              }
            }
          },
          0,
          TimeUnit.MILLISECONDS);
    }

    public void runOnce() throws Exception {
      beforeRun.await();
      afterRun.await();
    }
  }

  @Test
  public void testGetProgress() throws Exception {
    MockReaderIterator iterator = new MockReaderIterator(0, 5);
    MockOutputReceiver receiver = new MockOutputReceiver();

    ManualScheduler scheduler = new ManualScheduler();
    final ReadOperation readOperation =
        ReadOperation.forTest(new MockReader(iterator), receiver, scheduler.getExecutor(), context);

    Thread thread = runReadLoopInThread(readOperation);
    for (int i = 0; i < 5; ++i) {
      // Reader currently blocked in start()/advance().
      // Ensure that getProgress() doesn't block while the reader advances.
      ApproximateReportedProgress progress =
          readerProgressToCloudProgress(readOperation.getProgress());
      Long observedIndex =
          (progress == null) ? null : progress.getPosition().getRecordIndex().longValue();
      assertTrue(
          "Actual: " + observedIndex + " instead of " + i,
          (i == 0 && progress == null) || i == observedIndex || i == observedIndex + 1);
      iterator.offerNext(i);
      // Now the reader is not blocked (instead the receiver is blocked): progress can be
      // updated. Wait for it to be updated.
      scheduler.runOnce();

      receiver.unblockProcess();
    }
    thread.join();
  }

  @Test
  public void testGetProgressIsNotStaleForSlowProcessedElements() throws Exception {
    MockReaderIterator iterator = new MockReaderIterator(0, 5);
    MockOutputReceiver receiver = new MockOutputReceiver();

    ManualScheduler scheduler = new ManualScheduler();
    final ReadOperation readOperation =
        ReadOperation.forTest(new MockReader(iterator), receiver, scheduler.getExecutor(), context);

    Thread thread = runReadLoopInThread(readOperation);
    iterator.offerNext(0); // The reader will read 0, report progress 0 and be stuck processing it.
    // Wait for the progress thread to be triggered once.
    scheduler.runOnce();
    // Check that progress position is 0.
    ApproximateReportedProgress progress =
        readerProgressToCloudProgress(readOperation.getProgress());
    assertEquals(0, progress.getPosition().getRecordIndex().longValue());
    // Quickly go through 1, 2, 3.
    receiver.unblockProcess();
    iterator.offerNext(1);
    receiver.unblockProcess();
    iterator.offerNext(2);
    receiver.unblockProcess();
    iterator.offerNext(3);
    // We are now blocked in processing 3.
    // Wait for the progress thread to be triggered at least once.
    scheduler.runOnce();
    // Check that the progress position is not stale.
    progress = readerProgressToCloudProgress(readOperation.getProgress());
    assertEquals(3, progress.getPosition().getRecordIndex().longValue());
    // Complete the read.
    receiver.unblockProcess();
    iterator.offerNext(4);
    receiver.unblockProcess();
    thread.join();
  }

  @Test
  public void testCheckpoint() throws Exception {
    InMemoryReader<String> reader =
        new InMemoryReader<>(
            Arrays.asList("0", "1", "2", "3", "4", "5", "6", "7", "8", "9"),
            0,
            10,
            StringUtf8Coder.of());
    final ReadOperation[] readOperationHolder = new ReadOperation[1];
    OutputReceiver receiver =
        new OutputReceiver() {
          @Override
          public void process(Object elem) throws Exception {
            ReadOperation readOperation = readOperationHolder[0];
            if ("1".equals(elem)) {
              NativeReader.DynamicSplitResultWithPosition split =
                  (NativeReader.DynamicSplitResultWithPosition) readOperation.requestCheckpoint();
              assertNotNull(split);
              assertEquals(positionAtIndex(2L), toCloudPosition(split.getAcceptedPosition()));

              // Check that the progress has been recomputed.
              ApproximateReportedProgress progress =
                  readerProgressToCloudProgress(readOperation.getProgress());
              assertEquals(1, progress.getPosition().getRecordIndex().longValue());
            }
          }
        };
    ReadOperation readOperation = ReadOperation.forTest(reader, receiver, context);
    readOperation.setProgressUpdatePeriodMs(ReadOperation.UPDATE_ON_EACH_ITERATION);
    readOperationHolder[0] = readOperation;

    // An unstarted ReadOperation refuses checkpoint requests.
    assertNull(readOperation.requestCheckpoint());

    readOperation.start();
    readOperation.finish();

    // Operation is now finished. Check that it refuses a checkpoint request.
    assertNull(readOperation.requestCheckpoint());
  }

  @Test
  public void testCheckpointDoesNotBlock() throws Exception {
    MockReaderIterator iterator = new MockReaderIterator(0, 10);
    MockOutputReceiver receiver = new MockOutputReceiver();
    ReadOperation readOperation =
        ReadOperation.forTest(new MockReader(iterator), receiver, context);

    // We get the read loop started and then wait for it to block.  At that point, the iterator
    // should have a current of 1.  We then checkpoint without offering a new value.  That should
    // succeed with checkpoint position of 2.  By then offerring 1, then run loop should exit.
    Thread thread = runReadLoopInThread(readOperation);
    iterator.offerNext(0);
    iterator.blockInNextAdvance();
    receiver.unblockProcess();
    iterator.awaitBlockedInAdvance();

    NativeReader.DynamicSplitResultWithPosition split =
        (NativeReader.DynamicSplitResultWithPosition) readOperation.requestCheckpoint();
    assertNotNull(split);
    assertEquals(positionAtIndex(2L), toCloudPosition(split.getAcceptedPosition()));

    iterator.offerNext(1);
    receiver.unblockProcess();

    thread.join();
  }

  @Test
  public void testDynamicSplit() throws Exception {
    InMemoryReader<String> reader =
        new InMemoryReader<>(
            Arrays.asList("0", "1", "2", "3", "4", "5", "6", "7", "8", "9"),
            0,
            10,
            StringUtf8Coder.of());
    final ReadOperation[] operationHolder = new ReadOperation[1];
    OutputReceiver receiver =
        new OutputReceiver() {
          @Override
          public void process(Object elem) throws Exception {
            ReadOperation readOperation = operationHolder[0];
            if ("1".equals(elem)) {
              NativeReader.DynamicSplitResultWithPosition split =
                  (NativeReader.DynamicSplitResultWithPosition)
                      readOperation.requestDynamicSplit(splitRequestAtIndex(8L));
              assertNotNull(split);
              assertEquals(positionAtIndex(8L), toCloudPosition(split.getAcceptedPosition()));

              // Check that the progress has been recomputed.
              ApproximateReportedProgress progress =
                  readerProgressToCloudProgress(readOperation.getProgress());
              assertEquals(1, progress.getPosition().getRecordIndex().longValue());
            } else if ("3".equals(elem)) {
              // Should accept a split at an earlier position than previously requested.
              // Should reject a split at a later position than previously requested.
              // Note that here we're testing our own MockReaderIterator class, so it's
              // kind of pointless, but we're also testing that ReadOperation correctly
              // relays the request to the iterator.
              NativeReader.DynamicSplitResultWithPosition split =
                  (NativeReader.DynamicSplitResultWithPosition)
                      readOperation.requestDynamicSplit(splitRequestAtIndex(6L));
              assertNotNull(split);
              assertEquals(positionAtIndex(6L), toCloudPosition(split.getAcceptedPosition()));
              split =
                  (NativeReader.DynamicSplitResultWithPosition)
                      readOperation.requestDynamicSplit(splitRequestAtIndex(6L));
              assertNull(split);
            }
          }
        };
    ReadOperation readOperation = ReadOperation.forTest(reader, receiver, context);
    readOperation.setProgressUpdatePeriodMs(ReadOperation.UPDATE_ON_EACH_ITERATION);
    operationHolder[0] = readOperation;

    // An unstarted ReadOperation refuses split requests.
    assertNull(readOperation.requestDynamicSplit(splitRequestAtIndex(8L)));

    readOperation.start();
    readOperation.finish();

    // Operation is now finished. Check that it refuses a split request.
    assertNull(readOperation.requestDynamicSplit(splitRequestAtIndex(5L)));
  }

  @Test
  public void testDynamicSplitDoesNotBlock() throws Exception {
    MockReaderIterator iterator = new MockReaderIterator(0, 10);
    MockOutputReceiver receiver = new MockOutputReceiver();
    ReadOperation readOperation =
        ReadOperation.forTest(new MockReader(iterator), receiver, context);

    Thread thread = runReadLoopInThread(readOperation);
    iterator.offerNext(0);
    receiver.unblockProcess();
    // Read loop is blocked in next(). Do not offer another next item,
    // but check that we can still split while the read loop is blocked.
    NativeReader.DynamicSplitResultWithPosition split =
        (NativeReader.DynamicSplitResultWithPosition)
            readOperation.requestDynamicSplit(splitRequestAtIndex(5L));
    assertNotNull(split);
    assertEquals(positionAtIndex(5L), toCloudPosition(split.getAcceptedPosition()));

    for (int i = 1; i < 5; ++i) {
      iterator.offerNext(i);
      receiver.unblockProcess();
    }

    thread.join();
  }

  @Test
  public void testRaceBetweenCloseAndDynamicSplit() throws Exception {
    InMemoryReader<String> reader =
        new InMemoryReader<>(Arrays.asList("a", "b", "c", "d", "e"), 0, 5, StringUtf8Coder.of());
    TestOutputReceiver receiver =
        new TestOutputReceiver(StringUtf8Coder.of(), NameContextsForTests.nameContextForTest());
    final ReadOperation readOperation = ReadOperation.forTest(reader, receiver, context);

    readOperation.start();
    // Check that requestDynamicSplit is safe (no-op) if the operation is done with start()
    // but not yet done with finish()
    readOperation.requestDynamicSplit(splitRequestAtIndex(5L));
    readOperation.finish();

    // Check once more that requestDynamicSplit on a finished operation is also safe (no-op).
    readOperation.requestDynamicSplit(splitRequestAtIndex(5L));
  }

  @Test
  public void testAbortBetweenStartAndFinish() throws Exception {
    MockOutputReceiver receiver = new MockOutputReceiver();
    TestReader reader = new TestReader();
    ReadOperation op = ReadOperation.forTest(reader, receiver, context);

    op.start();
    op.abort();
    assertTrue(reader.aborted);
  }

  @Test
  public void testAbortAfterFinish() throws Exception {
    MockOutputReceiver receiver = new MockOutputReceiver();
    TestReader reader = new TestReader();
    ReadOperation op = ReadOperation.forTest(reader, receiver, context);

    op.start();
    op.finish();
    op.abort();

    assertTrue(reader.closed);
    assertTrue(reader.aborted);
  }

  private Thread runReadLoopInThread(final ReadOperation readOperation) {
    Thread thread =
        new Thread(
            () -> {
              try {
                readOperation.start();
                readOperation.finish();
              } catch (Exception e) {
                throw new RuntimeException(e);
              }
            });
    thread.start();
    return thread;
  }

  private static class MockReaderIterator extends NativeReader.NativeReaderIterator<Integer> {
    private final OffsetRangeTracker tracker;
    private Exchanger<Integer> exchanger = new Exchanger<>();
    private int current;
    private volatile boolean isClosed;
    private boolean signalBlockedInAdvance = false;
    private CyclicBarrier blockedInAdvanceBarrier =
        new CyclicBarrier(2 /* test thread and loop thread */);

    public MockReaderIterator(int from, int to) {
      this.tracker = new OffsetRangeTracker(from, to);
      this.current = from - 1;
    }

    @Override
    public boolean start() throws IOException {
      return advance();
    }

    /**
     * Not thread safe. Clients should avoid threads concurrently calling this method and
     * blockInNextAdvance, unless the thread in advance is blocked in or leaving exchangeCurrent.
     */
    @Override
    public boolean advance() throws IOException {
      if (!tracker.tryReturnRecordAt(true, current + 1)) {
        return false;
      }
      ++current;
      if (signalBlockedInAdvance) {
        signalBlockedInAdvance = false;
        try {
          blockedInAdvanceBarrier.await();
        } catch (InterruptedException | BrokenBarrierException e) {
          throw new RuntimeException(e);
        }
      }
      exchangeCurrent();
      return true;
    }

    private void exchangeCurrent() {
      try {
        current = exchanger.exchange(current);
      } catch (InterruptedException e) {
        throw new NoSuchElementException("interrupted");
      }
    }

    @Override
    public Integer getCurrent() {
      return current;
    }

    @Override
    public NativeReader.Progress getProgress() {
      Preconditions.checkState(!isClosed);
      return cloudProgressToReaderProgress(
          new ApproximateReportedProgress()
              .setPosition(new Position().setRecordIndex((long) current))
              .setFractionConsumed(tracker.getFractionConsumed()));
    }

    @Override
    public NativeReader.DynamicSplitResult requestCheckpoint() {
      Preconditions.checkState(!isClosed);
      if (!tracker.trySplitAtPosition(current + 1)) {
        return null;
      }
      return new NativeReader.DynamicSplitResultWithPosition(
          cloudPositionToReaderPosition(positionAtIndex(current + 1L)));
    }

    @Override
    public NativeReader.DynamicSplitResult requestDynamicSplit(
        NativeReader.DynamicSplitRequest splitRequest) {
      Preconditions.checkState(!isClosed);
      ApproximateSplitRequest approximateSplitRequest =
          splitRequestToApproximateSplitRequest(splitRequest);
      int index = approximateSplitRequest.getPosition().getRecordIndex().intValue();
      if (!tracker.trySplitAtPosition(index)) {
        return null;
      }
      return new NativeReader.DynamicSplitResultWithPosition(
          cloudPositionToReaderPosition(approximateSplitRequest.getPosition()));
    }

    public int offerNext(int next) {
      try {
        return exchanger.exchange(next);
      } catch (InterruptedException e) {
        throw new RuntimeException(e);
      }
    }

    /**
     * Not thread safe. Clients should avoid threads concurrently calling this method and advance,
     * unless the thread in advance is blocked in or leaving exchangeCurrent.
     */
    public void blockInNextAdvance() {
      signalBlockedInAdvance = true;
    }

    public void awaitBlockedInAdvance() {
      try {
        blockedInAdvanceBarrier.await();
      } catch (InterruptedException | BrokenBarrierException e) {
        throw new RuntimeException("interrupted");
      }
    }

    @Override
    public void close() throws IOException {
      isClosed = true;
    }
  }

  private static class MockReader extends NativeReader<Integer> {
    private NativeReaderIterator<Integer> iterator;

    private MockReader(NativeReaderIterator<Integer> iterator) {
      this.iterator = iterator;
    }

    @Override
    public NativeReaderIterator<Integer> iterator() throws IOException {
      return iterator;
    }
  }

  /** A mock {@link OutputReceiver} that blocks the read loop in {@link ReadOperation}. */
  private static class MockOutputReceiver extends OutputReceiver {
    private Exchanger<Object> exchanger = new Exchanger<>();

    @Override
    public void process(Object elem) throws Exception {
      exchanger.exchange(null);
    }

    public void unblockProcess() {
      try {
        exchanger.exchange(null);
      } catch (InterruptedException e) {
        throw new RuntimeException(e);
      }
    }
  }
}
