/*
 * 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;

import static org.apache.beam.runners.dataflow.worker.SourceTranslationUtils.readerProgressToCloudProgress;
import static org.apache.beam.runners.dataflow.worker.SourceTranslationUtils.toDynamicSplitRequest;
import static org.apache.beam.sdk.util.CoderUtils.encodeToByteArray;
import static org.apache.beam.sdk.util.StringUtils.byteArrayToJsonString;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertFalse;
import static org.junit.Assert.assertNull;
import static org.junit.Assert.assertTrue;

import com.google.api.services.dataflow.model.ApproximateSplitRequest;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import javax.annotation.Nullable;
import org.apache.beam.runners.dataflow.worker.util.common.worker.ExecutorTestUtils;
import org.apache.beam.runners.dataflow.worker.util.common.worker.NativeReader;
import org.apache.beam.sdk.coders.BigEndianIntegerCoder;
import org.apache.beam.sdk.coders.Coder;
import org.junit.Assert;
import org.junit.Rule;
import org.junit.Test;
import org.junit.rules.ExpectedException;
import org.junit.runner.RunWith;
import org.junit.runners.JUnit4;

/** Tests for InMemoryReader. */
@RunWith(JUnit4.class)
public class InMemoryReaderTest {
  @Rule public ExpectedException expectedException = ExpectedException.none();

  static <T> List<String> encodedElements(List<T> elements, Coder<T> coder) throws Exception {
    List<String> encodedElements = new ArrayList<>();
    for (T element : elements) {
      byte[] encodedElement = encodeToByteArray(coder, element);
      String encodedElementString = byteArrayToJsonString(encodedElement);
      encodedElements.add(encodedElementString);
    }
    return encodedElements;
  }

  <T> void runTestReadInMemory(
      List<T> elements,
      @Nullable Integer startIndex,
      @Nullable Integer endIndex,
      List<T> expectedElements,
      List<Integer> expectedSizes,
      Coder<T> coder)
      throws Exception {
    InMemoryReader<T> inMemoryReader =
        new InMemoryReader<>(encodedElements(elements, coder), startIndex, endIndex, coder);
    ExecutorTestUtils.TestReaderObserver observer =
        new ExecutorTestUtils.TestReaderObserver(inMemoryReader);
    List<T> actualElements = new ArrayList<>();
    try (InMemoryReader<T>.InMemoryReaderIterator iterator = inMemoryReader.iterator()) {
      for (long i = inMemoryReader.startIndex;
          (i == inMemoryReader.startIndex) ? iterator.start() : iterator.advance();
          i++) {
        Assert.assertEquals(
            ReaderTestUtils.approximateProgressAtIndex(i),
            readerProgressToCloudProgress(iterator.getProgress()));
        actualElements.add(iterator.getCurrent());
      }
    }
    assertEquals(expectedElements, actualElements);
    assertEquals(expectedSizes, observer.getActualSizes());
  }

  @Test
  public void testReadAllElements() throws Exception {
    runTestReadInMemory(
        Arrays.asList(33, 44, 55, 66, 77, 88),
        null,
        null,
        Arrays.asList(33, 44, 55, 66, 77, 88),
        Arrays.asList(4, 4, 4, 4, 4, 4),
        BigEndianIntegerCoder.of());
  }

  @Test
  public void testReadElementsFromStart() throws Exception {
    runTestReadInMemory(
        Arrays.asList(33, 44, 55, 66, 77, 88),
        2,
        null,
        Arrays.asList(55, 66, 77, 88),
        Arrays.asList(4, 4, 4, 4),
        BigEndianIntegerCoder.of());
  }

  @Test
  public void testReadElementsToEnd() throws Exception {
    runTestReadInMemory(
        Arrays.asList(33, 44, 55, 66, 77, 88),
        null,
        3,
        Arrays.asList(33, 44, 55),
        Arrays.asList(4, 4, 4),
        BigEndianIntegerCoder.of());
  }

  @Test
  public void testReadElementsFromStartToEnd() throws Exception {
    runTestReadInMemory(
        Arrays.asList(33, 44, 55, 66, 77, 88),
        2,
        5,
        Arrays.asList(55, 66, 77),
        Arrays.asList(4, 4, 4),
        BigEndianIntegerCoder.of());
  }

  @Test
  public void testReadElementsOffEnd() throws Exception {
    runTestReadInMemory(
        Arrays.asList(33, 44, 55, 66, 77, 88),
        null,
        30,
        Arrays.asList(33, 44, 55, 66, 77, 88),
        Arrays.asList(4, 4, 4, 4, 4, 4),
        BigEndianIntegerCoder.of());
  }

  @Test
  public void testReadElementsFromStartPastEnd() throws Exception {
    runTestReadInMemory(
        Arrays.asList(33, 44, 55, 66, 77, 88),
        20,
        null,
        Arrays.<Integer>asList(),
        Arrays.<Integer>asList(),
        BigEndianIntegerCoder.of());
  }

  @Test
  public void testReadElementsFromStartToEndEmptyRange() throws Exception {
    runTestReadInMemory(
        Arrays.asList(33, 44, 55, 66, 77, 88),
        2,
        2,
        Arrays.<Integer>asList(),
        Arrays.<Integer>asList(),
        BigEndianIntegerCoder.of());
  }

  @Test
  public void testReadNoElements() throws Exception {
    runTestReadInMemory(
        Arrays.<Integer>asList(),
        null,
        null,
        Arrays.<Integer>asList(),
        Arrays.<Integer>asList(),
        BigEndianIntegerCoder.of());
  }

  @Test
  public void testReadNoElementsFromStartToEndEmptyRange() throws Exception {
    runTestReadInMemory(
        Arrays.<Integer>asList(),
        0,
        0,
        Arrays.<Integer>asList(),
        Arrays.<Integer>asList(),
        BigEndianIntegerCoder.of());
  }

  @Test
  public void testProgressReporting() throws Exception {
    List<Integer> elements = Arrays.asList(33, 44, 55, 66, 77, 88);
    // Should initially read elements at indices: 44@1, 55@2, 66@3, 77@4

    Coder<Integer> coder = BigEndianIntegerCoder.of();
    InMemoryReader<Integer> inMemoryReader =
        new InMemoryReader<>(encodedElements(elements, coder), 1, 4, coder);
    try (InMemoryReader<Integer>.InMemoryReaderIterator iterator = inMemoryReader.iterator()) {
      assertNull(iterator.getProgress());
      assertEquals(3, iterator.getRemainingParallelism(), 0.0);

      assertTrue(iterator.start());
      Assert.assertEquals(
          ReaderTestUtils.positionAtIndex(1L),
          ReaderTestUtils.positionFromProgress(iterator.getProgress()));
      assertEquals(3, iterator.getRemainingParallelism(), 0.0);

      assertTrue(iterator.advance());
      Assert.assertEquals(
          ReaderTestUtils.positionAtIndex(2L),
          ReaderTestUtils.positionFromProgress(iterator.getProgress()));
      assertEquals(2, iterator.getRemainingParallelism(), 0.0);

      assertTrue(iterator.advance());
      Assert.assertEquals(
          ReaderTestUtils.positionAtIndex(3L),
          ReaderTestUtils.positionFromProgress(iterator.getProgress()));
      assertEquals(1, iterator.getRemainingParallelism(), 0.0);

      assertFalse(iterator.advance());
    }
  }

  @Test
  public void testDynamicSplit() throws Exception {
    List<Integer> elements = Arrays.asList(33, 44, 55, 66, 77, 88);
    // Should initially read elements at indices: 44@1, 55@2, 66@3, 77@4

    Coder<Integer> coder = BigEndianIntegerCoder.of();
    InMemoryReader<Integer> inMemoryReader =
        new InMemoryReader<>(encodedElements(elements, coder), 1, 4, coder);

    // Unstarted iterator.
    try (InMemoryReader<Integer>.InMemoryReaderIterator iterator = inMemoryReader.iterator()) {
      assertNull(iterator.requestDynamicSplit(ReaderTestUtils.splitRequestAtIndex(3L)));
    }

    // Illegal proposed split position.
    try (InMemoryReader<Integer>.InMemoryReaderIterator iterator = inMemoryReader.iterator()) {
      assertNull(iterator.requestDynamicSplit(ReaderTestUtils.splitRequestAtIndex(3L)));
      // Poke the iterator so that we can test dynamic splitting.
      assertTrue(iterator.start());
      assertNull(
          iterator.requestDynamicSplit(toDynamicSplitRequest(new ApproximateSplitRequest())));
      assertNull(iterator.requestDynamicSplit(ReaderTestUtils.splitRequestAtIndex(null)));
    }

    // Successful update.
    try (InMemoryReader<Integer>.InMemoryReaderIterator iterator = inMemoryReader.iterator()) {
      // Poke the iterator so that we can test dynamic splitting.
      assertTrue(iterator.start());
      NativeReader.DynamicSplitResult dynamicSplitResult =
          iterator.requestDynamicSplit(ReaderTestUtils.splitRequestAtIndex(3L));
      Assert.assertEquals(
          ReaderTestUtils.positionAtIndex(3L),
          ReaderTestUtils.positionFromSplitResult(dynamicSplitResult));
      assertEquals(3, iterator.tracker.getStopPosition().longValue());
      assertEquals(44, iterator.getCurrent().intValue());
      assertTrue(iterator.advance());
      assertEquals(55, iterator.getCurrent().intValue());
      assertFalse(iterator.advance());
    }

    // Proposed split position is before the current position, no update.
    try (InMemoryReader<Integer>.InMemoryReaderIterator iterator = inMemoryReader.iterator()) {
      // Poke the iterator so that we can test dynamic splitting.
      assertTrue(iterator.start());
      assertEquals(44, iterator.getCurrent().intValue());
      assertTrue(iterator.advance());
      assertEquals(55, iterator.getCurrent().intValue());
      assertTrue(iterator.advance()); // Returns true => we promised to return 66.
      // Now we have to refuse the split.
      assertNull(iterator.requestDynamicSplit(ReaderTestUtils.splitRequestAtIndex(3L)));
      assertEquals(4, iterator.tracker.getStopPosition().longValue());
      assertEquals(66, iterator.getCurrent().intValue());
      assertFalse(iterator.advance());
    }

    // Proposed split position is after the current stop (end) position, no update.
    try (InMemoryReader<Integer>.InMemoryReaderIterator iterator = inMemoryReader.iterator()) {
      // Poke the iterator so that we can test dynamic splitting.
      assertTrue(iterator.start());
      assertNull(iterator.requestDynamicSplit(ReaderTestUtils.splitRequestAtIndex(5L)));
      assertEquals(4, iterator.tracker.getStopPosition().longValue());
    }
  }

  @Test
  public void testParallelism() throws Exception {
    List<Integer> elements = Arrays.asList(33, 44, 55, 66, 77, 88);

    Coder<Integer> coder = BigEndianIntegerCoder.of();
    InMemoryReader<Integer> inMemoryReader =
        new InMemoryReader<>(encodedElements(elements, coder), 1, 4, coder);
    int count = 0;
    try (InMemoryReader<Integer>.InMemoryReaderIterator iterator = inMemoryReader.iterator()) {
      for (boolean more = iterator.start(); more; more = iterator.advance()) {
        assertTrue(iterator.getRemainingParallelism() >= 1);
        assertEquals(3 - count, iterator.getRemainingParallelism(), 0 /*tolerance*/);
        count++;
      }
    }
  }
}
