/*
 * 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.sdk.transforms;

import static org.apache.beam.sdk.TestUtils.KvMatcher.isKv;
import static org.hamcrest.Matchers.equalTo;
import static org.hamcrest.collection.IsIterableContainingInAnyOrder.containsInAnyOrder;
import static org.hamcrest.core.Is.is;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertThat;

import com.google.common.collect.ImmutableList;
import java.io.Serializable;
import org.apache.beam.sdk.coders.KvCoder;
import org.apache.beam.sdk.coders.StringUtf8Coder;
import org.apache.beam.sdk.coders.VarIntCoder;
import org.apache.beam.sdk.coders.VarLongCoder;
import org.apache.beam.sdk.testing.PAssert;
import org.apache.beam.sdk.testing.TestPipeline;
import org.apache.beam.sdk.testing.TestStream;
import org.apache.beam.sdk.testing.UsesTestStream;
import org.apache.beam.sdk.testing.ValidatesRunner;
import org.apache.beam.sdk.transforms.windowing.BoundedWindow;
import org.apache.beam.sdk.transforms.windowing.FixedWindows;
import org.apache.beam.sdk.transforms.windowing.GlobalWindow;
import org.apache.beam.sdk.transforms.windowing.Sessions;
import org.apache.beam.sdk.transforms.windowing.Window;
import org.apache.beam.sdk.values.KV;
import org.apache.beam.sdk.values.PCollection;
import org.apache.beam.sdk.values.TimestampedValue;
import org.apache.beam.sdk.values.TypeDescriptors;
import org.apache.beam.sdk.values.WindowingStrategy;
import org.joda.time.Duration;
import org.joda.time.Instant;
import org.junit.Rule;
import org.junit.Test;
import org.junit.experimental.categories.Category;
import org.junit.runner.RunWith;
import org.junit.runners.JUnit4;

/**
 * Tests for {@link Reshuffle}.
 */
@RunWith(JUnit4.class)
public class ReshuffleTest implements Serializable {

  private static final ImmutableList<KV<String, Integer>> ARBITRARY_KVS = ImmutableList.of(
        KV.of("k1", 3),
        KV.of("k5", Integer.MAX_VALUE),
        KV.of("k5", Integer.MIN_VALUE),
        KV.of("k2", 66),
        KV.of("k1", 4),
        KV.of("k2", -33),
        KV.of("k3", 0));

  // TODO: test with more than one value per key
  private static final ImmutableList<KV<String, Integer>> GBK_TESTABLE_KVS = ImmutableList.of(
        KV.of("k1", 3),
        KV.of("k2", 4));

  private static class AssertThatHasExpectedContents
      implements SerializableFunction<Iterable<KV<String, Iterable<Integer>>>, Void> {
    @Override
    public Void apply(Iterable<KV<String, Iterable<Integer>>> actual) {
      assertThat(actual, containsInAnyOrder(
          isKv(is("k1"), containsInAnyOrder(3)),
          isKv(is("k2"), containsInAnyOrder(4))));
      return null;
    }
  }

  @Rule
  public final transient TestPipeline pipeline = TestPipeline.create();

  @Test
  @Category(ValidatesRunner.class)
  public void testJustReshuffle() {

    PCollection<KV<String, Integer>> input = pipeline
        .apply(Create.of(ARBITRARY_KVS)
            .withCoder(KvCoder.of(StringUtf8Coder.of(), VarIntCoder.of())));

    PCollection<KV<String, Integer>> output = input.apply(Reshuffle.of());

    PAssert.that(output).containsInAnyOrder(ARBITRARY_KVS);

    assertEquals(
        input.getWindowingStrategy(),
        output.getWindowingStrategy());

    pipeline.run();
  }

  /**
   * Tests that timestamps are preserved after applying a {@link Reshuffle} with the default
   * {@link WindowingStrategy}.
   */
  @Test
  @Category(ValidatesRunner.class)
  public void testReshufflePreservesTimestamps() {
    PCollection<KV<String, TimestampedValue<String>>> input =
        pipeline
            .apply(
                Create.timestamped(
                        TimestampedValue.of("foo", BoundedWindow.TIMESTAMP_MIN_VALUE),
                        TimestampedValue.of("foo", new Instant(0)),
                        TimestampedValue.of("bar", new Instant(33)),
                        TimestampedValue.of("bar", GlobalWindow.INSTANCE.maxTimestamp()))
                    .withCoder(StringUtf8Coder.of()))
            .apply(
                WithKeys.<String, String>of(input12 -> input12)
                    .withKeyType(TypeDescriptors.strings()))
            .apply("ReifyOriginalTimestamps", Reify.timestampsInValue());

    // The outer TimestampedValue is the reified timestamp post-reshuffle. The inner
    // TimestampedValue is the pre-reshuffle timestamp.
    PCollection<TimestampedValue<TimestampedValue<String>>> output =
        input
            .apply(Reshuffle.of())
            .apply("ReifyReshuffledTimestamps", Reify.timestampsInValue())
            .apply(Values.create());

    PAssert.that(output)
        .satisfies(
            input1 -> {
              for (TimestampedValue<TimestampedValue<String>> elem : input1) {
                Instant originalTimestamp = elem.getValue().getTimestamp();
                Instant afterReshuffleTimestamp = elem.getTimestamp();
                assertThat(
                    "Reshuffle must preserve element timestamps",
                    afterReshuffleTimestamp,
                    equalTo(originalTimestamp));
              }
              return null;
            });

    pipeline.run();
  }

  @Test
  @Category(ValidatesRunner.class)
  public void testReshuffleAfterSessionsAndGroupByKey() {

    PCollection<KV<String, Iterable<Integer>>> input =
        pipeline
            .apply(
                Create.of(GBK_TESTABLE_KVS)
                    .withCoder(KvCoder.of(StringUtf8Coder.of(), VarIntCoder.of())))
            .apply(Window.into(Sessions.withGapDuration(Duration.standardMinutes(10))))
            .apply(GroupByKey.create());

    PCollection<KV<String, Iterable<Integer>>> output = input.apply(Reshuffle.of());

    PAssert.that(output).satisfies(new AssertThatHasExpectedContents());

    assertEquals(
        input.getWindowingStrategy(),
        output.getWindowingStrategy());

    pipeline.run();
  }

  @Test
  @Category(ValidatesRunner.class)
  public void testReshuffleAfterFixedWindowsAndGroupByKey() {

    PCollection<KV<String, Iterable<Integer>>> input =
        pipeline
            .apply(
                Create.of(GBK_TESTABLE_KVS)
                    .withCoder(KvCoder.of(StringUtf8Coder.of(), VarIntCoder.of())))
            .apply(Window.into(FixedWindows.of(Duration.standardMinutes(10L))))
            .apply(GroupByKey.create());

    PCollection<KV<String, Iterable<Integer>>> output = input.apply(Reshuffle.of());

    PAssert.that(output).satisfies(new AssertThatHasExpectedContents());

    assertEquals(
        input.getWindowingStrategy(),
        output.getWindowingStrategy());

    pipeline.run();
  }

  @Test
  @Category(ValidatesRunner.class)
  public void testReshuffleAfterSlidingWindowsAndGroupByKey() {

    PCollection<KV<String, Iterable<Integer>>> input =
        pipeline
            .apply(
                Create.of(GBK_TESTABLE_KVS)
                    .withCoder(KvCoder.of(StringUtf8Coder.of(), VarIntCoder.of())))
            .apply(Window.into(FixedWindows.of(Duration.standardMinutes(10L))))
            .apply(GroupByKey.create());

    PCollection<KV<String, Iterable<Integer>>> output = input.apply(Reshuffle.of());

    PAssert.that(output).satisfies(new AssertThatHasExpectedContents());

    assertEquals(
        input.getWindowingStrategy(),
        output.getWindowingStrategy());

    pipeline.run();
  }

  @Test
  @Category(ValidatesRunner.class)
  public void testReshuffleAfterFixedWindows() {

    PCollection<KV<String, Integer>> input =
        pipeline
            .apply(
                Create.of(ARBITRARY_KVS)
                    .withCoder(KvCoder.of(StringUtf8Coder.of(), VarIntCoder.of())))
            .apply(Window.into(FixedWindows.of(Duration.standardMinutes(10L))));

    PCollection<KV<String, Integer>> output = input.apply(Reshuffle.of());

    PAssert.that(output).containsInAnyOrder(ARBITRARY_KVS);

    assertEquals(
        input.getWindowingStrategy(),
        output.getWindowingStrategy());

    pipeline.run();
  }


  @Test
  @Category(ValidatesRunner.class)
  public void testReshuffleAfterSlidingWindows() {

    PCollection<KV<String, Integer>> input =
        pipeline
            .apply(
                Create.of(ARBITRARY_KVS)
                    .withCoder(KvCoder.of(StringUtf8Coder.of(), VarIntCoder.of())))
            .apply(Window.into(FixedWindows.of(Duration.standardMinutes(10L))));

    PCollection<KV<String, Integer>> output = input.apply(Reshuffle.of());

    PAssert.that(output).containsInAnyOrder(ARBITRARY_KVS);

    assertEquals(
        input.getWindowingStrategy(),
        output.getWindowingStrategy());

    pipeline.run();
  }

  @Test
  @Category({ValidatesRunner.class, UsesTestStream.class})
  public void testReshuffleWithTimestampsStreaming() {
    TestStream<Long> stream =
        TestStream.create(VarLongCoder.of())
            .advanceWatermarkTo(new Instant(0L).plus(Duration.standardDays(48L)))
            .addElements(
                TimestampedValue.of(0L, new Instant(0L)),
                TimestampedValue.of(1L, new Instant(0L).plus(Duration.standardDays(48L))),
                TimestampedValue.of(
                    2L, BoundedWindow.TIMESTAMP_MAX_VALUE.minus(Duration.standardDays(48L))))
            .advanceWatermarkToInfinity();
    PCollection<KV<String, Long>> input =
        pipeline
            .apply(stream)
            .apply(WithKeys.of(""))
            .apply(Window.into(FixedWindows.of(Duration.standardMinutes(10L))));

    PCollection<KV<String, Long>> reshuffled = input.apply(Reshuffle.of());
    PAssert.that(reshuffled.apply(Values.create())).containsInAnyOrder(0L, 1L, 2L);

    pipeline.run();
  }
}
