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   * 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.
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  package org.apache.beam.sdk.transforms;
  
  import static org.junit.Assert.assertEquals;
  import static org.junit.Assert.assertTrue;
  
  import java.util.ArrayList;
  import java.util.Comparator;
  import java.util.List;
  import java.util.stream.Collectors;
  import org.apache.beam.sdk.io.range.OffsetRange;
  import org.apache.beam.sdk.testing.NeedsRunner;
  import org.apache.beam.sdk.testing.PAssert;
  import org.apache.beam.sdk.testing.TestPipeline;
  import org.apache.beam.sdk.testing.UsesImpulse;
  import org.apache.beam.sdk.testing.UsesStatefulParDo;
  import org.apache.beam.sdk.testing.UsesUnboundedPCollections;
  import org.apache.beam.sdk.testing.UsesUnboundedSplittableParDo;
  import org.apache.beam.sdk.transforms.windowing.FixedWindows;
  import org.apache.beam.sdk.transforms.windowing.TimestampCombiner;
  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.TypeDescriptor;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.collect.Iterables;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.collect.Streams;
  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 PeriodicSequence. */
  @RunWith(JUnit4.class)
  public class PeriodicSequenceTest {
    @Rule public transient TestPipeline p = TestPipeline.create();
  
    public static class ExtractTsDoFn<InputT>
        extends DoFn<InputT, TimestampedValue<KV<InputT, Instant>>> {
  
      @ProcessElement
      public void processElement(
          @Element InputT element,
          @Timestamp Instant ts,
          OutputReceiver<TimestampedValue<KV<InputT, Instant>>> output)
          throws Exception {
  
        output.output(TimestampedValue.of(KV.of(element, ts), Instant.now()));
      }
    }
  
    @Test
    @Category({
      NeedsRunner.class,
      UsesImpulse.class,
      UsesStatefulParDo.class,
      UsesUnboundedPCollections.class,
      UsesUnboundedSplittableParDo.class
    })
    public void testOutputsProperElements() {
      Instant startTime = Instant.now().plus(Duration.standardSeconds(2));
      Duration interval = Duration.millis(250);
      long intervalMillis = interval.getMillis();
      long duration = 3 * intervalMillis;
      Instant stopTime = startTime.plus(Duration.millis(duration));
  
      PCollection<TimestampedValue<KV<Instant, Instant>>> result =
          p.apply(Create.of(new PeriodicSequence.SequenceDefinition(startTime, stopTime, interval)))
              .apply(PeriodicSequence.create())
              .apply(
                  Window.<Instant>into(FixedWindows.of(interval))
                      .withTimestampCombiner(TimestampCombiner.EARLIEST))
              .apply(WithKeys.of("dummy"))
              .apply(GroupByKey.create())
              .apply(
                  MapElements.into(TypeDescriptor.of(Instant.class))
                      .via(e -> Iterables.getOnlyElement(e.getValue())))
              .apply(ParDo.of(new ExtractTsDoFn<>())); // validate timestamps
  
      ArrayList<Instant> expectedResults = new ArrayList<>();
      for (long i = 0; i <= duration; i += intervalMillis) {
        Instant el = startTime.plus(Duration.millis(i));
        expectedResults.add(el);
      }
  
      PAssert.that(result)
          .satisfies(
              values -> {
                List<TimestampedValue<KV<Instant, Instant>>> sortedValues =
                    Streams.stream(values)
                        .sorted(Comparator.comparing(e -> e.getValue().getValue()))
                        .collect(Collectors.toList());
  
                assertEquals(
                    expectedResults,
                    sortedValues.stream()
                        .map(e -> e.getValue().getValue())
                        .collect(Collectors.toList()));
  
                Instant minTs =
                    sortedValues.stream()
                        .min(Comparator.comparing(TimestampedValue::getTimestamp))
                        .get()
                        .getTimestamp();
                Instant maxTs =
                    sortedValues.stream()
                        .max(Comparator.comparing(TimestampedValue::getTimestamp))
                        .get()
                        .getTimestamp();
                final long expectedDiff = intervalMillis / 2;
                assertTrue(
                    String.format(
                        "Expected processing-time diff at least %d, got %d",
                        expectedDiff, maxTs.getMillis() - minTs.getMillis()),
                    maxTs.getMillis() - minTs.getMillis() > expectedDiff);
                return null;
              });
  
      p.run().waitUntilFinish();
    }
  
    @Test
    public void testBacklogBytes() {
      assertEquals(
          0, PeriodicSequence.sequenceBacklogBytes(10, 100, new OffsetRange(100, Long.MAX_VALUE)));
      assertEquals(
          8, PeriodicSequence.sequenceBacklogBytes(10, 100, new OffsetRange(90, Long.MAX_VALUE)));
      assertEquals(
          0, PeriodicSequence.sequenceBacklogBytes(10, 100, new OffsetRange(91, Long.MAX_VALUE)));
      assertEquals(
          8, PeriodicSequence.sequenceBacklogBytes(10, 100, new OffsetRange(89, Long.MAX_VALUE)));
      assertEquals(
          16, PeriodicSequence.sequenceBacklogBytes(10, 101, new OffsetRange(81, Long.MAX_VALUE)));
      assertEquals(
          8 * 10000 / 100,
          PeriodicSequence.sequenceBacklogBytes(100, 10000, new OffsetRange(0, Long.MAX_VALUE)));
      assertEquals(
          0, PeriodicSequence.sequenceBacklogBytes(10, 10000, new OffsetRange(10011, 10025)));
      assertEquals(
          8, PeriodicSequence.sequenceBacklogBytes(10, 10100, new OffsetRange(10011, 10025)));
    }
  }
  