content: /*
   * 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.LINES;
  import static org.apache.beam.sdk.TestUtils.LINES2;
  import static org.apache.beam.sdk.TestUtils.LINES_ARRAY;
  import static org.apache.beam.sdk.TestUtils.NO_LINES;
  import static org.apache.beam.sdk.TestUtils.NO_LINES_ARRAY;
  import static org.hamcrest.MatcherAssert.assertThat;
  import static org.hamcrest.Matchers.equalTo;
  import static org.hamcrest.Matchers.not;
  
  import java.io.Serializable;
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.Collection;
  import java.util.List;
  import java.util.Set;
  import org.apache.beam.sdk.Pipeline;
  import org.apache.beam.sdk.coders.BigEndianLongCoder;
  import org.apache.beam.sdk.coders.CannotProvideCoderException;
  import org.apache.beam.sdk.coders.Coder;
  import org.apache.beam.sdk.coders.CollectionCoder;
  import org.apache.beam.sdk.coders.IterableCoder;
  import org.apache.beam.sdk.coders.KvCoder;
  import org.apache.beam.sdk.coders.ListCoder;
  import org.apache.beam.sdk.coders.NullableCoder;
  import org.apache.beam.sdk.coders.SerializableCoder;
  import org.apache.beam.sdk.coders.SetCoder;
  import org.apache.beam.sdk.coders.StringUtf8Coder;
  import org.apache.beam.sdk.coders.VarLongCoder;
  import org.apache.beam.sdk.coders.VoidCoder;
  import org.apache.beam.sdk.io.GenerateSequence;
  import org.apache.beam.sdk.testing.FlattenWithHeterogeneousCoders;
  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.UsesSideInputs;
  import org.apache.beam.sdk.testing.ValidatesRunner;
  import org.apache.beam.sdk.transforms.windowing.FixedWindows;
  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.PCollectionList;
  import org.apache.beam.sdk.values.PCollectionTuple;
  import org.apache.beam.sdk.values.PCollectionView;
  import org.apache.beam.sdk.values.TupleTag;
  import org.apache.beam.sdk.values.TupleTagList;
  import org.apache.beam.sdk.values.TypeDescriptor;
  import org.apache.beam.sdk.values.TypeDescriptors;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.collect.ImmutableSet;
  import org.joda.time.Duration;
  import org.junit.Assert;
  import org.junit.Rule;
  import org.junit.Test;
  import org.junit.experimental.categories.Category;
  import org.junit.rules.ExpectedException;
  import org.junit.rules.Timeout;
  import org.junit.runner.RunWith;
  import org.junit.runners.JUnit4;
  
  /** Tests for Flatten. */
  @RunWith(JUnit4.class)
  public class FlattenTest implements Serializable {
  
    @Rule public final transient TestPipeline p = TestPipeline.create();
  
    @Rule public transient ExpectedException thrown = ExpectedException.none();
  
    @Rule public transient Timeout globalTimeout = Timeout.seconds(1200);
  
    private static class ClassWithoutCoder {}
  
    @Test
    @Category(ValidatesRunner.class)
    public void testFlattenPCollections() {
      List<List<String>> inputs = Arrays.asList(LINES, NO_LINES, LINES2, NO_LINES, LINES, NO_LINES);
  
      PCollection<String> output =
          makePCollectionListOfStrings(p, inputs).apply(Flatten.pCollections());
  
      PAssert.that(output).containsInAnyOrder(flattenLists(inputs));
      p.run();
    }
  
    @Test
    @Category(ValidatesRunner.class)
    public void testFlattenPCollectionsSingletonList() {
      PCollection<String> input = p.apply(Create.of(LINES));
      PCollection<String> output = PCollectionList.of(input).apply(Flatten.pCollections());
  
      assertThat(output, not(equalTo(input)));
  
      PAssert.that(output).containsInAnyOrder(LINES);
      p.run();
    }
  
    @Test
    @Category(ValidatesRunner.class)
    public void testFlattenPCollectionsThenParDo() {
      List<List<String>> inputs = Arrays.asList(LINES, NO_LINES, LINES2, NO_LINES, LINES, NO_LINES);
  
      PCollection<String> output =
          makePCollectionListOfStrings(p, inputs)
              .apply(Flatten.pCollections())
              .apply(ParDo.of(new IdentityFn<>()));
  
      PAssert.that(output).containsInAnyOrder(flattenLists(inputs));
      p.run();
    }
  
    @Test
    @Category(ValidatesRunner.class)
    public void testFlattenPCollectionsEmpty() {
      PCollection<String> output =
          PCollectionList.<String>empty(p)
              .apply(Flatten.pCollections())
              .setCoder(StringUtf8Coder.of());
  
      PAssert.that(output).empty();
      p.run();
    }
  
    @Test
    @Category(ValidatesRunner.class)
    public void testFlattenInputMultipleCopies() {
      int count = 5;
      PCollection<Long> longs = p.apply("mkLines", GenerateSequence.from(0).to(count));
      PCollection<Long> biggerLongs =
          p.apply("mkOtherLines", GenerateSequence.from(0).to(count))
              .apply(
                  MapElements.via(
                      new SimpleFunction<Long, Long>() {
                        @Override
                        public Long apply(Long input) {
                          return input + 10L;
                        }
                      }));
  
      PCollection<Long> flattened =
          PCollectionList.of(longs).and(longs).and(biggerLongs).apply(Flatten.pCollections());
  
      List<Long> expectedLongs = new ArrayList<>();
      for (int i = 0; i < count; i++) {
        // The duplicated input
        expectedLongs.add((long) i);
        expectedLongs.add((long) i);
        // The bigger longs
        expectedLongs.add(i + 10L);
      }
      PAssert.that(flattened).containsInAnyOrder(expectedLongs);
  
      p.run();
    }
  
    @Test
    @Category({ValidatesRunner.class, FlattenWithHeterogeneousCoders.class})
    public void testFlattenMultipleCoders() throws CannotProvideCoderException {
      PCollection<Long> bigEndianLongs =
          p.apply(
              "BigEndianLongs",
              Create.of(0L, 1L, 2L, 3L, null, 4L, 5L, null, 6L, 7L, 8L, null, 9L)
                  .withCoder(NullableCoder.of(BigEndianLongCoder.of())));
      PCollection<Long> varLongs =
          p.apply("VarLengthLongs", GenerateSequence.from(0).to(5)).setCoder(VarLongCoder.of());
  
      PCollection<Long> flattened =
          PCollectionList.of(bigEndianLongs)
              .and(varLongs)
              .apply(Flatten.pCollections())
              .setCoder(NullableCoder.of(VarLongCoder.of()));
      PAssert.that(flattened)
          .containsInAnyOrder(
              0L, 0L, 1L, 1L, 2L, 3L, 2L, 4L, 5L, 3L, 6L, 7L, 4L, 8L, 9L, null, null, null);
      p.run();
    }
  
    @Test
    @Category({ValidatesRunner.class, UsesSideInputs.class})
    public void testEmptyFlattenAsSideInput() {
      final PCollectionView<Iterable<String>> view =
          PCollectionList.<String>empty(p)
              .apply(Flatten.pCollections())
              .setCoder(StringUtf8Coder.of())
              .apply(View.asIterable());
  
      PCollection<String> output =
          p.apply(Create.of((Void) null).withCoder(VoidCoder.of()))
              .apply(
                  ParDo.of(
                          new DoFn<Void, String>() {
                            @ProcessElement
                            public void processElement(ProcessContext c) {
                              for (String side : c.sideInput(view)) {
                                c.output(side);
                              }
                            }
                          })
                      .withSideInputs(view));
  
      PAssert.that(output).empty();
      p.run();
    }
  
    @Test
    @Category(ValidatesRunner.class)
    public void testFlattenPCollectionsEmptyThenParDo() {
      PCollection<String> output =
          PCollectionList.<String>empty(p)
              .apply(Flatten.pCollections())
              .setCoder(StringUtf8Coder.of())
              .apply(ParDo.of(new IdentityFn<>()));
  
      PAssert.that(output).empty();
      p.run();
    }
  
    @Test
    @Category(NeedsRunner.class)
    public void testFlattenNoListsNoCoder() {
      // not ValidatesRunner because it should fail at pipeline construction time anyhow.
      thrown.expect(IllegalStateException.class);
      thrown.expectMessage("Unable to return a default Coder");
  
      PCollectionList.<ClassWithoutCoder>empty(p).apply(Flatten.pCollections());
  
      p.run();
    }
  
    /////////////////////////////////////////////////////////////////////////////
  
    @Test
    @Category(ValidatesRunner.class)
    public void testFlattenIterables() {
      PCollection<Iterable<String>> input =
          p.apply(
              Create.<Iterable<String>>of(LINES).withCoder(IterableCoder.of(StringUtf8Coder.of())));
  
      PCollection<String> output = input.apply(Flatten.iterables());
  
      PAssert.that(output).containsInAnyOrder(LINES_ARRAY);
  
      p.run();
    }
  
    @Test
    @Category(ValidatesRunner.class)
    public void testFlattenIterablesLists() {
      PCollection<List<String>> input =
          p.apply(Create.<List<String>>of(LINES).withCoder(ListCoder.of(StringUtf8Coder.of())));
  
      PCollection<String> output = input.apply(Flatten.iterables());
  
      PAssert.that(output).containsInAnyOrder(LINES_ARRAY);
  
      p.run();
    }
  
    @Test
    @Category(ValidatesRunner.class)
    public void testFlattenIterablesSets() {
      Set<String> linesSet = ImmutableSet.copyOf(LINES);
  
      PCollection<Set<String>> input =
          p.apply(Create.<Set<String>>of(linesSet).withCoder(SetCoder.of(StringUtf8Coder.of())));
  
      PCollection<String> output = input.apply(Flatten.iterables());
  
      PAssert.that(output).containsInAnyOrder(LINES_ARRAY);
  
      p.run();
    }
  
    @Test
    @Category(ValidatesRunner.class)
    public void testFlattenIterablesCollections() {
      Set<String> linesSet = ImmutableSet.copyOf(LINES);
  
      PCollection<Collection<String>> input =
          p.apply(
              Create.<Collection<String>>of(linesSet)
                  .withCoder(CollectionCoder.of(StringUtf8Coder.of())));
  
      PCollection<String> output = input.apply(Flatten.iterables());
  
      PAssert.that(output).containsInAnyOrder(LINES_ARRAY);
  
      p.run();
    }
  
    @Test
    @Category(ValidatesRunner.class)
    public void testFlattenIterablesEmpty() {
      PCollection<Iterable<String>> input =
          p.apply(
              Create.<Iterable<String>>of(NO_LINES)
                  .withCoder(IterableCoder.of(StringUtf8Coder.of())));
  
      PCollection<String> output = input.apply(Flatten.iterables());
  
      PAssert.that(output).containsInAnyOrder(NO_LINES_ARRAY);
  
      p.run();
    }
  
    @Test
    @Category(ValidatesRunner.class)
    public void testFlattenMultiplePCollectionsHavingMultipleConsumers() {
      PCollection<String> input = p.apply(Create.of("AA", "BBB", "CC"));
      final TupleTag<String> outputEvenLengthTag = new TupleTag<String>() {};
      final TupleTag<String> outputOddLengthTag = new TupleTag<String>() {};
  
      PCollectionTuple tuple =
          input.apply(
              ParDo.of(
                      new DoFn<String, String>() {
                        @ProcessElement
                        public void processElement(ProcessContext c) {
                          if (c.element().length() % 2 == 0) {
                            c.output(c.element());
                          } else {
                            c.output(outputOddLengthTag, c.element());
                          }
                        }
                      })
                  .withOutputTags(outputEvenLengthTag, TupleTagList.of(outputOddLengthTag)));
  
      PCollection<String> outputEvenLength = tuple.get(outputEvenLengthTag);
      PCollection<String> outputOddLength = tuple.get(outputOddLengthTag);
  
      PCollection<String> outputMerged =
          PCollectionList.of(outputEvenLength).and(outputOddLength).apply(Flatten.pCollections());
  
      PAssert.that(outputMerged).containsInAnyOrder("AA", "BBB", "CC");
      PAssert.that(outputEvenLength).containsInAnyOrder("AA", "CC");
      PAssert.that(outputOddLength).containsInAnyOrder("BBB");
  
      p.run();
    }
  
    @Test
    @Category(ValidatesRunner.class)
    public void testFlattenWithDifferentInputAndOutputCoders() {
      // This test exists to prevent a regression in Dataflow. It tests a
      // GroupByKey preceded by a Flatten with an SDK-specific input coder.
      PCollection<KV<String, String>> flattenInput =
          p.apply(Create.of(LINES))
              .apply(WithKeys.of("a"))
              .setCoder(SerializableCoder.of(new TypeDescriptor<KV<String, String>>() {}));
      PCollection<String> output =
          PCollectionList.of(flattenInput)
              .apply(Flatten.pCollections())
              .setCoder(KvCoder.of(StringUtf8Coder.of(), StringUtf8Coder.of()))
              .apply(GroupByKey.create())
              .apply(Values.create())
              .apply(
                  FlatMapElements.into(TypeDescriptors.strings())
                      .via((Iterable<String> values) -> values));
      PAssert.that(output).containsInAnyOrder(LINES);
      p.run();
    }
  
    @Test
    @Category(ValidatesRunner.class)
    public void testFlattenWithDifferentInputAndOutputCoders2() {
      // This test exists to prevent a regression in Dataflow. It tests a
      // GroupByKey followed by a Flatten with an SDK-specific output coder.
      PCollection<KV<String, Iterable<String>>> flattenInput =
          p.apply(Create.of(LINES))
              .apply(WithKeys.of("a"))
              .setCoder(KvCoder.of(StringUtf8Coder.of(), StringUtf8Coder.of()))
              .apply(GroupByKey.create());
      PCollection<String> output =
          PCollectionList.of(flattenInput)
              .apply(Flatten.pCollections())
              .setCoder(SerializableCoder.of(new TypeDescriptor<KV<String, Iterable<String>>>() {}))
              .apply(Values.create())
              .setCoder(IterableCoder.of(StringUtf8Coder.of()))
              .apply(
                  FlatMapElements.into(TypeDescriptors.strings())
                      .via((Iterable<String> values) -> values));
      PAssert.that(output).containsInAnyOrder(LINES);
      p.run();
    }
  
    /////////////////////////////////////////////////////////////////////////////
  
    @Test
    @Category(NeedsRunner.class)
    public void testFlattenWithPCollection() {
      PCollection<String> output =
          p.apply(Create.of(LINES))
              .apply("FlattenWithLines1", Flatten.with(p.apply("Create1", Create.of(LINES))))
              .apply("FlattenWithLines2", Flatten.with(p.apply("Create2", Create.of(LINES2))));
  
      PAssert.that(output).containsInAnyOrder(flattenLists(Arrays.asList(LINES, LINES2, LINES)));
      p.run();
    }
  
    @Test
    @Category(NeedsRunner.class)
    public void testFlattenWithPTransform() {
      PCollection<String> output =
          p.apply(Create.of(LINES))
              .apply("Create1", Flatten.with(Create.of(LINES)))
              .apply("Create2", Flatten.with(Create.of(LINES2)));
  
      PAssert.that(output).containsInAnyOrder(flattenLists(Arrays.asList(LINES, LINES2, LINES)));
      p.run();
    }
  
    /////////////////////////////////////////////////////////////////////////////
  
    @Test
    @Category(NeedsRunner.class)
    public void testEqualWindowFnPropagation() {
      PCollection<String> input1 =
          p.apply("CreateInput1", Create.of("Input1"))
              .apply("Window1", Window.into(FixedWindows.of(Duration.standardMinutes(1))));
      PCollection<String> input2 =
          p.apply("CreateInput2", Create.of("Input2"))
              .apply("Window2", Window.into(FixedWindows.of(Duration.standardMinutes(1))));
  
      PCollection<String> output =
          PCollectionList.of(input1).and(input2).apply(Flatten.pCollections());
  
      p.run();
  
      Assert.assertTrue(
          output
              .getWindowingStrategy()
              .getWindowFn()
              .isCompatible(FixedWindows.of(Duration.standardMinutes(1))));
    }
  
    @Test
    @Category(NeedsRunner.class)
    public void testCompatibleWindowFnPropagation() {
      PCollection<String> input1 =
          p.apply("CreateInput1", Create.of("Input1"))
              .apply("Window1", Window.into(Sessions.withGapDuration(Duration.standardMinutes(1))));
      PCollection<String> input2 =
          p.apply("CreateInput2", Create.of("Input2"))
              .apply("Window2", Window.into(Sessions.withGapDuration(Duration.standardMinutes(2))));
  
      PCollection<String> output =
          PCollectionList.of(input1).and(input2).apply(Flatten.pCollections());
  
      p.run();
  
      Assert.assertTrue(
          output
              .getWindowingStrategy()
              .getWindowFn()
              .isCompatible(Sessions.withGapDuration(Duration.standardMinutes(2))));
    }
  
    @Test
    public void testIncompatibleWindowFnPropagationFailure() {
      p.enableAbandonedNodeEnforcement(false);
  
      PCollection<String> input1 =
          p.apply("CreateInput1", Create.of("Input1"))
              .apply("Window1", Window.into(FixedWindows.of(Duration.standardMinutes(1))));
      PCollection<String> input2 =
          p.apply("CreateInput2", Create.of("Input2"))
              .apply("Window2", Window.into(FixedWindows.of(Duration.standardMinutes(2))));
  
      try {
        PCollectionList.of(input1).and(input2).apply(Flatten.pCollections());
        Assert.fail("Exception should have been thrown");
      } catch (IllegalStateException e) {
        Assert.assertTrue(
            e.getMessage().startsWith("Inputs to Flatten had incompatible window windowFns"));
      }
    }
  
    @Test
    public void testFlattenGetName() {
      Assert.assertEquals("Flatten.Iterables", Flatten.<String>iterables().getName());
      Assert.assertEquals("Flatten.PCollections", Flatten.<String>pCollections().getName());
      Assert.assertEquals("Flatten.With", Flatten.<String>with((PCollection<String>) null).getName());
    }
  
    /////////////////////////////////////////////////////////////////////////////
  
    private static class IdentityFn<T> extends DoFn<T, T> {
      @ProcessElement
      public void processElement(ProcessContext c) {
        c.output(c.element());
      }
    }
  
    private PCollectionList<String> makePCollectionListOfStrings(
        Pipeline p, List<List<String>> lists) {
      return makePCollectionList(p, StringUtf8Coder.of(), lists);
    }
  
    private <T> PCollectionList<T> makePCollectionList(
        Pipeline p, Coder<T> coder, List<List<T>> lists) {
      List<PCollection<T>> pcs = new ArrayList<>();
      int index = 0;
      for (List<T> list : lists) {
        PCollection<T> pc = p.apply("Create" + index++, Create.of(list).withCoder(coder));
        pcs.add(pc);
      }
      return PCollectionList.of(pcs);
    }
  
    private <T> List<T> flattenLists(List<List<T>> lists) {
      List<T> flattened = new ArrayList<>();
      for (List<T> list : lists) {
        flattened.addAll(list);
      }
      return flattened;
    }
  }
  