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.runners.direct;
  
  import static org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.base.Preconditions.checkState;
  
  import java.util.HashSet;
  import java.util.Map;
  import java.util.Set;
  import org.apache.beam.runners.core.SplittableParDoViaKeyedWorkItems;
  import org.apache.beam.runners.direct.DirectGroupByKey.DirectGroupAlsoByWindow;
  import org.apache.beam.runners.direct.DirectGroupByKey.DirectGroupByKeyOnly;
  import org.apache.beam.sdk.Pipeline.PipelineVisitor;
  import org.apache.beam.sdk.runners.TransformHierarchy;
  import org.apache.beam.sdk.transforms.GroupByKey;
  import org.apache.beam.sdk.transforms.PTransform;
  import org.apache.beam.sdk.transforms.ParDo;
  import org.apache.beam.sdk.values.PCollection;
  import org.apache.beam.sdk.values.PValue;
  import org.apache.beam.sdk.values.TupleTag;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.collect.ImmutableSet;
  
  /**
   * A pipeline visitor that tracks all keyed {@link PValue PValues}. A {@link PValue} is keyed if it
   * is the result of a {@link PTransform} that produces keyed outputs. A {@link PTransform} that
   * produces keyed outputs is assumed to colocate output elements that share a key.
   *
   * <p>All {@link GroupByKey} transforms, or their runner-specific implementation primitive, produce
   * keyed output.
   */
  // TODO: Handle Key-preserving transforms when appropriate and more aggressively make PTransforms
  // unkeyed
  @SuppressWarnings({
    "rawtypes", // TODO(https://github.com/apache/beam/issues/20447)
    "nullness" // TODO(https://github.com/apache/beam/issues/20497)
  })
  class KeyedPValueTrackingVisitor extends PipelineVisitor.Defaults {
  
    private static final Set<Class<? extends PTransform>> PRODUCES_KEYED_OUTPUTS =
        ImmutableSet.of(
            SplittableParDoViaKeyedWorkItems.GBKIntoKeyedWorkItems.class,
            DirectGroupByKeyOnly.class,
            DirectGroupAlsoByWindow.class);
  
    private final Set<PValue> keyedValues;
    private boolean finalized;
  
    public static KeyedPValueTrackingVisitor create() {
      return new KeyedPValueTrackingVisitor();
    }
  
    private KeyedPValueTrackingVisitor() {
      this.keyedValues = new HashSet<>();
    }
  
    @Override
    public CompositeBehavior enterCompositeTransform(TransformHierarchy.Node node) {
      checkState(
          !finalized,
          "Attempted to use a %s that has already been finalized on a pipeline (visiting node %s)",
          KeyedPValueTrackingVisitor.class.getSimpleName(),
          node);
      return CompositeBehavior.ENTER_TRANSFORM;
    }
  
    @Override
    public void leaveCompositeTransform(TransformHierarchy.Node node) {
      checkState(
          !finalized,
          "Attempted to use a %s that has already been finalized on a pipeline (visiting node %s)",
          KeyedPValueTrackingVisitor.class.getSimpleName(),
          node);
      if (node.isRootNode()) {
        finalized = true;
      } else if (PRODUCES_KEYED_OUTPUTS.contains(node.getTransform().getClass())) {
        Map<TupleTag<?>, PCollection<?>> outputs = node.getOutputs();
        for (PValue output : outputs.values()) {
          keyedValues.add(output);
        }
      }
    }
  
    @Override
    public void visitValue(PValue value, TransformHierarchy.Node producer) {
      boolean inputsAreKeyed = true;
      for (PValue input : producer.getInputs().values()) {
        inputsAreKeyed = inputsAreKeyed && keyedValues.contains(input);
      }
      if (PRODUCES_KEYED_OUTPUTS.contains(producer.getTransform().getClass())
          || (isKeyPreserving(producer.getTransform()) && inputsAreKeyed)) {
        keyedValues.add(value);
      }
    }
  
    public Set<PValue> getKeyedPValues() {
      checkState(
          finalized, "can't call getKeyedPValues before a Pipeline has been completely traversed");
      return keyedValues;
    }
  
    private static boolean isKeyPreserving(PTransform<?, ?> transform) {
      // This is a hacky check for what is considered key-preserving to the direct runner.
      // The most obvious alternative would be a package-private marker interface, but
      // better to make this obviously hacky so it is less likely to proliferate. Meanwhile
      // we intend to allow explicit expression of key-preserving DoFn in the model.
      if (transform instanceof ParDo.MultiOutput) {
        ParDo.MultiOutput<?, ?> parDo = (ParDo.MultiOutput<?, ?>) transform;
        return parDo.getFn() instanceof ParDoMultiOverrideFactory.ToKeyedWorkItem;
      } else {
        return false;
      }
    }
  }
  