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 java.util.Collection;
  import java.util.Collections;
  import org.apache.beam.sdk.runners.AppliedPTransform;
  import org.apache.beam.sdk.transforms.Impulse;
  import org.apache.beam.sdk.transforms.PTransform;
  import org.apache.beam.sdk.transforms.windowing.BoundedWindow;
  import org.apache.beam.sdk.values.PBegin;
  import org.apache.beam.sdk.values.PCollection;
  import org.apache.beam.sdk.values.WindowedValue;
  import org.apache.beam.sdk.values.WindowedValues;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.annotations.VisibleForTesting;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.collect.Iterables;
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  /** The evaluator for the {@link Impulse} transform. Produces only empty byte arrays. */
  class ImpulseEvaluatorFactory implements TransformEvaluatorFactory {
    private final EvaluationContext ctxt;
  
    ImpulseEvaluatorFactory(EvaluationContext ctxt) {
      this.ctxt = ctxt;
    }
  
    @Nullable
    @Override
    public <InputT> TransformEvaluator<InputT> forApplication(
        AppliedPTransform<?, ?, ?> application, CommittedBundle<?> inputBundle) {
      return (TransformEvaluator<InputT>) new ImpulseEvaluator(ctxt, (AppliedPTransform) application);
    }
  
    @Override
    public void cleanup() {
      // Impulse has no state, so do nothing.
    }
  
    private static class ImpulseEvaluator implements TransformEvaluator<ImpulseShard> {
      private final EvaluationContext ctxt;
      private final AppliedPTransform<?, PCollection<byte[]>, Impulse> transform;
      private final StepTransformResult.Builder<ImpulseShard> result;
  
      private ImpulseEvaluator(
          EvaluationContext ctxt, AppliedPTransform<?, PCollection<byte[]>, Impulse> transform) {
        this.ctxt = ctxt;
        this.transform = transform;
        this.result = StepTransformResult.withoutHold(transform);
      }
  
      @Override
      public void processElement(WindowedValue<ImpulseShard> element) throws Exception {
        PCollection<byte[]> outputPCollection =
            (PCollection<byte[]>) Iterables.getOnlyElement(transform.getOutputs().values());
        result.addOutput(
            ctxt.createBundle(outputPCollection)
                .add(WindowedValues.valueInGlobalWindow(new byte[0])));
      }
  
      @Override
      public TransformResult<ImpulseShard> finishBundle() throws Exception {
        return result.build();
      }
    }
  
    /**
     * The {@link RootInputProvider} for the {@link Impulse} {@link PTransform}. Produces a single
     * {@link ImpulseShard}.
     */
    static class ImpulseRootProvider implements RootInputProvider<byte[], ImpulseShard, PBegin> {
      private final EvaluationContext ctxt;
  
      ImpulseRootProvider(EvaluationContext ctxt) {
        this.ctxt = ctxt;
      }
  
      @Override
      public Collection<CommittedBundle<ImpulseShard>> getInitialInputs(
          AppliedPTransform<PBegin, PCollection<byte[]>, PTransform<PBegin, PCollection<byte[]>>>
              transform,
          int targetParallelism) {
        return Collections.singleton(
            ctxt.<ImpulseShard>createRootBundle()
                .add(WindowedValues.valueInGlobalWindow(new ImpulseShard()))
                .commit(BoundedWindow.TIMESTAMP_MIN_VALUE));
      }
    }
  
    @VisibleForTesting
    static class ImpulseShard {}
  }
  