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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,
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   * See the License for the specific language governing permissions and
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  package org.apache.beam.runners.samza.translation;
  
  import org.apache.beam.runners.core.Concatenate;
  import org.apache.beam.sdk.runners.AppliedPTransform;
  import org.apache.beam.sdk.transforms.Combine;
  import org.apache.beam.sdk.transforms.PTransform;
  import org.apache.beam.sdk.transforms.View;
  import org.apache.beam.sdk.util.construction.SingleInputOutputOverrideFactory;
  import org.apache.beam.sdk.values.PCollection;
  import org.apache.beam.sdk.values.PCollectionView;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.collect.Iterables;
  
  /** Samza override for {@link View} (side input) transforms. */
  class SamzaPublishViewTransformOverride<ElemT, ViewT>
      extends SingleInputOutputOverrideFactory<
          PCollection<ElemT>, PCollection<ElemT>, View.CreatePCollectionView<ElemT, ViewT>> {
    @Override
    public PTransformReplacement<PCollection<ElemT>, PCollection<ElemT>> getReplacementTransform(
        AppliedPTransform<
                PCollection<ElemT>, PCollection<ElemT>, View.CreatePCollectionView<ElemT, ViewT>>
            transform) {
  
      @SuppressWarnings("unchecked")
      PCollection<ElemT> input =
          (PCollection<ElemT>) Iterables.getOnlyElement(transform.getInputs().values());
  
      return PTransformReplacement.of(
          input, new SamzaCreatePCollectionViewTransform<>(transform.getTransform().getView()));
    }
  
    private static class SamzaCreatePCollectionViewTransform<ElemT, ViewT>
        extends PTransform<PCollection<ElemT>, PCollection<ElemT>> {
      private final PCollectionView<ViewT> view;
  
      public SamzaCreatePCollectionViewTransform(PCollectionView<ViewT> view) {
        this.view = view;
      }
  
      @Override
      public PCollection<ElemT> expand(PCollection<ElemT> input) {
        // This actually creates a branch in the graph that publishes the view but then returns
        // the original input. This is copied from the Flink runner.
        input
            .apply(Combine.globally(new Concatenate<ElemT>()).withoutDefaults())
            .apply(new SamzaPublishView<>(view));
        return input;
      }
    }
  }
  