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.dataflow.worker;
  
  import com.google.api.services.dataflow.model.SideInputInfo;
  import java.util.HashSet;
  import java.util.Set;
  import org.apache.beam.runners.core.SideInputReader;
  import org.apache.beam.sdk.transforms.windowing.BoundedWindow;
  import org.apache.beam.sdk.values.PCollectionView;
  import org.apache.beam.sdk.values.TupleTag;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.base.Supplier;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.base.Suppliers;
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  /**
   * A {@link SideInputReader} which initializes on first {@link #get(PCollectionView, BoundedWindow)}
   * call.
   */
  public class LazilyInitializedSideInputReader implements SideInputReader {
    private final Set<TupleTag<?>> tupleTags;
    private final Supplier<SideInputReader> lazyInitSideInputReader;
  
    public LazilyInitializedSideInputReader(
        Iterable<? extends SideInputInfo> sideInputInfos, Supplier<SideInputReader> sideInputReader) {
      tupleTags = new HashSet<>();
      for (SideInputInfo sideInputInfo : sideInputInfos) {
        tupleTags.add(new TupleTag<>(sideInputInfo.getTag()));
      }
      lazyInitSideInputReader = Suppliers.memoize(sideInputReader);
    }
  
    @Override
    public <T> @Nullable T get(PCollectionView<T> view, BoundedWindow window) {
      return lazyInitSideInputReader.get().get(view, window);
    }
  
    @Override
    public <T> boolean contains(PCollectionView<T> view) {
      return tupleTags.contains(view.getTagInternal());
    }
  
    @Override
    public boolean isEmpty() {
      return tupleTags.isEmpty();
    }
  }
  