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.testing;
  
  import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
  import java.io.Serializable;
  import java.util.Collection;
  import org.apache.beam.sdk.coders.Coder;
  import org.apache.beam.sdk.coders.CoderException;
  import org.apache.beam.sdk.transforms.windowing.BoundedWindow;
  import org.apache.beam.sdk.util.CoderUtils;
  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.collect.ImmutableList;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.collect.ImmutableSet;
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  /**
   * A {@link Supplier} that returns a static set of {@link BoundedWindow BoundedWindows}. The
   * supplier is {@link Serializable}, and handles encoding and decoding the windows with a {@link
   * Coder} provided for the windows.
   */
  // Spotbugs thinks synchronization is for the fields, but it is for the act of decoding
  @SuppressFBWarnings("IS2_INCONSISTENT_SYNC")
  @SuppressWarnings({
    "nullness" // TODO(https://github.com/apache/beam/issues/20497)
  })
  final class WindowSupplier implements Supplier<Collection<BoundedWindow>>, Serializable {
    private final Coder<? extends BoundedWindow> coder;
    private final Collection<byte[]> encodedWindows;
  
    /** Access via {@link #get()}. */
    private transient @Nullable Collection<BoundedWindow> windows;
  
    public static <W extends BoundedWindow> WindowSupplier of(Coder<W> coder, Iterable<W> windows) {
      ImmutableSet.Builder<byte[]> windowsBuilder = ImmutableSet.builder();
      for (W window : windows) {
        try {
          windowsBuilder.add(CoderUtils.encodeToByteArray(coder, window));
        } catch (CoderException e) {
          throw new IllegalArgumentException(
              "Could not encode provided windows with the provided window coder", e);
        }
      }
      return new WindowSupplier(coder, windowsBuilder.build());
    }
  
    private WindowSupplier(Coder<? extends BoundedWindow> coder, Collection<byte[]> encodedWindows) {
      this.coder = coder;
      this.encodedWindows = encodedWindows;
    }
  
    @Override
    public Collection<BoundedWindow> get() {
      if (windows == null) {
        decodeWindows();
      }
      return windows;
    }
  
    private synchronized void decodeWindows() {
      if (windows == null) {
        ImmutableList.Builder<BoundedWindow> windowsBuilder = ImmutableList.builder();
        for (byte[] encoded : encodedWindows) {
          try {
            windowsBuilder.add(CoderUtils.decodeFromByteArray(coder, encoded));
          } catch (CoderException e) {
            throw new IllegalArgumentException(
                "Could not decode provided windows with the provided window coder", e);
          }
        }
        this.windows = windowsBuilder.build();
      }
    }
  }
  