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.
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  package org.apache.beam.runners.dataflow.worker;
  
  import org.apache.beam.runners.core.KeyedWorkItem;
  import org.apache.beam.runners.core.StateInternalsFactory;
  import org.apache.beam.runners.core.SystemReduceFn;
  import org.apache.beam.sdk.coders.Coder;
  import org.apache.beam.sdk.transforms.windowing.BoundedWindow;
  import org.apache.beam.sdk.util.AppliedCombineFn;
  import org.apache.beam.sdk.values.KV;
  import org.apache.beam.sdk.values.WindowingStrategy;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.base.Preconditions;
  
  /** {@link GroupAlsoByWindowFn}'s that merge windows and groups elements in those windows. */
  public abstract class StreamingGroupAlsoByWindowsDoFns {
    public static <K, InputT, AccumT, OutputT, W extends BoundedWindow>
        GroupAlsoByWindowFn<KeyedWorkItem<K, InputT>, KV<K, OutputT>> create(
            final WindowingStrategy<?, W> windowingStrategy,
            StateInternalsFactory<K> stateInternalsFactory,
            final AppliedCombineFn<K, InputT, AccumT, OutputT> combineFn,
            final Coder<K> keyCoder) {
      Preconditions.checkNotNull(combineFn);
      return StreamingGroupAlsoByWindowViaWindowSetFn.create(
          windowingStrategy, stateInternalsFactory, SystemReduceFn.combining(keyCoder, combineFn));
    }
  
    public static <K, V, W extends BoundedWindow>
        GroupAlsoByWindowFn<KeyedWorkItem<K, V>, KV<K, Iterable<V>>> createForIterable(
            final WindowingStrategy<?, W> windowingStrategy,
            StateInternalsFactory<K> stateInternalsFactory,
            Coder<V> inputCoder) {
      // If the windowing strategy indicates we're doing a reshuffle, use the special-path.
      if (StreamingGroupAlsoByWindowReshuffleFn.isReshuffle(windowingStrategy)) {
        return new StreamingGroupAlsoByWindowReshuffleFn<>();
      } else {
        return StreamingGroupAlsoByWindowViaWindowSetFn.create(
            windowingStrategy, stateInternalsFactory, SystemReduceFn.buffering(inputCoder));
      }
    }
  }
  