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.core;
  
  import java.io.Serializable;
  import java.util.Collection;
  import org.apache.beam.sdk.options.PipelineOptions;
  import org.apache.beam.sdk.transforms.CombineFnBase.GlobalCombineFn;
  import org.apache.beam.sdk.transforms.windowing.BoundedWindow;
  
  /**
   * An interface that runs a {@link GlobalCombineFn} with unified APIs.
   *
   * <p>Different combine functions have their own implementations. For example, the implementation
   * can skip allocating {@code Combine.Context}, if the combine function doesn't use it.
   */
  public interface GlobalCombineFnRunner<InputT, AccumT, OutputT> extends Serializable {
    /**
     * Forwards the call to a {@link GlobalCombineFn} to create the accumulator.
     *
     * <p>It constructs a {@code CombineWithContext.Context} from {@link PipelineOptions} and {@link
     * SideInputReader} if it is required.
     */
    AccumT createAccumulator(
        PipelineOptions options,
        SideInputReader sideInputReader,
        Collection<? extends BoundedWindow> windows);
  
    /**
     * Forwards the call to a {@link GlobalCombineFn} to add the input.
     *
     * <p>It constructs a {@code CombineWithContext.Context} from {@link PipelineOptions} and {@link
     * SideInputReader} if it is required.
     */
    AccumT addInput(
        AccumT accumulator,
        InputT value,
        PipelineOptions options,
        SideInputReader sideInputReader,
        Collection<? extends BoundedWindow> windows);
  
    /**
     * Forwards the call to a {@link GlobalCombineFn} to merge accumulators.
     *
     * <p>It constructs a {@code CombineWithContext.Context} from {@link PipelineOptions} and {@link
     * SideInputReader} if it is required.
     */
    AccumT mergeAccumulators(
        Iterable<AccumT> accumulators,
        PipelineOptions options,
        SideInputReader sideInputReader,
        Collection<? extends BoundedWindow> windows);
  
    /**
     * Forwards the call to a {@link GlobalCombineFn} to extract the output.
     *
     * <p>It constructs a {@code CombineWithContext.Context} from {@link PipelineOptions} and {@link
     * SideInputReader} if it is required.
     */
    OutputT extractOutput(
        AccumT accumulator,
        PipelineOptions options,
        SideInputReader sideInputReader,
        Collection<? extends BoundedWindow> windows);
  
    /**
     * Forwards the call to a {@link GlobalCombineFn} to compact the accumulator.
     *
     * <p>It constructs a {@code CombineWithContext.Context} from {@link PipelineOptions} and {@link
     * SideInputReader} if it is required.
     */
    AccumT compact(
        AccumT accumulator,
        PipelineOptions options,
        SideInputReader sideInputReader,
        Collection<? extends BoundedWindow> windows);
  }
  