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.flink.translation.functions;
  
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.HashMap;
  import java.util.HashSet;
  import java.util.Iterator;
  import java.util.List;
  import java.util.Map;
  import java.util.Set;
  import org.apache.beam.runners.core.SideInputReader;
  import org.apache.beam.sdk.options.PipelineOptions;
  import org.apache.beam.sdk.transforms.windowing.BoundedWindow;
  import org.apache.beam.sdk.transforms.windowing.PaneInfo;
  import org.apache.beam.sdk.transforms.windowing.TimestampCombiner;
  import org.apache.beam.sdk.transforms.windowing.WindowFn;
  import org.apache.beam.sdk.values.KV;
  import org.apache.beam.sdk.values.WindowedValue;
  import org.apache.beam.sdk.values.WindowedValues;
  import org.apache.beam.sdk.values.WindowingStrategy;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.collect.Iterables;
  import org.apache.flink.api.java.tuple.Tuple2;
  import org.apache.flink.util.Collector;
  import org.joda.time.Instant;
  
  /**
   * A Flink combine runner that builds a map of merged windows and produces output after seeing all
   * input. This is similar to what{@link org.apache.beam.runners.core.ReduceFnRunner} does.
   */
  public class HashingFlinkCombineRunner<K, InputT, AccumT, OutputT, W extends BoundedWindow>
      extends AbstractFlinkCombineRunner<K, InputT, AccumT, OutputT, W> {
  
    @Override
    public void combine(
        FlinkCombiner<K, InputT, AccumT, OutputT> flinkCombiner,
        WindowingStrategy<Object, W> windowingStrategy,
        SideInputReader sideInputReader,
        PipelineOptions options,
        Iterable<WindowedValue<KV<K, InputT>>> elements,
        Collector<WindowedValue<KV<K, OutputT>>> out)
        throws Exception {
  
      @SuppressWarnings("unchecked")
      TimestampCombiner timestampCombiner = windowingStrategy.getTimestampCombiner();
  
      // Flink Iterable can be iterated over only once.
      List<WindowedValue<KV<K, InputT>>> inputs = new ArrayList<>();
      Iterables.addAll(inputs, elements);
  
      Set<W> windows = collectWindows(inputs);
      Map<W, W> windowToMergeResult = mergeWindows(windowingStrategy, windows);
  
      // Combine all windowedValues into map
      Map<W, Tuple2<AccumT, Instant>> mapState = new HashMap<>();
      Iterator<WindowedValue<KV<K, InputT>>> iterator = inputs.iterator();
      WindowedValue<KV<K, InputT>> currentValue = iterator.next();
      K key = currentValue.getValue().getKey();
      do {
        for (BoundedWindow w : currentValue.getWindows()) {
          @SuppressWarnings("unchecked")
          W currentWindow = (W) w;
          W mergedWindow = windowToMergeResult.get(currentWindow);
          mergedWindow = mergedWindow == null ? currentWindow : mergedWindow;
          Set<W> singletonW = Collections.singleton(mergedWindow);
          Tuple2<AccumT, Instant> accumAndInstant = mapState.get(mergedWindow);
          if (accumAndInstant == null) {
            AccumT accumT =
                flinkCombiner.firstInput(
                    key, currentValue.getValue().getValue(), options, sideInputReader, singletonW);
            Instant windowTimestamp =
                timestampCombiner.assign(mergedWindow, currentValue.getTimestamp());
            accumAndInstant = new Tuple2<>(accumT, windowTimestamp);
            mapState.put(mergedWindow, accumAndInstant);
          } else {
            accumAndInstant.f0 =
                flinkCombiner.addInput(
                    key,
                    accumAndInstant.f0,
                    currentValue.getValue().getValue(),
                    options,
                    sideInputReader,
                    singletonW);
            accumAndInstant.f1 =
                timestampCombiner.combine(
                    accumAndInstant.f1,
                    timestampCombiner.assign(mergedWindow, currentValue.getTimestamp()));
          }
        }
        if (iterator.hasNext()) {
          currentValue = iterator.next();
        } else {
          break;
        }
      } while (true);
  
      // Output the final value of combiners
      for (Map.Entry<W, Tuple2<AccumT, Instant>> entry : mapState.entrySet()) {
        AccumT accumulator = entry.getValue().f0;
        Instant windowTimestamp = entry.getValue().f1;
        out.collect(
            WindowedValues.of(
                KV.of(
                    key,
                    flinkCombiner.extractOutput(
                        key,
                        accumulator,
                        options,
                        sideInputReader,
                        Collections.singleton(entry.getKey()))),
                windowTimestamp,
                entry.getKey(),
                PaneInfo.NO_FIRING));
      }
    }
  
    private Map<W, W> mergeWindows(WindowingStrategy<Object, W> windowingStrategy, Set<W> windows)
        throws Exception {
      WindowFn<Object, W> windowFn = windowingStrategy.getWindowFn();
  
      if (!windowingStrategy.needsMerge()) {
        // Return an empty map, indicating that every window is not merged.
        return Collections.emptyMap();
      }
  
      Map<W, W> windowToMergeResult = new HashMap<>();
      windowFn.mergeWindows(new MergeContextImpl(windowFn, windows, windowToMergeResult));
      return windowToMergeResult;
    }
  
    private class MergeContextImpl extends WindowFn<Object, W>.MergeContext {
  
      private Set<W> windows;
      private Map<W, W> windowToMergeResult;
  
      MergeContextImpl(WindowFn<Object, W> windowFn, Set<W> windows, Map<W, W> windowToMergeResult) {
        windowFn.super();
        this.windows = windows;
        this.windowToMergeResult = windowToMergeResult;
      }
  
      @Override
      public Collection<W> windows() {
        return windows;
      }
  
      @Override
      public void merge(Collection<W> toBeMerged, W mergeResult) throws Exception {
        for (W w : toBeMerged) {
          windowToMergeResult.put(w, mergeResult);
        }
      }
    }
  
    private Set<W> collectWindows(Iterable<WindowedValue<KV<K, InputT>>> values) {
      Set<W> windows = new HashSet<>();
      for (WindowedValue<?> value : values) {
        for (BoundedWindow untypedWindow : value.getWindows()) {
          @SuppressWarnings("unchecked")
          W window = (W) untypedWindow;
          windows.add(window);
        }
      }
      return windows;
    }
  }
  