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.spark.structuredstreaming.translation.batch;
  
  import java.io.IOException;
  import org.apache.beam.runners.spark.structuredstreaming.translation.TransformTranslator;
  import org.apache.beam.runners.spark.structuredstreaming.translation.utils.ScalaInterop.Fun1;
  import org.apache.beam.sdk.transforms.Combine;
  import org.apache.beam.sdk.transforms.Combine.CombineFn;
  import org.apache.beam.sdk.transforms.CombineWithContext;
  import org.apache.beam.sdk.values.KV;
  import org.apache.beam.sdk.values.PCollection;
  import org.apache.beam.sdk.values.WindowedValue;
  import org.apache.spark.sql.Dataset;
  import org.apache.spark.sql.Encoder;
  import org.apache.spark.sql.expressions.Aggregator;
  
  /**
   * Translator for {@link Combine.GroupedValues} if the {@link CombineFn} doesn't require context /
   * side-inputs.
   *
   * <p>This doesn't require a Spark {@link Aggregator}. Instead it can directly use the respective
   * {@link CombineFn} to reduce each iterable of values into an aggregated output value.
   */
  class CombineGroupedValuesTranslatorBatch<K, InT, AccT, OutT>
      extends TransformTranslator<
          PCollection<? extends KV<K, ? extends Iterable<InT>>>,
          PCollection<KV<K, OutT>>,
          Combine.GroupedValues<K, InT, OutT>> {
  
    CombineGroupedValuesTranslatorBatch() {
      super(0.2f);
    }
  
    @Override
    protected void translate(Combine.GroupedValues<K, InT, OutT> transform, Context cxt)
        throws IOException {
      CombineFn<InT, AccT, OutT> combineFn = (CombineFn<InT, AccT, OutT>) transform.getFn();
  
      Encoder<WindowedValue<KV<K, OutT>>> enc = cxt.windowedEncoder(cxt.getOutput().getCoder());
      Dataset<WindowedValue<KV<K, Iterable<InT>>>> inputDs = (Dataset) cxt.getDataset(cxt.getInput());
  
      cxt.putDataset(cxt.getOutput(), inputDs.map(reduce(combineFn), enc));
    }
  
    @Override
    public boolean canTranslate(Combine.GroupedValues<K, InT, OutT> transform) {
      return !(transform.getFn() instanceof CombineWithContext);
    }
  
    private static <K, InT, AccT, OutT>
        Fun1<WindowedValue<KV<K, Iterable<InT>>>, WindowedValue<KV<K, OutT>>> reduce(
            CombineFn<InT, AccT, OutT> fn) {
      return wv -> {
        KV<K, ? extends Iterable<InT>> kv = wv.getValue();
        AccT acc = null;
        for (InT in : kv.getValue()) {
          acc = fn.addInput(acc != null ? acc : fn.createAccumulator(), in);
        }
        OutT res = acc != null ? fn.extractOutput(acc) : fn.defaultValue();
        return wv.withValue(KV.of(kv.getKey(), res));
      };
    }
  }
  