content: /*
   * Copyright (C) 2020 ActiveJ LLC.
   *
   * Licensed 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 io.activej.dataflow.dataset.impl;
  
  import io.activej.common.annotation.ExposedInternals;
  import io.activej.dataflow.dataset.Dataset;
  import io.activej.dataflow.dataset.SortedDataset;
  import io.activej.dataflow.graph.DataflowContext;
  import io.activej.dataflow.graph.DataflowGraph;
  import io.activej.dataflow.graph.Partition;
  import io.activej.dataflow.graph.StreamId;
  import io.activej.dataflow.node.impl.Merge;
  
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.List;
  import java.util.Map;
  import java.util.stream.Collectors;
  import java.util.stream.Stream;
  
  import static io.activej.dataflow.dataset.DatasetUtils.repartitionAndSort;
  
  @ExposedInternals
  public final class Union<K, T> extends SortedDataset<K, T> {
  	public final SortedDataset<K, T> left;
  	public final SortedDataset<K, T> right;
  
  	public final int sharderNonce;
  
  	public Union(SortedDataset<K, T> left, SortedDataset<K, T> right, int nonce) {
  		super(left.streamSchema(), left.keyComparator(), left.keyType(), left.keyFunction());
  		this.left = left;
  		this.right = right;
  		this.sharderNonce = nonce;
  	}
  
  	@Override
  	public List<StreamId> channels(DataflowContext context) {
  		DataflowGraph graph = context.getGraph();
  		List<StreamId> outputStreamIds = new ArrayList<>();
  
  		DataflowContext next = context.withFixedNonce(sharderNonce);
  
  		List<StreamId> leftStreamIds = left.channels(next);
  		List<StreamId> rightStreamIds = repartitionAndSort(next, right, graph.getPartitions(leftStreamIds));
  
  		Map<Partition, List<StreamId>> partitioned = Stream.concat(leftStreamIds.stream(), rightStreamIds.stream())
  			.collect(Collectors.groupingBy(graph::getPartition));
  
  		int index = context.generateNodeIndex();
  
  		for (Map.Entry<Partition, List<StreamId>> entry : partitioned.entrySet()) {
  			List<StreamId> streamIds = entry.getValue();
  
  			Merge<K, T>.Builder nodeMergeBuilder = Merge.builder(index, keyFunction(), keyComparator(), true);
  			for (StreamId streamId : streamIds) {
  				nodeMergeBuilder.withInput(streamId);
  			}
  			Merge<K, T> nodeMerge = nodeMergeBuilder.build();
  			graph.addNode(entry.getKey(), nodeMerge);
  
  			outputStreamIds.add(nodeMerge.output);
  		}
  
  		return outputStreamIds;
  	}
  
  	@Override
  	public Collection<Dataset<?>> getBases() {
  		return List.of(left, right);
  	}
  }
  