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.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.Node;
  import io.activej.dataflow.node.Nodes;
  
  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;
  
  @ExposedInternals
  public final class UnionAll<T> extends Dataset<T> {
  	public final Dataset<T> left;
  	public final Dataset<T> right;
  
  	public UnionAll(Dataset<T> left, Dataset<T> right) {
  		super(left.streamSchema());
  		this.left = left;
  		this.right = right;
  	}
  
  	@Override
  	public List<StreamId> channels(DataflowContext context) {
  		DataflowGraph graph = context.getGraph();
  		List<StreamId> outputStreamIds = new ArrayList<>();
  
  		List<StreamId> leftStreamIds = left.channels(context);
  		List<StreamId> rightStreamIds = right.channels(context);
  
  		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();
  			assert !streamIds.isEmpty();
  
  			if (streamIds.size() == 1) {
  				outputStreamIds.add(streamIds.get(0));
  				continue;
  			}
  
  			Node nodeUnion = Nodes.union(index, streamIds);
  			graph.addNode(entry.getKey(), nodeUnion);
  
  			outputStreamIds.addAll(nodeUnion.getOutputs());
  		}
  
  		return outputStreamIds;
  	}
  
  	@Override
  	public Collection<Dataset<?>> getBases() {
  		return List.of(left, right);
  	}
  }
  