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.StreamId;
  import io.activej.dataflow.graph.StreamSchema;
  import io.activej.dataflow.node.Node;
  import io.activej.dataflow.node.Nodes;
  import io.activej.datastream.processor.join.LeftJoiner;
  
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.List;
  import java.util.concurrent.ThreadLocalRandom;
  import java.util.function.Function;
  
  import static io.activej.dataflow.dataset.DatasetUtils.repartitionAndSort;
  
  @ExposedInternals
  public final class Join<K, L, R, V> extends SortedDataset<K, V> {
  	public final SortedDataset<K, L> left;
  	public final SortedDataset<K, R> right;
  	public final LeftJoiner<K, L, R, V> leftJoiner;
  
  	public final int sharderNonce = ThreadLocalRandom.current().nextInt();
  
  	public Join(
  		SortedDataset<K, L> left, SortedDataset<K, R> right, LeftJoiner<K, L, R, V> leftJoiner,
  		StreamSchema<V> resultStreamSchema, Function<V, K> keyFunction
  	) {
  		super(resultStreamSchema, left.keyComparator(), left.keyType(), keyFunction);
  		this.left = left;
  		this.right = right;
  		this.leftJoiner = leftJoiner;
  	}
  
  	@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));
  
  		assert leftStreamIds.size() == rightStreamIds.size();
  		int index = context.generateNodeIndex();
  		for (int i = 0; i < leftStreamIds.size(); i++) {
  			StreamId leftStreamId = leftStreamIds.get(i);
  			StreamId rightStreamId = rightStreamIds.get(i);
  			Node node = Nodes.join(index, leftStreamId, rightStreamId, left.keyComparator(),
  				left.keyFunction(), right.keyFunction(), leftJoiner);
  			graph.addNode(graph.getPartition(leftStreamId), node);
  			outputStreamIds.addAll(node.getOutputs());
  		}
  		return outputStreamIds;
  	}
  
  	@Override
  	public Collection<Dataset<?>> getBases() {
  		return List.of(left, right);
  	}
  }
  