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.*;
  import io.activej.dataflow.node.Node;
  import io.activej.dataflow.node.Nodes;
  import org.jetbrains.annotations.Nullable;
  
  import java.util.ArrayList;
  import java.util.List;
  
  @ExposedInternals
  public final class Empty<T> extends Dataset<T> {
  	public final @Nullable List<Partition> partitions;
  
  	public Empty(StreamSchema<T> streamSchema, @Nullable List<Partition> partitions) {
  		super(streamSchema);
  		this.partitions = partitions;
  	}
  
  	@Override
  	public List<StreamId> channels(DataflowContext context) {
  		DataflowGraph graph = context.getGraph();
  		List<StreamId> outputStreamIds = new ArrayList<>();
  		List<Partition> partitions = this.partitions == null ? graph.getAvailablePartitions() : this.partitions;
  		int index = context.generateNodeIndex();
  		for (Partition partition : partitions) {
  			Node node = Nodes.emptySupplier(index);
  			graph.addNode(partition, node);
  			outputStreamIds.addAll(node.getOutputs());
  		}
  		return outputStreamIds;
  	}
  }
  