/*
 * 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.giraph.graph.partition;

import java.util.List;
import java.util.Map;
import java.util.Set;

import org.apache.giraph.graph.WorkerInfo;

/**
 * Describes what is required to send and wait for in a potential partition
 * exchange between workers.
 */
public class PartitionExchange {
    /** Workers that I am dependent on before I can continue */
    private final Set<WorkerInfo> myDependencyWorkerSet;
    /** Workers that I need to sent partitions to */
    private final Map<WorkerInfo, List<Integer>> sendWorkerPartitionMap;

    /**
     * Only constructor.
     *
     * @param myDependencyWorkerSet All the workers I must wait for
     * @param sendWorkerPartitionMap Partitions I need to send to other workers
     */
    public PartitionExchange(
            Set<WorkerInfo> myDependencyWorkerSet,
            Map<WorkerInfo, List<Integer>> sendWorkerPartitionMap) {
        this.myDependencyWorkerSet = myDependencyWorkerSet;
        this.sendWorkerPartitionMap = sendWorkerPartitionMap;
    }

    /**
     * Get the workers that I must wait for
     *
     * @return Set of workers I must wait for
     */
    public Set<WorkerInfo> getMyDependencyWorkerSet() {
        return myDependencyWorkerSet;
    }

    /**
     * Get a mapping of worker to list of partition ids I need to send to.
     *
     * @return Mapping of worker to partition id list I will send to.
     */
    public Map<WorkerInfo, List<Integer>> getSendWorkerPartitionMap() {
        return sendWorkerPartitionMap;
    }

    /**
     * Is this worker involved in a partition exchange?  Receiving or sending?
     *
     * @return True if needs to be involved in the exchange, false otherwise.
     */
    public boolean doExchange() {
        return !myDependencyWorkerSet.isEmpty() ||
               !sendWorkerPartitionMap.isEmpty();
    }
}
