/*

  * 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.comm.messages;

 import java.util.Collections;

 import java.util.List;

 import java.util.concurrent.ConcurrentMap;

 import org.apache.giraph.conf.ImmutableClassesGiraphConfiguration;

 import org.apache.giraph.factories.MessageValueFactory;

 import org.apache.giraph.utils.VertexIdIterator;

 import org.apache.giraph.utils.WritableUtils;

 import org.apache.hadoop.io.Writable;

 import org.apache.hadoop.io.WritableComparable;

 /**

  * Abstract Implementation of {@link SimpleMessageStore} where

  * multiple messages are stored per vertex as a list

  * Used when there is no combiner provided.

  *

  * @param <I> Vertex id

  * @param <M> Message data

  * @param <L> List type

  */

 public abstract class AbstractListPerVertexStore<I extends WritableComparable,

   M extends Writable, L extends List> extends SimpleMessageStore<I, M, L> {

   /**

    * Constructor

    *

    * @param messageValueFactory Message class held in the store

    * @param partitionInfo Partition split info

    * @param config Hadoop configuration

    */

   public AbstractListPerVertexStore(

     MessageValueFactory<M> messageValueFactory,

     PartitionSplitInfo<I> partitionInfo,

     ImmutableClassesGiraphConfiguration<I, ?, ?> config) {

     super(messageValueFactory, partitionInfo, config);

   }

   /**

    * Create an instance of L

    * @return instance of L

    */

   protected abstract L createList();

   /**

    * Get the list of pointers for a vertex

    * Each pointer has information of how to access an encoded message

    * for this vertex

    *

    * @param iterator vertex id iterator

    * @return pointer list

    */

   protected L getOrCreateList(VertexIdIterator<I> iterator) {

     int partitionId = getPartitionId(iterator.getCurrentVertexId());

     ConcurrentMap<I, L> partitionMap = getOrCreatePartitionMap(partitionId);

     L list = partitionMap.get(iterator.getCurrentVertexId());

     if (list == null) {

       L newList = createList();

       list = partitionMap.putIfAbsent(

         iterator.releaseCurrentVertexId(), newList);

       if (list == null) {

         list = newList;

       }

     }

     return list;

   }

   /**

    * Get the list of pointers for a vertex

    * Each pointer has information of how to access an encoded message

    * for this vertex

    * This method will take ownership of the vertex id from the

    * iterator if necessary (when used in the partition map entry)

    *

    * @param vertexId vertex id

    * @return pointer list

    */

   protected L getOrCreateList(I vertexId) {

     int partitionId = getPartitionId(vertexId);

     ConcurrentMap<I, L> partitionMap = getOrCreatePartitionMap(partitionId);

     L list = partitionMap.get(vertexId);

     if (list == null) {

       L newList = createList();

       I copyId = WritableUtils.createCopy(vertexId);

       list = partitionMap.putIfAbsent(copyId, newList);

       if (list == null) {

         list = newList;

       }

     }

     return list;

   }

   @Override

   public Iterable<M> getVertexMessages(I vertexId) {

     ConcurrentMap<I, L> partitionMap =

         map.get(getPartitionId(vertexId));

     if (partitionMap == null) {

       return Collections.<M>emptyList();

     }

     L list = partitionMap.get(vertexId);

     return list == null ? Collections.<M>emptyList() :

         getMessagesAsIterable(list);

   }

 }