/*
    * 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 com.google.common.collect.MapMaker;
  import com.google.common.collect.Maps;
  
  import java.io.DataInput;
  import java.io.DataOutput;
  import java.io.IOException;
  import java.util.Collections;
  import java.util.Map;
  import java.util.concurrent.ConcurrentMap;
  
  import org.apache.giraph.conf.ImmutableClassesGiraphConfiguration;
  import org.apache.giraph.factories.MessageValueFactory;
  import org.apache.hadoop.io.Writable;
  import org.apache.hadoop.io.WritableComparable;
  
  /**
   * Abstract class for {@link MessageStore} which allows any kind
   * of object to hold messages for one vertex.
   * Simple in memory message store implemented with a two level concurrent
   * hash map.
   *
   * @param <I> Vertex id
   * @param <M> Message data
   * @param <T> Type of object which holds messages for one vertex
   */
  public abstract class SimpleMessageStore<I extends WritableComparable,
      M extends Writable, T> implements MessageStore<I, M>  {
    /** Message class */
    protected final MessageValueFactory<M> messageValueFactory;
    /** Partition split info */
    protected final PartitionSplitInfo<I> partitionInfo;
    /** Map from partition id to map from vertex id to messages for that vertex */
    protected final ConcurrentMap<Integer, ConcurrentMap<I, T>> map;
    /** Giraph configuration */
    protected final ImmutableClassesGiraphConfiguration<I, ?, ?> config;
  
    /**
     * Constructor
     *
     * @param messageValueFactory Message class held in the store
     * @param partitionInfo Partition split info
     * @param config Giraph configuration
     */
    public SimpleMessageStore(
        MessageValueFactory<M> messageValueFactory,
        PartitionSplitInfo<I> partitionInfo,
        ImmutableClassesGiraphConfiguration<I, ?, ?> config) {
      this.messageValueFactory = messageValueFactory;
      this.partitionInfo = partitionInfo;
      this.config = config;
      map = new MapMaker().concurrencyLevel(
          config.getNettyServerExecutionConcurrency()).makeMap();
    }
  
    /**
     * Get messages as an iterable from message storage
     *
     * @param messages Message storage
     * @return Messages as an iterable
     */
    protected abstract Iterable<M> getMessagesAsIterable(T messages);
  
    /**
     * Get number of messages in partition map
     *
     * @param partitionMap Partition map in which to count messages
     * @return Number of messages in partition map
     */
    protected abstract int getNumberOfMessagesIn(
        ConcurrentMap<I, T> partitionMap);
  
    /**
     * Write message storage to {@link DataOutput}
     *
     * @param messages Message storage
     * @param out Data output
     * @throws IOException
     */
    protected abstract void writeMessages(T messages, DataOutput out) throws
       IOException;
 
   /**
    * Read message storage from {@link DataInput}
    *
    * @param in Data input
    * @return Message storage
    * @throws IOException
    */
   protected abstract T readFieldsForMessages(DataInput in) throws IOException;
 
   /**
    * Get id of partition which holds vertex with selected id
    *
    * @param vertexId Id of vertex
    * @return Id of partiton
    */
   protected int getPartitionId(I vertexId) {
     return partitionInfo.getPartitionId(vertexId);
   }
 
   /**
    * If there is already a map of messages related to the partition id
    * return that map, otherwise create a new one, put it in global map and
    * return it.
    *
    * @param partitionId Id of partition
    * @return Message map for this partition
    */
   protected ConcurrentMap<I, T> getOrCreatePartitionMap(int partitionId) {
     ConcurrentMap<I, T> partitionMap = map.get(partitionId);
     if (partitionMap == null) {
       ConcurrentMap<I, T> tmpMap = new MapMaker().concurrencyLevel(
           config.getNettyServerExecutionConcurrency()).makeMap();
       partitionMap = map.putIfAbsent(partitionId, tmpMap);
       if (partitionMap == null) {
         partitionMap = tmpMap;
       }
     }
     return partitionMap;
   }
 
   @Override
   public void finalizeStore() {
   }
 
   @Override
   public Iterable<I> getPartitionDestinationVertices(int partitionId) {
     ConcurrentMap<I, ?> partitionMap = map.get(partitionId);
     return (partitionMap == null) ? Collections.<I>emptyList() :
         partitionMap.keySet();
   }
 
   @Override
   public boolean hasMessagesForVertex(I vertexId) {
     ConcurrentMap<I, ?> partitionMap =
         map.get(getPartitionId(vertexId));
     return partitionMap != null && partitionMap.containsKey(vertexId);
   }
 
   @Override
   public Iterable<M> getVertexMessages(I vertexId) {
     ConcurrentMap<I, T> partitionMap = map.get(getPartitionId(vertexId));
     if (partitionMap == null) {
       return Collections.<M>emptyList();
     }
     T messages = partitionMap.get(vertexId);
     return (messages == null) ? Collections.<M>emptyList() :
         getMessagesAsIterable(messages);
   }
 
   @Override
   public void writePartition(DataOutput out,
       int partitionId) throws IOException {
     ConcurrentMap<I, T> partitionMap = map.get(partitionId);
     out.writeBoolean(partitionMap != null);
     if (partitionMap != null) {
       out.writeInt(partitionMap.size());
       for (Map.Entry<I, T> entry : partitionMap.entrySet()) {
         entry.getKey().write(out);
         writeMessages(entry.getValue(), out);
       }
     }
   }
 
   @Override
   public void readFieldsForPartition(DataInput in,
       int partitionId) throws IOException {
     if (in.readBoolean()) {
       ConcurrentMap<I, T> partitionMap = Maps.newConcurrentMap();
       int numVertices = in.readInt();
       for (int v = 0; v < numVertices; v++) {
         I vertexId = config.createVertexId();
         vertexId.readFields(in);
         partitionMap.put(vertexId, readFieldsForMessages(in));
       }
       map.put(partitionId, partitionMap);
     }
   }
 
   @Override
   public void clearVertexMessages(I vertexId) {
     ConcurrentMap<I, ?> partitionMap =
         map.get(getPartitionId(vertexId));
     if (partitionMap != null) {
       partitionMap.remove(vertexId);
     }
   }
 
   @Override
   public void clearPartition(int partitionId) {
     map.remove(partitionId);
   }
 
   @Override
   public boolean hasMessagesForPartition(int partitionId) {
     ConcurrentMap<I, T> partitionMessages = map.get(partitionId);
     return partitionMessages != null && !partitionMessages.isEmpty();
   }
 
   @Override
   public void clearAll() {
     map.clear();
   }
 }