/*
    * 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.ooc.command;
  
  import com.google.common.base.Preconditions;
  import org.apache.giraph.bsp.BspService;
  import org.apache.giraph.comm.messages.MessageStore;
  import org.apache.giraph.ooc.OutOfCoreEngine;
  import org.apache.giraph.ooc.data.DiskBackedEdgeStore;
  import org.apache.giraph.ooc.data.DiskBackedMessageStore;
  import org.apache.giraph.ooc.data.DiskBackedPartitionStore;
  
  import java.io.IOException;
  
  /**
   * IOCommand to load partition data, edge data (if in INPUT_SUPERSTEP), and
   * message data (if in compute supersteps). Also, this command can be used to
   * prefetch a partition to be processed in the next superstep.
   */
  public class LoadPartitionIOCommand extends IOCommand {
    /**
     * Which superstep this partition should be loaded for? (can be current
     * superstep or next superstep -- in case of prefetching).
     */
    private final long superstep;
  
    /**
     * Constructor
     *
     * @param oocEngine out-of-core engine
     * @param partitionId id of the partition to be loaded
     * @param superstep superstep to load the partition for
     */
    public LoadPartitionIOCommand(OutOfCoreEngine oocEngine, int partitionId,
                                  long superstep) {
      super(oocEngine, partitionId);
      this.superstep = superstep;
    }
  
    @Override
    public boolean execute() throws IOException {
      boolean executed = false;
      if (oocEngine.getMetaPartitionManager()
          .startLoadingPartition(partitionId, superstep)) {
        long currentSuperstep = oocEngine.getSuperstep();
        DiskBackedPartitionStore partitionStore =
            (DiskBackedPartitionStore)
                oocEngine.getServerData().getPartitionStore();
        numBytesTransferred +=
            partitionStore.loadPartitionData(partitionId);
        if (currentSuperstep == BspService.INPUT_SUPERSTEP &&
            superstep == currentSuperstep) {
          DiskBackedEdgeStore edgeStore =
              (DiskBackedEdgeStore) oocEngine.getServerData().getEdgeStore();
          numBytesTransferred +=
              edgeStore.loadPartitionData(partitionId);
        }
        MessageStore messageStore;
        if (currentSuperstep == superstep) {
          messageStore = oocEngine.getServerData().getCurrentMessageStore();
        } else {
          Preconditions.checkState(superstep == currentSuperstep + 1);
          messageStore = oocEngine.getServerData().getIncomingMessageStore();
        }
        if (messageStore != null) {
          numBytesTransferred += ((DiskBackedMessageStore) messageStore)
              .loadPartitionData(partitionId);
        }
        oocEngine.getMetaPartitionManager()
            .doneLoadingPartition(partitionId, superstep);
        executed = true;
      }
      return executed;
    }
  
    @Override
    public IOCommandType getType() {
      return IOCommandType.LOAD_PARTITION;
    }
  
    @Override
    public String toString() {
      return "LoadPartitionIOCommand: (partitionId = " + partitionId + ", " +
         "superstep = " + superstep + ")";
   }
 }