/*

  * 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.utils;

 import org.apache.hadoop.io.Writable;

 import org.apache.hadoop.io.WritableComparable;

 import java.io.IOException;

 /**

  * VertexIdData iterator for

  * {@link ByteArrayOneMessageToManyIds}

  *

  * @param <I> vertexId type

  * @param <M> message type

  */

 public class OneMessageToManyIdsIterator<I extends WritableComparable,

     M extends Writable> implements VertexIdMessageIterator<I, M> {

   /** VertexIdMessages object to iterate over */

   private final ByteArrayOneMessageToManyIds<I, M> vertexIdMessages;

   /** Reader of the serialized edges */

   private final ExtendedDataInput extendedDataInput;

   /** Current vertex Id*/

   private I vertexId;

   /** Current message */

   private M msg;

   /** Counts of ids left to read before next message */

   private int idsToRead = 0;

   /** Size of message read */

   private int msgSize = 0;

   /** Is current message newly read */

   private boolean newMessage;

   /**

    * Constructor

    *

    * @param vertexIdMessages vertexId messages object to iterate over

    */

   public OneMessageToManyIdsIterator(

       final ByteArrayOneMessageToManyIds<I, M> vertexIdMessages) {

     this.vertexIdMessages = vertexIdMessages;

     this.extendedDataInput = vertexIdMessages.getConf()

         .createExtendedDataInput(vertexIdMessages.extendedDataOutput);

   }

   @Override

   public I getCurrentVertexId() {

     return vertexId;

   }

   @Override

   public M getCurrentMessage() {

     return getCurrentData();

   }

   @Override

   public M getCurrentData() {

     return msg;

   }

   @Override

   public M releaseCurrentData() {

     M releasedData = msg;

     msg = null;

     return releasedData;

   }

   @Override

   public I releaseCurrentVertexId() {

     I releasedVertexId = vertexId;

     vertexId = null;

     return releasedVertexId;

   }

   @Override

   public boolean hasNext() {

     return extendedDataInput.available() > 0;

   }

   /**

    * Properly initialize vertexId & msg object before calling next()

    */

   private void initialize() {

     if (vertexId == null) {

       vertexId = vertexIdMessages.getConf().createVertexId();

     }

     if (msg == null) {

       msg = vertexIdMessages.createData();

     }

   }

   @Override

   public void next() {

     initialize();

     try {

       if (idsToRead == 0) {

         newMessage = true; // a new message is read

         int initial = extendedDataInput.getPos();

         msg.readFields(extendedDataInput);

         msgSize = extendedDataInput.getPos() - initial;

         idsToRead = extendedDataInput.readInt();

       } else {

         newMessage = false; // same as previous message

       }

       vertexId.readFields(extendedDataInput);

       idsToRead -= 1;

     } catch (IOException e) {

       throw new IllegalStateException("next: IOException", e);

     }

   }

   @Override

   public int getCurrentMessageSize() {

     return getCurrentDataSize();

   }

   @Override

   public int getCurrentDataSize() {

     return msgSize;

   }

   @Override

   public boolean isNewMessage() {

     return newMessage;

   }

 }