/*

  * 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.reducers.impl;

 import java.io.DataInput;

 import java.io.DataOutput;

 import java.io.IOException;

 import org.apache.giraph.reducers.ReduceOperation;

 import org.apache.giraph.writable.kryo.KryoWritableWrapper;

 /**

  * Reduce operation which wraps reduced value in KryoWritableWrapper,

  * so we don't need to worry about it being writable

  *

  * @param <S> Single value type

  * @param <R> Reduced value type

  */

 public abstract class KryoWrappedReduceOperation<S, R>

     implements ReduceOperation<S, KryoWritableWrapper<R>> {

   /**

    * Look at ReduceOperation.reduce.

    *

    * @param reduceInto Partial value into which to reduce and store the result

    * @param valueToReduce Single value to be reduced

    */

   public abstract void reduce(R reduceInto, S valueToReduce);

   /**

    * Look at ReduceOperation.reduceMerge.

    *

    * @param reduceInto Partial value into which to reduce and store the result

    * @param valueToReduce Partial value to be reduced

    */

   public abstract void reduceMerge(R reduceInto, R valueToReduce);

   /**

    * Look at ReduceOperation.createValue.

    *

    * @return Neutral value

    */

   public abstract R createValue();

   @Override

   public final KryoWritableWrapper<R> createInitialValue() {

     return new KryoWritableWrapper<>(createValue());

   }

   @Override

   public final KryoWritableWrapper<R> reduce(

       KryoWritableWrapper<R> wrapper, S value) {

     reduce(wrapper.get(), value);

     return wrapper;

   }

   @Override

   public final KryoWritableWrapper<R> reduceMerge(

       KryoWritableWrapper<R> wrapper,

       KryoWritableWrapper<R> wrapperToReduce) {

     reduceMerge(wrapper.get(), wrapperToReduce.get());

     return wrapper;

   }

   @Override

   public void write(DataOutput dataOutput) throws IOException {

   }

   @Override

   public void readFields(DataInput dataInput) throws IOException {

   }

 }