/*
    * 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.block_app.reducers.collect;
  
  import java.io.DataInput;
  import java.io.DataOutput;
  import java.io.IOException;
  
  import org.apache.giraph.reducers.impl.KryoWrappedReduceOperation;
  import org.apache.giraph.types.ops.PrimitiveTypeOps;
  import org.apache.giraph.types.ops.TypeOpsUtils;
  import org.apache.giraph.types.ops.collections.ResettableIterator;
  import org.apache.giraph.types.ops.collections.array.WArrayList;
  import org.apache.giraph.utils.WritableUtils;
  
  /**
   * Collect primitive values reduce operation
   *
   * @param <S> Primitive Writable type, which has its type ops
   */
  public class CollectPrimitiveReduceOperation<S>
      extends KryoWrappedReduceOperation<S, WArrayList<S>> {
    /**
     * Type ops if available, or null
     */
    private PrimitiveTypeOps<S> typeOps;
  
    /** For reflection only */
    public CollectPrimitiveReduceOperation() {
    }
  
    public CollectPrimitiveReduceOperation(PrimitiveTypeOps<S> typeOps) {
      this.typeOps = typeOps;
    }
  
    @Override
    public WArrayList<S> createValue() {
      return createList();
    }
  
    @Override
    public void reduce(WArrayList<S> reduceInto, S value) {
      reduceInto.addW(value);
    }
  
    @Override
    public void reduceMerge(final WArrayList<S> reduceInto,
        WArrayList<S> toReduce) {
      ResettableIterator<S> iterator = toReduce.fastIteratorW();
      while (iterator.hasNext()) {
        reduceInto.addW(iterator.next());
      }
    }
  
    public WArrayList<S> createList() {
      return typeOps.createArrayList();
    }
  
    @Override
    public void write(DataOutput out) throws IOException {
      WritableUtils.writeClass(typeOps.getTypeClass(), out);
    }
  
    @Override
    public void readFields(DataInput in) throws IOException {
      typeOps = TypeOpsUtils.getPrimitiveTypeOps(
          WritableUtils.<S>readClass(in));
    }
  }