001/*
002 * Copyright (c) 2007-2016 Concurrent, Inc. All Rights Reserved.
003 *
004 * Project and contact information: http://www.cascading.org/
005 *
006 * This file is part of the Cascading project.
007 *
008 * Licensed under the Apache License, Version 2.0 (the "License");
009 * you may not use this file except in compliance with the License.
010 * You may obtain a copy of the License at
011 *
012 *     http://www.apache.org/licenses/LICENSE-2.0
013 *
014 * Unless required by applicable law or agreed to in writing, software
015 * distributed under the License is distributed on an "AS IS" BASIS,
016 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
017 * See the License for the specific language governing permissions and
018 * limitations under the License.
019 */
020
021package cascading.flow.stream.duct;
022
023import java.util.Iterator;
024
025/**
026 *
027 */
028public class OpenReducingDuct<Incoming, Outgoing> extends Duct<Grouping<Incoming, Iterator<Incoming>>, Outgoing> implements OpenWindow
029  {
030  final Reducing reducing;
031
032  public OpenReducingDuct( Duct<Outgoing, ?> next )
033    {
034    super( next );
035
036    reducing = (Reducing) getNext();
037    }
038
039  @Override
040  public void receive( Duct previous, Grouping<Incoming, Iterator<Incoming>> grouping )
041    {
042    // don't start a grouping if there are no values in the group
043    if( !grouping.joinIterator.hasNext() )
044      return;
045
046    reducing.startGroup( previous, grouping.key );
047
048    while( grouping.joinIterator.hasNext() )
049      next.receive( this, (Outgoing) grouping.joinIterator.next() );
050
051    reducing.completeGroup( previous, grouping.key );
052    }
053  }