001/**
002 * Copyright (c) 2011, The University of Southampton and the individual contributors.
003 * All rights reserved.
004 *
005 * Redistribution and use in source and binary forms, with or without modification,
006 * are permitted provided that the following conditions are met:
007 *
008 *   *  Redistributions of source code must retain the above copyright notice,
009 *      this list of conditions and the following disclaimer.
010 *
011 *   *  Redistributions in binary form must reproduce the above copyright notice,
012 *      this list of conditions and the following disclaimer in the documentation
013 *      and/or other materials provided with the distribution.
014 *
015 *   *  Neither the name of the University of Southampton nor the names of its
016 *      contributors may be used to endorse or promote products derived from this
017 *      software without specific prior written permission.
018 *
019 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
020 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
021 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
022 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
023 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
024 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
025 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
026 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
027 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
028 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
029 */
030package org.openimaj.util.function.context;
031
032import java.util.ArrayList;
033import java.util.List;
034
035import org.openimaj.util.data.Context;
036import org.openimaj.util.function.Function;
037
038/**
039 * Transform a {@link List} of {@link Context} instances to a {@link List} of IN
040 * and immediately hand this list to an internal function. Return this
041 * function's application on the klist as stream
042 * 
043 * @author Sina Samangooei (ss@ecs.soton.ac.uk)
044 * 
045 * @param <IN>
046 * @param <OUT>
047 */
048public class ContextListTransformFunction<IN, OUT> implements Function<List<Context>, OUT> {
049        private ContextExtractor<IN> extractor;
050        private Function<List<IN>, OUT> inner;
051
052        /**
053         * @param extract
054         *            the extraction strategy
055         * @param inner
056         *            the function applied to the transformed list
057         */
058        public ContextListTransformFunction(ContextExtractor<IN> extract, Function<List<IN>, OUT> inner)
059        {
060                this.extractor = extract;
061                this.inner = inner;
062        }
063
064        /**
065         * @param key
066         *            the key to extract (a {@link KeyContextExtractor} is used)
067         * @param inner
068         *            function applied to the transformed list
069         */
070        public ContextListTransformFunction(String key, Function<List<IN>, OUT> inner) {
071                this.extractor = new KeyContextExtractor<IN>(key);
072                this.inner = inner;
073        }
074
075        @Override
076        public OUT apply(List<Context> in) {
077                final List<IN> ret = new ArrayList<IN>();
078                for (final Context context : in) {
079                        ret.add(this.extractor.extract(context));
080                }
081                return inner.apply(ret);
082        }
083}