/**
 * Copyright (c) 2011, The University of Southampton and the individual contributors.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 *   *  Redistributions of source code must retain the above copyright notice,
 *      this list of conditions and the following disclaimer.
 *
 *   *  Redistributions in binary form must reproduce the above copyright notice,
 *      this list of conditions and the following disclaimer in the documentation
 *      and/or other materials provided with the distribution.
 *
 *   *  Neither the name of the University of Southampton nor the names of its
 *      contributors may be used to endorse or promote products derived from this
 *      software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package org.openimaj.ml.clustering.assignment.hard;

import org.openimaj.citation.annotation.Reference;
import org.openimaj.citation.annotation.ReferenceType;
import org.openimaj.ml.clustering.assignment.HardAssigner;
import org.openimaj.util.pair.IntFloatPair;

/**
 * An assigner that wraps another hard assigner and only produces valid
 * assignments if the closest cluster is within (or outside) of a given
 * threshold distance.
 * <p>
 * Invalid assignments are marked by a cluster id of -1, and (if applicable)
 * distance of {@link Float#NaN}. Users of this class must check the assignments
 * and filter as necessary.
 * 
 * @author Jonathon Hare (jsh2@ecs.soton.ac.uk)
 * @param <DATATYPE>
 *            the primitive array datatype which represents a centroid of this
 *            cluster.
 */
@Reference(
                author = { "Y. Cai", "W. Tong", "L. Yang", "A. G. Hauptmann" },
                title = "Constrained Keypoint Quantization: Towards Better Bag-of-Words Model for Large-scale Multimedia Retrieval",
                type = ReferenceType.Inproceedings,
                year = "2012",
                booktitle = "ACM International Conference on Multimedia Retrieval",
                customData = { "location", "Hong Kong, China" })
public class ConstrainedFloatAssigner<DATATYPE> implements HardAssigner<DATATYPE, float[], IntFloatPair> {
        HardAssigner<DATATYPE, float[], IntFloatPair> internalAssigner;

        boolean allowIfGreater = false;
        float threshold;

        /**
         * Construct the ConstrainedFloatAssigner with the given assigner and
         * threshold. Assignments will be rejected if the distance given by the
         * internal assigner are greater than the threshold.
         * 
         * @param internalAssigner
         *            the internal assigner for computing distances.
         * @param threshold
         *            the threshold at which assignments are rejected.
         */
        public ConstrainedFloatAssigner(HardAssigner<DATATYPE, float[], IntFloatPair> internalAssigner, float threshold) {
                this.threshold = threshold;
        }

        /**
         * Construct the ConstrainedFloatAssigner with the given assigner and
         * threshold. The greater flag determines if assignments should be rejected
         * if the distance generated by the internal assigner is greater than the
         * threshold (false) or less than the threshold (true).
         * 
         * @param internalAssigner
         *            the internal assigner for computing distances.
         * @param threshold
         *            the threshold at which assignments are rejected.
         * @param greater
         *            if true distances less than the threshold are rejected; if
         *            false then distances greater than the threshold are rejected.
         */
        public ConstrainedFloatAssigner(HardAssigner<DATATYPE, float[], IntFloatPair> internalAssigner, float threshold,
                        boolean greater)
        {
                this.allowIfGreater = greater;
                this.threshold = threshold;
        }

        private boolean allow(float distance) {
                if (allowIfGreater) {
                        return distance > threshold;
                }

                return distance < threshold;
        }

        @Override
        public int[] assign(DATATYPE[] data) {
                final int[] indices = new int[data.length];
                final float[] distances = new float[data.length];

                assignDistance(data, indices, distances);

                return indices;
        }

        @Override
        public int assign(DATATYPE data) {
                return assignDistance(data).first;
        }

        @Override
        public void assignDistance(DATATYPE[] data, int[] indices, float[] distances) {
                internalAssigner.assignDistance(data, indices, distances);

                for (int i = 0; i < data.length; i++) {
                        if (!allow(distances[i])) {
                                distances[i] = Float.NaN;
                                indices[i] = -1;
                        }
                }
        }

        @Override
        public IntFloatPair assignDistance(DATATYPE data) {
                final IntFloatPair res = internalAssigner.assignDistance(data);

                if (!allow(res.second)) {
                        res.second = Float.NaN;
                        res.first = -1;
                }

                return res;
        }

        @Override
        public int size() {
                return this.internalAssigner.size();
        }

        @Override
        public int numDimensions() {
                return this.internalAssigner.numDimensions();
        }
}