/*
 * Copyright (C) 2009-2010 Institute for Computational Biomedicine,
 *                    Weill Medical College of Cornell University
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

package edu.cornell.med.icb.goby.stats;

import gominer.Fisher;
import it.unimi.dsi.fastutil.objects.ObjectArraySet;

/**
 * Calculates Fisher exact test P-value for an observed count difference between comparison
 * groups (requires exactly two groups).
 *
 * @author Fabien Campagne
 *         Date: Jan 11, 2010
 *         Time: 7:06:31 PM
 */
public class FisherExactTestCalculator extends StatisticCalculator {
    public FisherExactTestCalculator(final DifferentialExpressionResults results) {
        this();
        setResults(results);
    }

    public FisherExactTestCalculator() {
        super();
    }

    @Override
    public boolean canDo(final String[] group) {
        return group.length == 2;
    }

    @Override
    public DifferentialExpressionInfo evaluate(final DifferentialExpressionCalculator differentialExpressionCalculator,
                                               final NormalizationMethod method,
                                               final DifferentialExpressionResults results,
                                               final DifferentialExpressionInfo info,
                                               final String... group) {

        final String groupA = group[0];
        final String groupB = group[1];

        final int fisherPValuesStatIndex = defineStatisticId(results, "fisher-exact-test", method, group);

        final ObjectArraySet<String> samplesA = differentialExpressionCalculator.getSamples(groupA);
        final ObjectArraySet<String> samplesB = differentialExpressionCalculator.getSamples(groupB);

        int sumCountInA = 0; // = new double[samplesA.size()];
        int sumCountInB = 0; // = new double[samplesB.size()];

        for (final String sample : samplesA) {
            sumCountInA += differentialExpressionCalculator.getOverlapCount(sample, info.getElementId());
        }

        for (final String sample : samplesB) {
            sumCountInB += differentialExpressionCalculator.getOverlapCount(sample, info.getElementId());
        }

        int totalCountInA = 0;
        int totalCountInB = 0;

        for (final String sample : samplesA) {
            totalCountInA += differentialExpressionCalculator.getSumOverlapCounts(sample);

        }
        for (final String sample : samplesB) {
            totalCountInB += differentialExpressionCalculator.getSumOverlapCounts(sample);

        }


        /**
         * Calculates the 2-tailed gominer.Fisher p value, using the counts that are
         * expected to be readily available in the system
         *
         * @param totalChanged The number of genes changed in the experiment
         * N1
         * @param changedInNode The number of genes changed in a particular node
         * x
         * @param total The total number of genes in the experiment (changed and
         * unchanged)     N1+N2
         * @param inNode The number of genes in the node (changed and unchanged)
         * x+y
         * @return 2-tailed gominer.Fisher p value
         */
        // public double fisher(final int totalChanged, final int changedInNode, final int total, final int inNode) {
        final Fisher fisher = new Fisher();
        final double pValue = fisher.fisher(totalCountInA, sumCountInA, totalCountInA + totalCountInB, sumCountInA + sumCountInB);


        /* Test : fisher.fisher(40,10,100,30)=
                     Fisher's Exact Test
        http://www.langsrud.com/fisher.htm
        ------------------------------------------
         TABLE = [ 10 , 20 , 30 , 40 ]
        Left   : p-value = 0.2533310713617698
        Right  : p-value = 0.8676419647894328
        2-Tail : p-value = 0.5044757698516504
        ------------------------------------------
        */
        info.statistics.size(results.getNumberOfStatistics());
        info.statistics.set(fisherPValuesStatIndex, pValue);

        return info;
    }


}
