/* ======================================================
 * JFreeChart : a chart library for the Java(tm) platform
 * ======================================================
 *
 * (C) Copyright 2000-present, by David Gilbert and Contributors.
 *
 * Project Info:  https://www.jfree.org/jfreechart/index.html
 *
 * This library is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation; either version 2.1 of the License, or
 * (at your option) any later version.
 *
 * This library 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 Lesser General Public
 * License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301,
 * USA.
 *
 * [Oracle and Java are registered trademarks of Oracle and/or its affiliates. 
 * Other names may be trademarks of their respective owners.]
 *
 * ----------------------------
 * BoxAndWhiskerCalculator.java
 * ----------------------------
 * (C) Copyright 2003-present, by David Gilbert and Contributors.
 *
 * Original Author:  David Gilbert;
 * Contributor(s):   -;
 *
 */

package org.jfree.data.statistics;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import org.jfree.chart.util.Args;

/**
 * A utility class that calculates the mean, median, quartiles Q1 and Q3, plus
 * a list of outlier values...all from an arbitrary list of
 * {@code Number} objects.
 */
public abstract class BoxAndWhiskerCalculator {

    private BoxAndWhiskerCalculator() {
        // no requirement to instantiate
    }

    /**
     * Calculates the statistics required for a {@link BoxAndWhiskerItem}
     * from a list of {@code Number} objects.  Any items in the list
     * that are {@code null}, not an instance of {@code Number}, or
     * equivalent to {@code Double.NaN}, will be ignored.
     *
     * @param values  a list of numbers (a {@code null} list is not
     *                permitted).
     *
     * @return A box-and-whisker item.
     */
    public static BoxAndWhiskerItem calculateBoxAndWhiskerStatistics(
                                        List values) {
        return calculateBoxAndWhiskerStatistics(values, true);
    }

    /**
     * Calculates the statistics required for a {@link BoxAndWhiskerItem}
     * from a list of {@code Number} objects.  Any items in the list
     * that are {@code null}, not an instance of {@code Number}, or
     * equivalent to {@code Double.NaN}, will be ignored.
     *
     * @param values  a list of numbers (a {@code null} list is not
     *                permitted).
     * @param stripNullAndNaNItems  a flag that controls the handling of null
     *     and NaN items.
     *
     * @return A box-and-whisker item.
     */
    public static BoxAndWhiskerItem calculateBoxAndWhiskerStatistics(
            List values, boolean stripNullAndNaNItems) {

        Args.nullNotPermitted(values, "values");

        List vlist;
        if (stripNullAndNaNItems) {
            vlist = new ArrayList(values.size());
            Iterator iterator = values.listIterator();
            while (iterator.hasNext()) {
                Object obj = iterator.next();
                if (obj instanceof Number) {
                    Number n = (Number) obj;
                    double v = n.doubleValue();
                    if (!Double.isNaN(v)) {
                        vlist.add(n);
                    }
                }
            }
        }
        else {
            vlist = values;
        }
        Collections.sort(vlist);

        double mean = Statistics.calculateMean(vlist, false);
        double median = Statistics.calculateMedian(vlist, false);
        double q1 = calculateQ1(vlist);
        double q3 = calculateQ3(vlist);

        double interQuartileRange = q3 - q1;

        double upperOutlierThreshold = q3 + (interQuartileRange * 1.5);
        double lowerOutlierThreshold = q1 - (interQuartileRange * 1.5);

        double upperFaroutThreshold = q3 + (interQuartileRange * 2.0);
        double lowerFaroutThreshold = q1 - (interQuartileRange * 2.0);

        double minRegularValue = Double.POSITIVE_INFINITY;
        double maxRegularValue = Double.NEGATIVE_INFINITY;
        double minOutlier = Double.POSITIVE_INFINITY;
        double maxOutlier = Double.NEGATIVE_INFINITY;
        List outliers = new ArrayList();

        Iterator iterator = vlist.iterator();
        while (iterator.hasNext()) {
            Number number = (Number) iterator.next();
            double value = number.doubleValue();
            if (value > upperOutlierThreshold) {
                outliers.add(number);
                if (value > maxOutlier && value <= upperFaroutThreshold) {
                    maxOutlier = value;
                }
            }
            else if (value < lowerOutlierThreshold) {
                outliers.add(number);
                if (value < minOutlier && value >= lowerFaroutThreshold) {
                    minOutlier = value;
                }
            }
            else {
                minRegularValue = Math.min(minRegularValue, value);
                maxRegularValue = Math.max(maxRegularValue, value);
            }
            minOutlier = Math.min(minOutlier, minRegularValue);
            maxOutlier = Math.max(maxOutlier, maxRegularValue);
        }

        return new BoxAndWhiskerItem(mean, median, q1, q3, minRegularValue,
                maxRegularValue, minOutlier, maxOutlier, outliers);

    }

    /**
     * Calculates the first quartile for a list of numbers in ascending order.
     * If the items in the list are not in ascending order, the result is
     * unspecified.  If the list contains items that are {@code null}, not
     * an instance of {@code Number}, or equivalent to
     * {@code Double.NaN}, the result is unspecified.
     *
     * @param values  the numbers in ascending order ({@code null} not
     *     permitted).
     *
     * @return The first quartile.
     */
    public static double calculateQ1(List values) {
        Args.nullNotPermitted(values, "values");

        double result = Double.NaN;
        int count = values.size();
        if (count > 0) {
            if (count % 2 == 1) {
                if (count > 1) {
                    result = Statistics.calculateMedian(values, 0, count / 2);
                }
                else {
                    result = Statistics.calculateMedian(values, 0, 0);
                }
            }
            else {
                result = Statistics.calculateMedian(values, 0, count / 2 - 1);
            }

        }
        return result;
    }

    /**
     * Calculates the third quartile for a list of numbers in ascending order.
     * If the items in the list are not in ascending order, the result is
     * unspecified.  If the list contains items that are {@code null}, not
     * an instance of {@code Number}, or equivalent to
     * {@code Double.NaN}, the result is unspecified.
     *
     * @param values  the list of values ({@code null} not permitted).
     *
     * @return The third quartile.
     */
    public static double calculateQ3(List values) {
        Args.nullNotPermitted(values, "values");
        double result = Double.NaN;
        int count = values.size();
        if (count > 0) {
            if (count % 2 == 1) {
                if (count > 1) {
                    result = Statistics.calculateMedian(values, count / 2,
                            count - 1);
                }
                else {
                    result = Statistics.calculateMedian(values, 0, 0);
                }
            }
            else {
                result = Statistics.calculateMedian(values, count / 2,
                        count - 1);
            }
        }
        return result;
    }

}