/* ===========================================================
 * JFreeChart : a free chart library for the Java(tm) platform
 * ===========================================================
 *
 * (C) Copyright 2000-2007, by Object Refinery Limited and Contributors.
 *
 * Project Info:  http://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.  
 *
 * [Java is a trademark or registered trademark of Sun Microsystems, Inc. 
 * in the United States and other countries.]
 *
 * ------------------
 * MovingAverage.java
 * ------------------
 * (C) Copyright 2003-2007, by Object Refinery Limited.
 *
 * Original Author:  David Gilbert (for Object Refinery Limited);
 * Contributor(s):   Benoit Xhenseval;
 *
 * Changes
 * -------
 * 28-Jan-2003 : Version 1 (DG);
 * 10-Mar-2003 : Added createPointMovingAverage() method contributed by Benoit 
 *               Xhenseval (DG);
 * 01-Aug-2003 : Added new method for TimeSeriesCollection, and fixed bug in 
 *               XYDataset method (DG);
 * 15-Jul-2004 : Switched getX() with getXValue() and getY() with 
 *               getYValue() (DG);
 * 11-Jan-2005 : Removed deprecated code in preparation for the 1.0.0 
 *               release (DG);
 *
 */

package org.jfree.data.time;

import org.jfree.data.xy.XYDataset;
import org.jfree.data.xy.XYSeries;
import org.jfree.data.xy.XYSeriesCollection;

/**
 * A utility class for calculating moving averages of time series data.
 */
public class MovingAverage {

    /**
     * Creates a new {@link TimeSeriesCollection} containing a moving average 
     * series for each series in the source collection.
     * 
     * @param source  the source collection.
     * @param suffix  the suffix added to each source series name to create the
     *                corresponding moving average series name.
     * @param periodCount  the number of periods in the moving average 
     *                     calculation.
     * @param skip  the number of initial periods to skip.
     * 
     * @return A collection of moving average time series.
     */
    public static TimeSeriesCollection createMovingAverage(
        TimeSeriesCollection source, String suffix, int periodCount,
        int skip) {
    
        // check arguments
        if (source == null) {
            throw new IllegalArgumentException(
                "MovingAverage.createMovingAverage() : null source."
            );
        }

        if (periodCount < 1) {
            throw new IllegalArgumentException(
                "periodCount must be greater than or equal to 1."
            );
        }

        TimeSeriesCollection result = new TimeSeriesCollection();
        
        for (int i = 0; i < source.getSeriesCount(); i++) {
            TimeSeries sourceSeries = source.getSeries(i);
            TimeSeries maSeries = createMovingAverage(
                sourceSeries, sourceSeries.getKey() + suffix, periodCount, skip
            );
            result.addSeries(maSeries);       
        }
        
        return result;
        
    }
    
    /**
     * Creates a new {@link TimeSeries} containing moving average values for 
     * the given series.  If the series is empty (contains zero items), the 
     * result is an empty series.
     *
     * @param source  the source series.
     * @param name  the name of the new series.
     * @param periodCount  the number of periods used in the average 
     *                     calculation.
     * @param skip  the number of initial periods to skip.
     *
     * @return The moving average series.
     */
    public static TimeSeries createMovingAverage(TimeSeries source,
                                                 String name,
                                                 int periodCount,
                                                 int skip) {

        // check arguments
        if (source == null) {
            throw new IllegalArgumentException("Null source.");
        }

        if (periodCount < 1) {
            throw new IllegalArgumentException(
                "periodCount must be greater than or equal to 1."
            );

        }

        TimeSeries result = new TimeSeries(name, source.getTimePeriodClass());

        if (source.getItemCount() > 0) {

            // if the initial averaging period is to be excluded, then 
            // calculate the index of the
            // first data item to have an average calculated...
            long firstSerial 
                = source.getDataItem(0).getPeriod().getSerialIndex() + skip;

            for (int i = source.getItemCount() - 1; i >= 0; i--) {

                // get the current data item...
                TimeSeriesDataItem current = source.getDataItem(i);
                RegularTimePeriod period = current.getPeriod();
                long serial = period.getSerialIndex();

                if (serial >= firstSerial) {
                    // work out the average for the earlier values...
                    int n = 0;
                    double sum = 0.0;
                    long serialLimit = period.getSerialIndex() - periodCount;
                    int offset = 0;
                    boolean finished = false;

                    while ((offset < periodCount) && (!finished)) {
                        if ((i - offset) >= 0) {
                            TimeSeriesDataItem item 
                                = source.getDataItem(i - offset);
                            RegularTimePeriod p = item.getPeriod();
                            Number v = item.getValue();
                            long currentIndex = p.getSerialIndex();
                            if (currentIndex > serialLimit) {
                                if (v != null) {
                                    sum = sum + v.doubleValue();
                                    n = n + 1;
                                }
                            }
                            else {
                                finished = true;
                            }
                        }
                        offset = offset + 1;
                    }
                    if (n > 0) {
                        result.add(period, sum / n);
                    }
                    else {
                        result.add(period, null);
                    }
                }

            }
        }

        return result;

    }

    /**
     * Creates a new {@link TimeSeries} containing moving average values for 
     * the given series, calculated by number of points (irrespective of the 
     * 'age' of those points).  If the series is empty (contains zero items), 
     * the result is an empty series.
     * <p>
     * Developed by Benoit Xhenseval (www.ObjectLab.co.uk).
     *
     * @param source  the source series.
     * @param name  the name of the new series.
     * @param pointCount  the number of POINTS used in the average calculation 
     *                    (not periods!)
     *
     * @return The moving average series.
     */
    public static TimeSeries createPointMovingAverage(TimeSeries source,
                                                      String name, 
                                                      int pointCount) {

        // check arguments
        if (source == null) {
            throw new IllegalArgumentException("Null 'source'.");
        }

        if (pointCount < 2) {
            throw new IllegalArgumentException(
                "periodCount must be greater than or equal to 2."
            );
        }

        TimeSeries result = new TimeSeries(name, source.getTimePeriodClass());
        double rollingSumForPeriod = 0.0;
        for (int i = 0; i < source.getItemCount(); i++) {
            // get the current data item...
            TimeSeriesDataItem current = source.getDataItem(i);
            RegularTimePeriod period = current.getPeriod();
            rollingSumForPeriod += current.getValue().doubleValue();

            if (i > pointCount - 1) {
                // remove the point i-periodCount out of the rolling sum.
                TimeSeriesDataItem startOfMovingAvg 
                    = source.getDataItem(i - pointCount);
                rollingSumForPeriod 
                    -= startOfMovingAvg.getValue().doubleValue();
                result.add(period, rollingSumForPeriod / pointCount);
            }
            else if (i == pointCount - 1) {
                result.add(period, rollingSumForPeriod / pointCount);
            }
        }
        return result;
    }

    /**
     * Creates a new {@link XYDataset} containing the moving averages of each 
     * series in the <code>source</code> dataset.
     *
     * @param source  the source dataset.
     * @param suffix  the string to append to source series names to create 
     *                target series names.
     * @param period  the averaging period.
     * @param skip  the length of the initial skip period.
     *
     * @return The dataset.
     */
    public static XYDataset createMovingAverage(XYDataset source, String suffix,
                                                long period, final long skip) {

        return createMovingAverage(
            source, suffix, (double) period, (double) skip
        );
        
    }


    /**
     * Creates a new {@link XYDataset} containing the moving averages of each 
     * series in the <code>source</code> dataset.
     *
     * @param source  the source dataset.
     * @param suffix  the string to append to source series names to create 
     *                target series names.
     * @param period  the averaging period.
     * @param skip  the length of the initial skip period.
     *
     * @return The dataset.
     */
    public static XYDataset createMovingAverage(XYDataset source, String suffix,
                                                double period, double skip) {

        // check arguments
        if (source == null) {
            throw new IllegalArgumentException("Null source (XYDataset).");
        }
        
        XYSeriesCollection result = new XYSeriesCollection();

        for (int i = 0; i < source.getSeriesCount(); i++) {
            XYSeries s = createMovingAverage(
                source, i, source.getSeriesKey(i) + suffix, period, skip
            );
            result.addSeries(s);
        }

        return result;

    }

    /**
     * Creates a new {@link XYSeries} containing the moving averages of one 
     * series in the <code>source</code> dataset.
     *
     * @param source  the source dataset.
     * @param series  the series index (zero based).
     * @param name  the name for the new series.
     * @param period  the averaging period.
     * @param skip  the length of the initial skip period.
     *
     * @return The dataset.
     */
    public static XYSeries createMovingAverage(XYDataset source, 
                                               int series, String name,
                                               double period, double skip) {

                                               
        // check arguments
        if (source == null) {
            throw new IllegalArgumentException("Null source (XYDataset).");
        }

        if (period < Double.MIN_VALUE) {
            throw new IllegalArgumentException("period must be positive.");

        }

        if (skip < 0.0) {
            throw new IllegalArgumentException("skip must be >= 0.0.");

        }

        XYSeries result = new XYSeries(name);

        if (source.getItemCount(series) > 0) {

            // if the initial averaging period is to be excluded, then 
            // calculate the lowest x-value to have an average calculated...
            double first = source.getXValue(series, 0) + skip;

            for (int i = source.getItemCount(series) - 1; i >= 0; i--) {

                // get the current data item...
                double x = source.getXValue(series, i);

                if (x >= first) {
                    // work out the average for the earlier values...
                    int n = 0;
                    double sum = 0.0;
                    double limit = x - period;
                    int offset = 0;
                    boolean finished = false;

                    while (!finished) {
                        if ((i - offset) >= 0) {
                            double xx = source.getXValue(series, i - offset);
                            Number yy = source.getY(series, i - offset);
                            if (xx > limit) {
                                if (yy != null) {
                                    sum = sum + yy.doubleValue();
                                    n = n + 1;
                                }
                            }
                            else {
                                finished = true;
                            }
                        }
                        else {
                            finished = true;
                        }
                        offset = offset + 1;
                    }
                    if (n > 0) {
                        result.add(x, sum / n);
                    }
                    else {
                        result.add(x, null);
                    }
                }

            }
        }

        return result;

    }

}