package de.intevation.gnv.chart;

import java.text.NumberFormat;
import java.text.ParseException;

import java.util.Locale;
import java.util.Map;

import org.apache.log4j.Logger;

import org.jfree.chart.ChartTheme;

import org.jfree.chart.plot.XYPlot;

import org.jfree.data.statistics.HistogramDataset;

/**
 * Default implementation of {@link de.intevation.gnv.chart.AbstractHistogram}.
 *
 * @author <a href="mailto:ingo.weinzierl@intevation.de">Ingo Weinzierl</a>
 */
public class DefaultHistogram
extends      AbstractHistogram
{
    /**
     * Default bin count.
     * TODO find a better default value
     */
    public static final int DEFAULT_BINS = 15;

    /**
     * Constant field for limitating the number of bin in a single histogram.
     */
    public static final int MAXIMAL_BINS = 20;

    /**
     * Default key to retrieve the number of bins from {@link
     * #requestParameter}.
     */
    public static final String REQUEST_KEY_BIN_COUNT   = "bincount";

    /**
     * Default key to retrieve the width of a single bin from {@link
     * #requestParameter}.
     */
    public static final String REQUEST_KEY_BIN_WIDTH   = "binwidth";

    /**
     * Default key to retrieve the chart width from {@link #requestParameter}.
     */
    public static final String REQUEST_KEY_CHART_WIDTH = "width";

    /**
     * Default key to retrieve the object from {@link #requestParameter}. It
     * defines which value this chart has to be used for bin calculation. You
     * can either adjust the number of bins or the width of a single bin.
     */
    public static final String REQUEST_KEY_BIN_CHOICE  = "bintype";

    /**
     * Logger used for logging with log4j.
     */
    private static Logger logger = Logger.getLogger(DefaultHistogram.class);

    /**
     * Object storing some further parameter used for chart settings.
     */
    protected Map requestParameter;


    /**
     * Constructor to create DefaultHistogram objects.
     *
     * @param labels Labels to decorate this chart.
     * @param data Raw data to be displayed in histogram.
     * @param theme Theme used to adjust the chart look.
     * @param requestParameter Object which serves some further settings.
     */
    public DefaultHistogram(
        ChartLabels labels, Object[] data, ChartTheme theme, Map requestParameter
    ) {
        super(labels, data, theme);
        this.requestParameter = requestParameter;
    }


    @Override
    protected void applyDatasets() {
        XYPlot plot = (XYPlot) chart.getPlot();

        // prepare data and create add them to histogram dataset
        String   name   = (String)   data[0];
        double[] values = toDouble((Double[]) data[1]);
        int      bins   = getBinCount(values);

        HistogramDataset dataset = new HistogramDataset();
        dataset.addSeries(name, values, bins);

        plot.setDataset(0, dataset);
    }


    /**
     * Method which scans the hole bunch of values and returns an array with
     * contains min and max value. Min value is stored at position 0, max value
     * is stored at position 1 in that array.
     *
     * @param values Array which contains all values
     *
     * @return Array which contains min and max value
     */
    protected double[] getMinMax(double[] values) {
        double[] minmax = new double[2];
        minmax[0] = Double.MAX_VALUE;
        minmax[1] = Double.MIN_VALUE;

        int length = values.length;
        for (int i = 0; i < length; i++) {
            minmax[0] = values[i] < minmax[0] ? values[i] : minmax[0];
            minmax[1] = values[i] > minmax[1] ? values[i] : minmax[1];
        }

        return minmax;
    }


    /**
     * Turn a Double[] into a double[].
     *
     * @param array Doube[]
     *
     * @return double[]
     */
    protected double[] toDouble(Double[] array) {
        int length      = array.length;
        double[] values = new double[length];

        for(int i = 0; i < length; i++) {
            values[i] = array[i].doubleValue();
        }

        return values;
    }


    /**
     * Method to calculate the number of bins this chart should be parted into.
     * The real calculation takes place in {@link #getBinCountByNumber} and
     * {@link #getBinCountByWidth}. This method switches between these methods
     * depending on the object stored in {@link #requestParameter}.
     *
     * @param values All values used in this histogram
     *
     * @return Number of bins
     */
    protected int getBinCount(double[] values) {
        String param = (String) requestParameter.get(REQUEST_KEY_BIN_CHOICE);

        if (param != null && param.equalsIgnoreCase(REQUEST_KEY_BIN_WIDTH)) {
            return getBinCountByWidth(values);
        }
        else {
            return getBinCountByNumber();
        }
    }


    /**
     * Method to retrieve the number of bins. If {@link #requestParameter}
     * contains a valid <code>Integer</code> at
     * <code>REQUEST_KEY_BIN_COUNT</code> and this is smaller than or equal
     * {@link #MAXIMAL_BINS}, this value is used. If no valid
     * <code>Integer</code> is given or if the value in {@link #requestParameter}
     * is bigger than {@link #MAXIMAL_BINS}, {@link #DEFAULT_BINS} is used.
     *
     * @return Number of bins
     */
    protected int getBinCountByNumber() {
        int    bins  = -1;
        String param = (String) requestParameter.get(REQUEST_KEY_BIN_COUNT);

        try {
            bins = Integer.parseInt(param);
            bins = bins <= 0 ? DEFAULT_BINS : bins;
            bins = bins >  MAXIMAL_BINS ? MAXIMAL_BINS : bins;

            return bins;
        }
        catch (NumberFormatException nfe) {
            logger.warn("Invalid number of bins for histogram chart: " + param);
            logger.warn("Return default bins: " + DEFAULT_BINS);

            return DEFAULT_BINS;
        }
    }


    /**
     * Serves the number of bins depending on a given width for each bin, but
     * maximum bin count is limited by {@link #MAXIMAL_BINS}.
     *
     * @param values All values in this histogram
     *
     * @return Number of bins
     */
    protected int getBinCountByWidth(double[] values) {
        int    bins   = -1;
        String param  = (String) requestParameter.get(REQUEST_KEY_BIN_WIDTH);

        double[] minmax     = getMinMax(values);
        double   totalWidth = minmax[1] - minmax[0];
        double   binWidth   = Double.parseDouble(param);

        double tmpBins = totalWidth / binWidth;

        bins = (int) Math.round(tmpBins);
        bins = bins <= 0 ? DEFAULT_BINS : bins;
        bins = bins >  MAXIMAL_BINS ? MAXIMAL_BINS : bins;

        return bins;
    }
}
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