/*
 *    GeoTools - The Open Source Java GIS Toolkit
 *    http://geotools.org
 * 
 *    (C) 2005-2008, Open Source Geospatial Foundation (OSGeo)
 *    
 *    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;
 *    version 2.1 of the License.
 *
 *    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.
 */
package org.geotools.filter.function;

import java.io.IOException;
import java.util.logging.Level;

import org.geotools.data.simple.SimpleFeatureCollection;
import org.geotools.feature.FeatureCollection;
import org.geotools.feature.visitor.AverageVisitor;
import org.geotools.feature.visitor.CalcResult;
import org.geotools.feature.visitor.StandardDeviationVisitor;
import org.geotools.util.NullProgressListener;

/**
 * Breaks a SimpleFeatureCollection into classes using the standard deviation classification method.
 * 
 * @author Cory Horner, Refractions Research Inc.
 *
 * @source $URL$
 */
public class StandardDeviationFunction extends ClassificationFunction {

    public int getArgCount() {
        return 2;
    }
    
	public StandardDeviationFunction() {
        setName("StandardDeviation");
	}

	private Object calculate(SimpleFeatureCollection featureCollection) {
        try {
            int classNum = getClasses();
    		// find the average
    		AverageVisitor averageVisit = new AverageVisitor(getExpression());
    		if (progress == null) progress = new NullProgressListener();
                featureCollection.accepts(averageVisit, progress);
    		if (progress.isCanceled()) return null;
    		CalcResult calcResult = averageVisit.getResult();
    		if (calcResult == null) return null;
    		double average = calcResult.toDouble();
    		// find the standard deviation
    		StandardDeviationVisitor sdVisit = new StandardDeviationVisitor(getExpression(), average);
    		featureCollection.accepts(sdVisit, progress);
    		if (progress.isCanceled()) return null;
    		calcResult = sdVisit.getResult();
    		if (calcResult == null) return null;
    		double standardDeviation = calcResult.toDouble();
            //figure out the min and max values
            Double min[] = new Double[classNum];
            Double max[] = new Double[classNum];
            for (int i = 0; i < classNum; i++) {
                min[i] = getMin(i, classNum, average, standardDeviation);
                max[i] = getMax(i, classNum, average, standardDeviation);
            }
            return new RangedClassifier(min, max);
        } catch (IOException e) {
            LOGGER.log(Level.SEVERE, "StandardDeviationFunction calculate failed", e);
            return null;
        }
	}

	public Object evaluate(Object feature) {
		if (!(feature instanceof FeatureCollection)) {
			return null;
		}
        return calculate((SimpleFeatureCollection) feature);
	}

	private Double getMin(int index, int numClasses, double average, double standardDeviation) {
		if (index <= 0 || index >= numClasses)
			return null;
		return new Double(average - (((numClasses / 2.0) - index) * standardDeviation));
	}
	
	private Double getMax(int index, int numClasses, double average, double standardDeviation) {
		if (index < 0 || index >= numClasses - 1)
			return null;
		return new Double(average - (((numClasses / 2.0) - 1 - index) * standardDeviation));
	}
}