/*
 *    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.feature.visitor;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

import org.geotools.data.simple.SimpleFeatureCollection;
import org.opengis.feature.simple.SimpleFeature;
import org.opengis.filter.expression.Expression;

/**
 * Obtains the data needed for a Quantile operation (classification of features into classes of equal size). 
 * 
 * The result contains an array of lists with the expression values in each.
 * 
 * @author Cory Horner, Refractions Research Inc.
 *
 *
 * @source $URL$
 */
public class QuantileListVisitor implements FeatureCalc {
	private Expression expr;
	private int count = 0;
	private int bins;
	private List items = new ArrayList();
	private List[] bin;

    boolean visited = false;
    int countNull = 0;
    int countNaN = 0;
	
	public QuantileListVisitor(Expression expr, int bins) {
		this.expr = expr;
		this.bins = bins;
		this.bin = new ArrayList[bins];
	}

	public void init(SimpleFeatureCollection collection) {
		//do nothing
	}
	
	public CalcResult getResult() {
	    if (bins == 0 || count == 0) {
	    	return CalcResult.NULL_RESULT;
	    }
        
        // sort the list
		Collections.sort(items);

		if (bins > count) { //resize
			bins = count;
			this.bin = new ArrayList[bins];
		}
		
		// calculate number of items to put into each of the larger bins
		int binPop = new Double(Math.ceil((double) count / bins)).intValue();
		// determine index of bin where the next bin has one less item
		int lastBigBin = count % bins;
		if (lastBigBin == 0) lastBigBin = bins;
		else lastBigBin--;

		// put the items into their respective bins
		int item = 0;
		for (int binIndex = 0; binIndex < bins; binIndex++) {
			bin[binIndex] = new ArrayList();
			for (int binMember = 0; binMember < binPop; binMember++) {
				bin[binIndex].add(items.get(item++));
			}
			if (lastBigBin == binIndex)
				binPop--; // decrease the number of items in a bin for the next item
		}
		return new AbstractCalcResult() {
			public Object getValue() {
				return bin;
			}
		};
	}

	public void visit(SimpleFeature feature) {
        visit((org.opengis.feature.Feature)feature);
    }
    public void visit(org.opengis.feature.Feature feature) {
        Object value = expr.evaluate(feature);

        if (value == null) {
			countNull++; // increment the null count
			return; // don't store this value
		}

		if (value instanceof Double) {
			double doubleVal = ((Double) value).doubleValue();
			if (Double.isNaN(doubleVal) || Double.isInfinite(doubleVal)) {
				countNaN++; // increment the NaN count
				return; // don't store NaN value
			}
		}
		
		count++;
		items.add(value);
	}
	
	public void reset(int bins) {
		this.bins = bins;
		this.count = 0;
		this.items = new ArrayList();
		this.bin = new ArrayList[bins];
	    this.countNull = 0;
	    this.countNaN = 0;
	}

    /**
     * @return the number of features which returned a NaN
     */
    public int getNaNCount() {
    	return countNaN;
    }
    
    /**
     * @return the number of features which returned a null
     */
    public int getNullCount() {
    	return countNull;
    }
}