/*
 * Copyright 2007-2013
 * Licensed under GNU Lesser General Public License
 * 
 * This file is part of EpochX
 * 
 * EpochX 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 3 of the License, or
 * (at your option) any later version.
 * 
 * EpochX 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 EpochX. If not, see <http://www.gnu.org/licenses/>.
 * 
 * The latest version is available from: http://www.epochx.org
 */

package org.epochx.event.stat;

import org.epochx.Fitness;
import org.epochx.event.GenerationEvent.EndGeneration;

/**
 * Stat that provides the median fitness. If there are an even number of programs in
 * the population then there are two median values, the first will be returned.
 */
public class GenerationMedianFitness extends AbstractStat<EndGeneration> {

	/**
	 * The median fitness value.
	 */
	private Fitness median;

	/**
	 * Constructs a <code>GenerationMedianFitness</code>.
	 */
	public GenerationMedianFitness() {
		super(GenerationFitnesses.Sorted.class);
	}

	/**
	 * Determines the median fitness value.
	 * 
	 * @param event the <code>EndGeneration</code> event object.
	 */
	@Override
	public void refresh(EndGeneration event) {
		Fitness[] fitnesses = AbstractStat.get(GenerationFitnesses.Sorted.class).getFitnesses();
		
		int medianIndex = (int) Math.floor(fitnesses.length / 2);
		median = fitnesses[medianIndex - 1];
	}

	/**
	 * Returns the median fitness value.
	 * 
	 * @return the median fitness value.
	 */
	public Fitness getMedian() {
		return median;
	}

	/**
	 * Returns a string representation of the median fitness value.
	 * 
	 * @return a string representation of the median fitness value.
	 */
	@Override
	public String toString() {
		return median.toString();
	}
}