/*
 * 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.stgp.stat;

import org.epochx.event.GenerationEvent.EndGeneration;
import org.epochx.event.stat.AbstractStat;

/**
 * A stat that returns the minimum length of all the program trees in the
 * population from the previous completed generation. All individuals in the
 * population must be instances of <code>STGPIndividual</code>.
 * 
 * @see GenerationMaximumLength
 * 
 * @since 2.0
 */
public class GenerationMinimumLength extends AbstractStat<EndGeneration> {

	private int min;

	/**
	 * Constructs a <code>GenerationMinimumLength</code> stat and registers its
	 * dependencies
	 */
	public GenerationMinimumLength() {
		super(GenerationLengths.class);
	}

	/**
	 * Triggers the generation of an updated value for this stat. Once this stat
	 * has been registered, this method will be called on each
	 * <code>EndGeneration</code> event.
	 * 
	 * @param event an object that encapsulates information about the event that
	 *        occurred
	 */
	@Override
	public void refresh(EndGeneration event) {
		int[] lengths = AbstractStat.get(GenerationLengths.class).getLengths();
		min = Integer.MAX_VALUE;

		for (int length: lengths) {
			if (length < min) {
				min = length;
			}
		}
	}

	/**
	 * Returns the minimum length of the program trees in the previous
	 * generation
	 * 
	 * @return the minimum length of the program trees
	 */
	public int getMinimum() {
		return min;
	}

	/**
	 * Returns a string representation of the value of this stat
	 * 
	 * @return a <code>String</code> that represents the value of this stat
	 */
	@Override
	public String toString() {
		return Integer.toString(min);
	}
}