/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.math.genetics;

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

/**
 * Chromosome represented by an immutable list of a fixed length.
 * 
 * @param <T>
 *            type of the representation list
 * @version $Revision:$ $Date:$
 * @since 2.0
 */
public abstract class AbstractListChromosome<T> extends Chromosome {

	/** List representing the chromosome */
	private final List<T> representation;

	/**
	 * Constructor.
	 * 
	 * @param representation
	 *            inner representation of the chromosome
	 */
	public AbstractListChromosome(final List<T> representation) {
		try {
			checkValidity(representation);
		} catch (InvalidRepresentationException e) {
			throw new IllegalArgumentException(
					String.format("Invalid representation for %s", getClass().getSimpleName()), e);
		}
		this.representation = Collections.unmodifiableList(new ArrayList<T>(representation));
	}

	/**
	 * Constructor.
	 * 
	 * @param representation
	 *            inner representation of the chromosome
	 */
	public AbstractListChromosome(final T[] representation) {
		this(Arrays.asList(representation));
	}

	/**
	 * 
	 * Asserts that <code>representation</code> can represent a valid
	 * chromosome.
	 * 
	 * @param representation
	 *            representation of the chromosome
	 * @throws InvalidRepresentationException
	 *             iff the <code>representation</code> can not represent a valid
	 *             chromosome
	 */
	protected abstract void checkValidity(List<T> representation) throws InvalidRepresentationException;

	/**
	 * Returns the (immutable) inner representation of the chromosome.
	 * 
	 * @return the representation of the chromosome
	 */
	protected List<T> getRepresentation() {
		return representation;
	}

	/**
	 * Returns the length of the chromosome.
	 * 
	 * @return the length of the chromosome
	 */
	public int getLength() {
		return getRepresentation().size();
	}

	/**
	 * Creates a new instance of the same class as <code>this</code> is, with a
	 * given <code>arrayRepresentation</code>. This is needed in crossover and
	 * mutation operators, where we need a new instance of the same class, but
	 * with different array representation.
	 * 
	 * Usually, this method just calls a constructor of the class.
	 * 
	 * @param representation
	 *            the inner array representation of the new chromosome.
	 * @return new instance extended from FixedLengthChromosome with the given
	 *         arrayRepresentation
	 */
	public abstract AbstractListChromosome<T> newFixedLengthChromosome(final List<T> representation);

	/**
	 * {@inheritDoc}
	 */
	@Override
	public String toString() {
		return String.format("(f=%s %s)", getFitness(), getRepresentation());
	}
}
