/*
 * 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());
    }
}
