/*
 *    GeoTools - The Open Source Java GIS Toolkit
 *    http://geotools.org
 * 
 *    (C) 2004-2008, 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.resources;

import java.io.Serializable;
import java.util.AbstractList;
import org.geotools.util.CheckedCollection;


/**
 * An unmodifiable view of an array. Invoking
 *
 * <blockquote><code>
 * UnmodifiableArrayList.wrap(array);
 * </code></blockquote>
 *
 * is equivalent to
 *
 * <blockquote><code>
 * {@linkplain Collections#unmodifiableList Collections.unmodifiableList}({@linkplain
 * Arrays#asList Arrays.asList}(array)));
 * </code></blockquote>
 *
 * But this class provides a very slight performance improvement since it uses one less level
 * of indirection.
 *
 * @param <E> The type of elements in the list.
 *
 * @since 2.1
 *
 * @source $URL$
 * @version $Id$
 * @author Martin Desruisseaux (IRD)
 */
public class UnmodifiableArrayList<E> extends AbstractList<E>
        implements CheckedCollection<E>, Serializable
{
    /**
     * For compatibility with different versions.
     */
    private static final long serialVersionUID = -3605810209653785967L;

    /**
     * The wrapped array.
     */
    private final E[] array;

    /**
     * Creates a new instance of an array list. A direct reference to the given array is retained
     * (i.e. the array is <strong>not</strong> cloned). Consequently the given array should not
     * be modified after construction if this list is intented to be immutable.
     * <p>
     * This constructor is for subclassing only. Users should invoke the {@link #wrap} static
     * factory method, which provides more convenient handling of parameterized types.
     *
     * @param array The array to wrap.
     */
    protected UnmodifiableArrayList(final E[] array) {
        this.array = array;
    }

    /**
     * Creates a new instance of an array list. A direct reference to the given array is retained
     * (i.e. the array is <strong>not</strong> cloned). Consequently the given array should not
     * be modified after construction if this list is intented to be immutable.
     *
     * @param  <E> The type of elements in the list.
     * @param  array The array to wrap.
     * @return The given array wrapped in an unmodifiable list.
     *
     * @since 2.5
     */
    public static <E> UnmodifiableArrayList<E> wrap(final E[] array) {
        return new UnmodifiableArrayList<E>(array);
    }

    /**
     * Returns the element type of the wrapped array.
     *
     * @return The type of elements in the list.
     */
    @SuppressWarnings("unchecked") // Safe if this instance was created safely with wrap(E[]).
    public Class<E> getElementType() {
        return (Class) array.getClass().getComponentType();
    }

    /**
     * Returns the list size.
     */
    public int size() {
        return array.length;
    }

    /**
     * Returns the element at the specified index.
     */
    public E get(final int index) {
        return array[index];
    }

    /**
     * Returns the index in this list of the first occurence of the specified
     * element, or -1 if the list does not contain this element. This method
     * is overridden only for performance reason (the default implementation
     * would work as well).
     *
     * @param object The element to search for.
     */
    @Override
    public int indexOf(final Object object) {
        if (object == null) {
            for (int i=0; i<array.length; i++) {
                if (array[i] == null) {
                    return i;
                }
            }
        } else {
            for (int i=0; i<array.length; i++) {
                if (object.equals(array[i])) {
                    return i;
                }
            }
        }
        return -1;
    }

    /**
     * Returns the index in this list of the last occurence of the specified
     * element, or -1 if the list does not contain this element. This method
     * is overridden only for performance reason (the default implementation
     * would work as well).
     *
     * @param object The element to searcch for.
     */
    @Override
    public int lastIndexOf(final Object object) {
        int i = array.length;
        if (object == null) {
            while (--i >= 0) {
                if (array[i] == null) {
                    break;
                }
            }
        } else {
            while (--i >= 0) {
                if (object.equals(array[i])) {
                    break;
                }
            }
        }
        return i;
    }

    /**
     * Returns {@code true} if this collection contains the specified element.
     * This method is overridden only for performance reason (the default implementation
     * would work as well).
     *
     * @param object The element to check for existence.
     */
    @Override
    public boolean contains(final Object object) {
        int i = array.length;
        if (object == null) {
            while (--i >= 0) {
                if (array[i] == null) {
                    return true;
                }
            }
        } else {
            while (--i >= 0) {
                if (object.equals(array[i])) {
                    return true;
                }
            }
        }
        return false;
    }
}