/*
 * Copyright 1999-2001,2004 The Apache Software Foundation.
 *
 * Licensed 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.jexl.util;



import java.util.Iterator;
import java.util.NoSuchElementException;
import java.lang.reflect.Array;


/**
 *  <p>
 *  An Iterator wrapper for an Object[]. This will
 *  allow us to deal with all array like structures
 *  in a consistent manner.
 *  </p>
 *  <p>
 *  WARNING : this class's operations are NOT synchronized.
 *  It is meant to be used in a single thread, newly created
 *  for each use in the #foreach() directive.
 *  If this is used or shared, synchronize in the
 *  next() method.
 *  </p>
 *
 * @since 1.0
 * @author <a href="mailto:jvanzyl@apache.org">Jason van Zyl</a>
 * @author <a href="mailto:geirm@apache.org">Geir Magnusson Jr.</a>
 * @version $Id: ArrayIterator.java 398329 2006-04-30 12:51:43Z dion $
 */
public class ArrayIterator implements Iterator {
    /**
     * The objects to iterate over.
     */
    private final Object array;

    /**
     * The current position and size in the array.
     */
    private int pos;

    /**
     * The size of the array.
     */
    private final int size;

    /**
     * Creates a new iterator instance for the specified array.
     *
     * @param arr The array for which an iterator is desired.
     */
    public ArrayIterator(Object arr) {
        /*
         * if this isn't an array, then throw.  Note that this is 
         * for internal use - so this should never happen - if it does
         *  we screwed up.
         */
         
        if (!arr.getClass().isArray()) {
            throw new IllegalArgumentException("Programmer error :"
                      + " internal ArrayIterator invoked w/o array");
        }
            
        array = arr;
        pos = 0;
        size = Array.getLength(array);
    }

    /**
     * Move to next element in the array.
     *
     * @return The next object in the array.
     */
    public Object next() {
        if (pos < size) {
            return Array.get(array, pos++);
        }
                
        /*
         *  we screwed up...
         */
         
        throw new NoSuchElementException("No more elements: " + pos
                                         + " / " + size);
    }
    
    /**
     * Check to see if there is another element in the array.
     *
     * @return Whether there is another element.
     */
    public boolean hasNext() {
        return (pos < size);
    }

    /**
     * No op--merely added to satify the <code>Iterator</code> interface.
     */
    public void remove() {
        throw new UnsupportedOperationException();
    }
}
