/*
 * BSTEnumerator.java - Enumerate A BST
 *
 * Copyright (c) 1996 Chuck McManis, All Rights Reserved.
 *
 * Permission to use, copy, modify, and distribute this software
 * and its documentation for NON-COMMERCIAL purposes and without
 * fee is hereby granted provided that this copyright notice
 * appears in all copies.
 *
 * CHUCK MCMANIS MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE
 * SUITABILITY OF THE SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING
 * BUT NOT LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT. CHUCK MCMANIS
 * SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT
 * OF USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR ITS DERIVATIVES.
 */

import java.util.Enumeration;
import java.util.NoSuchElementException;

/**
 * This class is used to enumerate a BST from the first to the last node.
 */

class BSTEnumerator extends BSTNode implements Enumeration {
    private BSTNode currentNode;
    private boolean keys;
    private boolean firstNode;

    BSTEnumerator(BSTNode start, boolean doKeys) {
        super();
        currentNode = start;
        keys = doKeys;
        firstNode = true;
    }

    public boolean hasMoreElements() {
        if (firstNode)
            return true;
        if (currentNode != null)
            return (currentNode.successor() != null);
        return false;
    }

    public Object nextElement() {
        if (firstNode) {
            firstNode = false;
        } else if (currentNode != null) {
            currentNode = currentNode.successor();
        }
        if (currentNode == null)
            throw new NoSuchElementException();
        return (keys ? currentNode.key : currentNode.payload);
    }
}