package com.vci.client.ui.util;

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

import javax.swing.tree.TreeNode;


public class PostorderEnumeration implements Enumeration<TreeNode> {
	static public final Enumeration<TreeNode> EMPTY_ENUMERATION = new Enumeration<TreeNode>() {
		public boolean hasMoreElements() {
			return false;
		}

		public TreeNode nextElement() {
			throw new NoSuchElementException("No more elements");
		}
	};
	
	protected TreeNode root;
	protected Enumeration<TreeNode> children;
	protected Enumeration<TreeNode> subtree;

	@SuppressWarnings("unchecked")
	public PostorderEnumeration(TreeNode rootNode) {
		super();
		root = rootNode;
		children = root.children();
		subtree = EMPTY_ENUMERATION;
	}

	public boolean hasMoreElements() {
		return root != null;
	}

	public TreeNode nextElement() {
		TreeNode retval;

		if (subtree.hasMoreElements()) {
			retval = subtree.nextElement();
		} else if (children.hasMoreElements()) {
			subtree = new PostorderEnumeration(
					(TreeNode) children.nextElement());
			retval = subtree.nextElement();
		} else {
			retval = root;
			root = null;
		}

		return retval;
	}

} // End of class PostorderEnumeration