/**
 * TreeWalker.js
 *
 * Copyright 2009, Moxiecode Systems AB
 * Released under LGPL License.
 *
 * License: http://tinymce.moxiecode.com/license
 * Contributing: http://tinymce.moxiecode.com/contributing
 */

tinymce.dom.TreeWalker = function(start_node, root_node) {
	var node = start_node;

	function findSibling(node, start_name, sibling_name, shallow) {
		var sibling, parent;

		if (node) {
			// Walk into nodes if it has a start
			if (!shallow && node[start_name])
				return node[start_name];

			// Return the sibling if it has one
			if (node != root_node) {
				sibling = node[sibling_name];
				if (sibling)
					return sibling;

				// Walk up the parents to look for siblings
				for (parent = node.parentNode; parent && parent != root_node; parent = parent.parentNode) {
					sibling = parent[sibling_name];
					if (sibling)
						return sibling;
				}
			}
		}
	};

	/**
	 * Returns the current node.
	 *
	 * @return {Node} Current node where the walker is.
	 */
	this.current = function() {
		return node;
	};

	/**
	 * Walks to the next node in tree.
	 *
	 * @return {Node} Current node where the walker is after moving to the next node.
	 */
	this.next = function(shallow) {
		return (node = findSibling(node, 'firstChild', 'nextSibling', shallow));
	};

	/**
	 * Walks to the previous node in tree.
	 *
	 * @return {Node} Current node where the walker is after moving to the previous node.
	 */
	this.prev = function(shallow) {
		return (node = findSibling(node, 'lastChild', 'previousSibling', shallow));
	};
};