/**
 * Simple DOM traversing copied from MooTools.
 */
DOM = function () {
	
	function get(id) {
		if (id && typeof id === 'string') {
			id = document.getElementById(id);
		}
		return id || null;
	}
	
	function walk(element, tag, walk, start, all) {
		var el = get(element)[start || walk], elements = all ? [] : null;
		while (el) {
			if (el.nodeType === 1 && (!tag || el.tagName.toLowerCase() === tag)) {
				if (!all) {
					return el;
				}
				elements.push(el);
			}
			el = el[walk];
		}
		return elements;
	}
	
	return {
		
		// Get the element by its id
		get: get,
		
		walk: walk,
		
		// Returns the previousSibling of the Element (excluding text nodes).
		getPrevious: function (el, tag) {
			return walk(el, tag, 'previousSibling');
		},
		
		// Like getPrevious, but returns a collection of all the matched previousSiblings.
		getAllPrevious: function (el, tag) {
			return walk(el, tag, 'previousSibling', null, true);
		},
		
		// As getPrevious, but tries to find the nextSibling (excluding text nodes).
		getNext: function (el, tag) {
			return walk(el, tag, 'nextSibling');
		},
		
		// Like getNext, but returns a collection of all the matched nextSiblings.
		getAllNext: function (el, tag) {
			return walk(el, tag, 'nextSibling', null, true);
		},
		
		// Works as getPrevious, but tries to find the firstChild (excluding text nodes).
		getFirst: function (el, tag) {
			return walk(el, tag, 'nextSibling', 'firstChild');
		},
		
		// Works as getPrevious, but tries to find the lastChild.
		getLast: function (el, tag) {
			return walk(el, tag, 'previousSibling', 'lastChild');
		},
		
		// Works as getPrevious, but tries to find the parentNode.
		getParent: function (el, tag) {
			return walk(el, tag, 'parentNode');
		},
		
		// Like getParent, but returns a collection of all the matched parentNodes up the tree.
		getParents: function (el, tag) {
			return walk(el, tag, 'parentNode', null, true);
		},
		
		// Returns all the Element's children (excluding text nodes).
		getChildren: function (el, tag) {
			return walk(el, tag, 'nextSibling', 'firstChild', true);
		},
		
		// Removes the Element from the DOM.
		dispose: function (el) {
			el = get(el);
			return (el.parentNode) ? el.parentNode.removeChild(el) : el;
		}
		
	};
}();