(function()
{
	var _element = null;

	function _config(pObj, pEvent, pHandler)
	{
		if ( typeof pObj == 'object' )
		{
			if ( pEvent.substring(0, 2) == 'on' )
				pEvent = pEvent.substring(2, pEvent.length);

			if ( arguments.length == 3 )
			{
				if ( pObj.addEventListener )
					pObj.addEventListener(pEvent, pHandler, false);
				else if ( pObj.attachEvent )
					pObj.attachEvent('on' + pEvent, pHandler);
			}
			else if ( arguments.length == 4 )
			{
				if ( pObj.removeEventListener )
					pObj.removeEventListener(pEvent, pHandler, false);
				else if ( pObj.detachEvent )
					pObj.detachEvent('on' + pEvent, pHandler);
			}
		}
	}

	function _getMouseOffset(e, el)
	{
		var docPos = _getPosition(el);
		var mousePos = _mouseCoords(e);
		return {
			'x' : mousePos.x - docPos.x,
			'y' : mousePos.y - docPos.y
		};
	}

	function _getPosition(_pObject)
	{
		var left = 0;
		var top  = 0;

		while ( _pObject.offsetParent )
		{
			left += _pObject.offsetLeft;
			top  += _pObject.offsetTop;
			_pObject = _pObject.offsetParent;
		}

		left += _pObject.offsetLeft;
		top  += _pObject.offsetTop;

		return {
			'x' : left,
			'y' : top
		};
	}

	function _mouseCoords(ev)
	{
		var CoordX = "";
		var CoordY = "";

		if ( ev.pageX || ev.pageY )
			return {
				'x' : ev.pageX,
				'y' : ev.pageY
			};

		CoordX = ev.clientX + document.body.scrollLeft - document.body.clientLeft;
		CoordY = ev.clientY + document.body.scrollTop  - document.body.clientTop;
		return {
			'x' : CoordX,
			'y' : CoordY
		};
	}

	function _mouseMove(e)
	{
		if ( _element )
		{
			if ( _element.mouseOffset == null )
				_element.mouseOffset = _getMouseOffset(e, _element);

			var mousePos = _mouseCoords(e);

			var x = mousePos.x - _element.mouseOffset.x;
			var y = mousePos.y - _element.mouseOffset.y;
			_element.style.left = (( x < 0 ) ? 0 : x) + 'px';
			_element.style.top  = (( y < 0 ) ? 0 : y) + 'px';
		}
	}

	function _mouseUp()
	{
		if ( _element )
		{
			_config(_element, 'onmousemove', _mouseMove, 'remove');
			_config(top.document, 'onmousemove', _mouseMove, 'remove');

			_config(_element, 'onmouseup', _mouseUp, 'remove');
			_config(top.document, 'onmouseup', _mouseUp, 'remove');

			_element.mouseOffset = null;
			_element = null;
		}
	}

	function _toDrag(el)
	{
		if ( el.getAttribute('dragdrop_parent') == null )
		{
			if ( el.getAttribute('dragdrop_child') != null )
			{
				var children = 0;
				while ( (++children < 5) && (el.getAttribute('dragdrop_parent') == null) )
					el = el.parentNode;
			}
			if ( el.getAttribute('dragdrop_parent') == null )
				el = false;
		}
		return el;
	}

	function _drag(e)
	{
		if (typeof e.preventDefault != 'undefined')
			e.preventDefault();
		else
			e.onselectstart = new Function("return false;");

		var el = ( e.target ) ? e.target : e.srcElement;

		el = _toDrag(el);

		if ( el )
		{
			_element = el;

			_config(el, 'onmousemove', _mouseMove);
			_config(top.document, 'onmousemove', _mouseMove);

			_config(el, 'onmouseup', _mouseUp);
			_config(top.document, 'onmouseup', _mouseUp);
		}
	}

	function _set(_pObject)
	{
		if ( typeof _pObject != 'object' )
			return false;

		_pObject.setAttribute('dragdrop_parent', 'true');

		_config(_pObject, 'onmousedown', _drag);
	}

	function DragDrop()
	{
	}

	DragDrop.prototype.drag = _set;
	window.DragDrop = DragDrop;
}
)();