var doc = this.document,
inited,
documentElement = doc.documentElement,
round = Math.round, max = Math.max,

// Load-time constants.
IS_BODY_ACTING_ROOT = documentElement && documentElement.clientWidth === 0,

// IE, Safari, and Opera support clientTop. FF 2 doesn't
IS_CLIENT_TOP_SUPPORTED = 'clientTop'in documentElement,

TABLE = /^h/.test(documentElement.tagName) ? "table" : "TABLE",

IS_CURRENT_STYLE_SUPPORTED = 'currentStyle'in documentElement,

// XXX Opera <= 9.2 - parent border widths are included in offsetTop.
IS_PARENT_BODY_BORDER_INCLUDED_IN_OFFSET,

// XXX Opera <= 9.2 - body offsetTop is inherited to children's offsetTop
// when body position is not static.
// opera will inherit the offsetTop/offsetLeft of body for relative offsetParents.

IS_BODY_MARGIN_INHERITED,
IS_BODY_TOP_INHERITED,
IS_BODY_OFFSET_EXCLUDING_MARGIN,

// XXX Mozilla includes a table border in the TD's offsetLeft.
// There is 1 exception:
//   When the TR has position: relative and the TD has block level content.
//   In that case, the TD does not include the TABLE's border in it's offsetLeft.
// We do not account for this peculiar bug.
IS_TABLE_BORDER_INCLUDED_IN_TD_OFFSET,
IS_STATIC_BODY_OFFSET_PARENT_BUT_ABSOLUTE_CHILD_SUBTRACTS_BODY_BORDER_WIDTH,

IS_BODY_OFFSET_IGNORED_WHEN_BODY_RELATIVE_AND_LAST_CHILD_POSITIONED,

IS_CONTAINER_BODY_STATIC_INCLUDING_HTML_PADDING,
IS_CONTAINER_BODY_RELATIVE_INCLUDING_HTML_PADDING_REL_CHILD,
IS_CONTAINER_BODY_RELATIVE_INCLUDING_HTML_PADDING_ABS_CHILD,
IS_CONTAINER_BODY_INCLUDING_HTML_MARGIN,

// In Safari 2.0.4, BODY can have offsetTop when offsetParent is null.
// but offsetParent will be HTML (root) when HTML has position.
// IS_BODY_OFFSET_TOP_NO_OFFSETPARENT,

IS_COMPUTED_STYLE_SUPPORTED = doc.defaultView
&& typeof doc.defaultView.getComputedStyle != "undefined",
getBoundingClientRect = "getBoundingClientRect",
relative = "relative",
borderTopWidth = "borderTopWidth",
borderLeftWidth = "borderLeftWidth",
positionedExp = /^(?:r|a)/,
absoluteExp = /^(?:a|f)/;




Element.addMethods({
	cumulativeOffsetFixed: function(el, container, coords) {
		var doc = el.ownerDocument,
		documentElement = doc.documentElement,
		body = $$('body')[0];

		var el = $(el),
			container = $(container);
		if (!el) {
			return {left: 0, top: 0}
		}

		if(!container)
		container = doc;

		if(!coords)
		coords = {left: 0, top: 0};

		var returnCoords = function(element) {
			return Element._returnOffset(element.cumulativeOffsetLeft, element.cumulativeOffsetTop);
		}

		if (el === container) {
			el.cumulativeOffsetLeft = el.cumulativeOffsetTop = 0
			return returnCoords(el);
		}

		if(getBoundingClientRect in el) {

			// In BackCompat mode, body's border goes to the window. BODY is ICB.
			var rootBorderEl = IS_BODY_ACTING_ROOT ? body : documentElement,
			box = el[getBoundingClientRect](),
			x = box.left + Math.max( documentElement.scrollLeft, body.scrollLeft ),
			y = box.top + Math.max( documentElement.scrollTop, body.scrollTop ),
			bodyCurrentStyle,
			borderTop = rootBorderEl.clientTop,
			borderLeft = rootBorderEl.clientLeft;

			if(IS_CLIENT_TOP_SUPPORTED) {
				x -= borderLeft;
				y -= borderTop;
			}
			if(container !== doc) {
				box = Element.getOffsetCoords(container, null);
				x -= box.x;
				y -= box.y;
				if(IS_BODY_ACTING_ROOT && container === body && IS_CLIENT_TOP_SUPPORTED) {
					x -= borderLeft;
					y -= borderTop;
				}
			}

			if(IS_BODY_ACTING_ROOT && IS_CURRENT_STYLE_SUPPORTED
			&& container != doc && container !== body) {
				bodyCurrentStyle = body.currentStyle;
				x += parseFloat(bodyCurrentStyle.marginLeft)||0 +
				parseFloat(bodyCurrentStyle.left)||0;
				y += parseFloat(bodyCurrentStyle.marginTop)||0 +
				parseFloat(bodyCurrentStyle.top)||0;
			}
			el.cumulativeOffsetLeft = x;
			el.cumulativeOffsetTop = y;
			return returnCoords(el);
		}

		// Crawling up the tree.
		else if(IS_COMPUTED_STYLE_SUPPORTED) {
			if(!inited) Element.cumulativeOffsetFixedInit();

			var offsetLeft = el.offsetLeft,
			offsetTop = el.offsetTop,
			defaultView = doc.defaultView,
			cs = defaultView.getComputedStyle(el, '');
			if(cs.position == "fixed") {
				el.cumulativeOffsetLeft = offsetLeft + documentElement.scrollLeft;
				el.cumulativeOffsetTop = offsetTop + documentElement.scrollTop;
				return returnCoords(el);
			}
			var bcs = defaultView.getComputedStyle(body,''),
			isBodyStatic = !positionedExp.test(bcs.position),
			lastOffsetParent = el,
			parent = el.parentNode,
			offsetParent = el.offsetParent;

			// Main loop -----------------------------------------------------------------------
			// Loop up, gathering scroll offsets on parentNodes.
			// when we get to a parent that's an offsetParent, update
			// the current offsetParent marker.
			for( ; parent && parent !== container; parent = parent.up(0)) {
				if(parent !== body && parent !== documentElement) {
					offsetLeft -= parent.scrollLeft;
					offsetTop -= parent.scrollTop;
				}
				if(parent === offsetParent) {
					// If we get to BODY and have static position, skip it.
					if(parent === body && isBodyStatic);
					else {

						// XXX Mozilla; Exclude static body; if static, it's offsetTop will be wrong.
						// Include parent border widths. This matches behavior of clientRect approach.
						// XXX Opera <= 9.2 includes parent border widths.
						// See IS_PARENT_BODY_BORDER_INCLUDED_IN_OFFSET below.
						if( !IS_PARENT_BODY_BORDER_INCLUDED_IN_OFFSET &&
						! (parent.tagName === TABLE && IS_TABLE_BORDER_INCLUDED_IN_TD_OFFSET)) {
							var pcs = defaultView.getComputedStyle(parent, "");
							// Mozilla doesn't support clientTop. Add borderWidth to the sum.
							offsetLeft += parseFloat(pcs[borderLeftWidth])||0;
							offsetTop += parseFloat(pcs[borderTopWidth])||0;
						}
						if(parent !== body) {
							offsetLeft += offsetParent.offsetLeft;
							offsetTop += offsetParent.offsetTop;
							lastOffsetParent = offsetParent;
							offsetParent = parent.offsetParent; // next marker to check for offsetParent.
						}
					}
				}
			}

			//--------Post - loop, body adjustments----------------------------------------------
			// Complications due to CSSOM Views - the browsers try to implement a contradictory
			// spec: http://www.w3.org/TR/cssom-view/#offset-attributes

			// XXX Mozilla, Safari 3, Opera: body margin is never
			// included in body offsetLeft/offsetTop.
			// This is wrong. Body's offsetTop should work like any other element.
			// In Safari 2.0.4, BODY can have offsetParent, and even
			// if it doesn't, it can still have offsetTop.
			// But Safari 2.0.4 doubles offsetTop for relatively positioned elements
			// and this script does not account for that.

			// XXX Mozilla: When body has a border, body's offsetTop === negative borderWidth;
			// Don't use body.offsetTop.
			var bodyOffsetLeft = 0,
			bodyOffsetTop = 0,
			isLastElementAbsolute,
			isLastOffsetElementPositioned,
			isContainerDocOrDocEl = container === doc || container === documentElement,
			dcs,
			lastOffsetPosition;

			// If the lastOffsetParent is document,
			// it is not positioned (and hence, not absolute).
			if(lastOffsetParent != doc) {
				lastOffsetPosition = defaultView.getComputedStyle(lastOffsetParent,'').position;
				isLastElementAbsolute = absoluteExp.test(lastOffsetPosition);
				isLastOffsetElementPositioned = isLastElementAbsolute ||
				positionedExp.test(lastOffsetPosition);
			}

			// do we need to add margin?
			if(
			(lastOffsetParent === el && el.offsetParent === body && !IS_BODY_MARGIN_INHERITED
			&& container !== body && !(isBodyStatic && IS_BODY_OFFSET_EXCLUDING_MARGIN))
			|| (IS_BODY_MARGIN_INHERITED && lastOffsetParent === el && !isLastOffsetElementPositioned)
			|| !isBodyStatic
			&& isLastOffsetElementPositioned
			&& IS_BODY_OFFSET_IGNORED_WHEN_BODY_RELATIVE_AND_LAST_CHILD_POSITIONED
			&& isContainerDocOrDocEl) {
				bodyOffsetTop += parseFloat(bcs.marginTop)||0;
				bodyOffsetLeft += parseFloat(bcs.marginLeft)||0;
			}

			// Case for padding on documentElement.
			if(container === body) {
				dcs = defaultView.getComputedStyle(documentElement,'');
				if(
				(!isBodyStatic &&
				((IS_CONTAINER_BODY_RELATIVE_INCLUDING_HTML_PADDING_REL_CHILD && !isLastElementAbsolute)
				||
				(IS_CONTAINER_BODY_RELATIVE_INCLUDING_HTML_PADDING_ABS_CHILD && isLastElementAbsolute))
				)
				|| isBodyStatic && IS_CONTAINER_BODY_STATIC_INCLUDING_HTML_PADDING
				) {
					bodyOffsetTop -= parseFloat(dcs.paddingTop)||0;
					bodyOffsetLeft -= parseFloat(dcs.paddingLeft)||0;
				}

				if(IS_CONTAINER_BODY_INCLUDING_HTML_MARGIN){
					if(!isLastOffsetElementPositioned
					|| isLastOffsetElementPositioned && !isBodyStatic)
					bodyOffsetTop -= parseFloat(dcs.marginTop)||0;
					bodyOffsetLeft -= parseFloat(dcs.marginLeft)||0;
				}
			}
			if(isBodyStatic) {
				// XXX Safari subtracts border width of body from element's offsetTop (opera does it, too)
				if(IS_STATIC_BODY_OFFSET_PARENT_BUT_ABSOLUTE_CHILD_SUBTRACTS_BODY_BORDER_WIDTH
				// XXX: Safari will use HTML for containing block (CSS),
				// but will subtract the body's border from the body's absolutely positioned
				// child.offsetTop. Safari reports the child's offsetParent is BODY, but
				// doesn't treat it that way (Safari bug).
				|| (!isLastElementAbsolute && !IS_PARENT_BODY_BORDER_INCLUDED_IN_OFFSET
				&& isContainerDocOrDocEl)) {
					bodyOffsetTop += parseFloat(bcs[borderTopWidth]);
					bodyOffsetLeft += parseFloat(bcs[borderLeftWidth]);
				}
			}

			// body is positioned, and if it excludes margin,
			// it's probably partly using the AVK-CSSOM disaster.
			else if(IS_BODY_OFFSET_EXCLUDING_MARGIN) {
				if(isContainerDocOrDocEl) {
					if(!IS_BODY_TOP_INHERITED) {

						// If the body is positioned, add its left and top value.
						bodyOffsetTop += parseFloat(bcs.top)||0;
						bodyOffsetLeft += parseFloat(bcs.left)||0;

						// XXX: Opera normally include the parentBorder in offsetTop.
						// We have a preventative measure in the loop above.
						if(isLastElementAbsolute && IS_PARENT_BODY_BORDER_INCLUDED_IN_OFFSET) {
							bodyOffsetTop += parseFloat(bcs[borderTopWidth]);
							bodyOffsetLeft += parseFloat(bcs[borderLeftWidth]);
						}
					}

					// Padding on documentElement is not included,
					// but in this case, we're searching to documentElement, so we
					// have to add it back in.
					if(container === doc && !isBodyStatic
					&& !IS_CONTAINER_BODY_RELATIVE_INCLUDING_HTML_PADDING_REL_CHILD) {
						if(!dcs) dcs = defaultView.getComputedStyle(documentElement,'');
						bodyOffsetTop += parseFloat(dcs.paddingTop)||0;
						bodyOffsetLeft += parseFloat(dcs.paddingLeft)||0;
					}
				}
				else if(IS_BODY_TOP_INHERITED) {
					bodyOffsetTop -= parseFloat(bcs.top);
					bodyOffsetLeft -= parseFloat(bcs.left);
				}
				if(IS_BODY_MARGIN_INHERITED && (!isLastOffsetElementPositioned || container === body)) {
					bodyOffsetTop -= parseFloat(bcs.marginTop)||0;
					bodyOffsetLeft -= parseFloat(bcs.marginLeft)||0;
				}
			}
			el.cumulativeOffsetLeft = Math.round(offsetLeft + bodyOffsetLeft);
			el.cumulativeOffsetTop = Math.round(offsetTop + bodyOffsetTop);
			return returnCoords(el);
		}
	},



	cumulativeOffsetFixedInit: function () {
		inited = true;
	    var body = doc.body;
	    if(!body) return;
	    var marginTop = "marginTop", position = "position", padding = "padding",
	        stat = "static",
	        border = "border", s = body.style,
	        bCssText = s.cssText,
	        bv = '1px solid transparent',
	        z = "0",
	        one = "1px",
	        offsetTop = "offsetTop",
	        ds = documentElement.style,
	        dCssText = ds.cssText,
	        x = doc.createElement('div'),
	        xs = x.style,
	        table = doc.createElement(TABLE);

	    s[padding] = s[marginTop] = s.top = z;
	    ds.position = stat;

	    s[border] = bv;

	    xs.margin = z;
	    xs[position] = stat;

	    // insertBefore - to avoid environment conditions with bottom script
	    // where appendChild would fail.
	    x = body.insertBefore(x, body.firstChild);
	    IS_PARENT_BODY_BORDER_INCLUDED_IN_OFFSET = (x[offsetTop] === 1);

	    s[border] = z;

	    // Table test.
	    table.innerHTML = "<tbody><tr><td>x</td></tr></tbody>";
	    table.style[border] = "7px solid";
	    table.cellSpacing = table.cellPadding = z;

	    body.insertBefore(table, body.firstChild);
	    IS_TABLE_BORDER_INCLUDED_IN_TD_OFFSET = table.getElementsByTagName("td")[0].offsetLeft === 7;

	    body.removeChild(table);

	    // Now add margin to determine if body offsetTop is inherited.
	    s[marginTop] = one;
	    s[position] = relative;
	    IS_BODY_MARGIN_INHERITED = (x[offsetTop] === 1);

	    //IS_BODY_OFFSET_TOP_NO_OFFSETPARENT = body.offsetTop && !body.offsetParent;

	    IS_BODY_OFFSET_EXCLUDING_MARGIN = body[offsetTop] === 0;
	    s[marginTop] = z;
	    s.top = one;
	    IS_BODY_TOP_INHERITED = x[offsetTop] === 1;

	    s.top = z;
	    s[marginTop] = one;
	    s[position] = xs[position] = relative;
	    IS_BODY_OFFSET_IGNORED_WHEN_BODY_RELATIVE_AND_LAST_CHILD_POSITIONED = x[offsetTop] === 0;

	    xs[position] = "absolute";
	    s[position] = stat;
	     if(x.offsetParent === body) {
	        s[border] = bv;
	        xs.top = "2px";
	        // XXX Safari gets offsetParent wrong (says 'body' when body is static,
	        // but then positions element from ICB and then subtracts body's clientWidth.
	        // Safari is half wrong.
	        //
	        // XXX Mozilla says body is offsetParent but does NOT subtract EL's offsetLeft/Top.
	        // Mozilla is completely wrong.
	        IS_STATIC_BODY_OFFSET_PARENT_BUT_ABSOLUTE_CHILD_SUBTRACTS_BODY_BORDER_WIDTH = x[offsetTop] === 1;
	        s[border] = z;

	        xs[position] = relative;
	        ds[padding] = one;
	        s[marginTop] = z;

	        IS_CONTAINER_BODY_STATIC_INCLUDING_HTML_PADDING = x[offsetTop] === 3;

	        // Opera does not respect position: relative on BODY.
	        s[position] = relative;
	        IS_CONTAINER_BODY_RELATIVE_INCLUDING_HTML_PADDING_REL_CHILD = x[offsetTop] === 3;

	        xs[position] = "absolute";
	        IS_CONTAINER_BODY_RELATIVE_INCLUDING_HTML_PADDING_ABS_CHILD = x[offsetTop] === 3;

	        ds[padding] = z;
	        ds[marginTop] = one;

	        // Opera inherits HTML margin when body is relative and child is relative or absolute.
	        IS_CONTAINER_BODY_INCLUDING_HTML_MARGIN = x[offsetTop] === 3;
	    }

	    // xs.position = "fixed";
	    // FIXED_HAS_OFFSETPARENT = x.offsetParent != null;

	    body.removeChild(x);
	    s.cssText = bCssText||"";
	    ds.cssText = dCssText||"";
	}


});