/* Constants */
var AXIS_X = 0;
var AXIS_Y = 1;


/*Shortcut to getElementById*/
function grabId(elementId) {
    var object = document.getElementById(elementId);
    return object;

}


/* Another shortcut to getElementById */
function getNode(node) {
	return document.getElementById(node);
}


/* Destroy a node with the Death Star */
function killNode(nodeID) {
	var node = getNode(nodeID);
	var nodeParent = node.parentElement;
	if (typeof nodeParent != "undefined") {
		nodeParent.removeChild(node);
	} else {
		node.style.display = "none";
	}
}


/* Replace text in a node. */
function swapTextNode(parentObject, newText) {
    parentObject.replaceChild(document.createTextNode(newText), parentObject.firstChild);
}


/* Replace text in a node. Has more protection than the previous version and will fall back on non-DOM techniques if it can't pick out the childNodes */
function replaceInnerText(node, text) {
	//	replacement for node.innerHTML = text; which is apparently broken in Safari 1.2.4
	if (typeof node.childNodes != "undefined" && node.childNodes.length > 0) {
		var newnode = document.createTextNode(text);
		node.replaceChild(newnode, node.firstChild);
	} else {
		// fall back on the old school just in case
		node.innerHTML = text;
	}
}


/* Cross browser solution to DOM getComputedStyle() (Safari doesn't currently support this) */
function grabComputedStyle(elementObject) {

    if (document.defaultView && document.defaultView.getComputedStyle ) {
        return  document.defaultView.getComputedStyle(elementObject, null);
     } else if  (elementObject.currentStyle) {
        return elementObject.currentStyle;
    } else  {
        return null;
    }

}


/* Return the target node for an event. */
function getEventTarget(evt) {
	var tgt = evt.srcElement;
	if (!tgt)
		tgt = evt.target;
	return tgt;
}


/* Clear out any text that may have been selected (called "ranges") by dragging the mouse mid-click. */
function clearRanges(event) {
	if (isMacIE) { // Mac IE is blowing up
	} else if (document.selection) { // IE 6
		document.selection.empty();
	} else if (window.getSelection()) { // NS 6
		window.getSelection().removeAllRanges();
	} else { // Safari, etc.
		event.stopPropagation();
	}
}


/* How much the document's been scrolled vertically. Needed for correcting position calculations. */
function getDocumentScrollAmount() {
	if (!isSafari) {
		return document.body.scrollTop;
	} else {
		return 0;
	}
}


/* Computes the total vertical offset of a node, the sum of the enclosing objects' vertical offset. */
function getElementOffsetY(element) {
	var totalOffset = 0;
	if (element.offsetTop != null) {
        totalOffset += element.offsetTop;
		while (element.offsetParent) {
			totalOffset += element.offsetParent.offsetTop;
			element = element.offsetParent;
		}
	}
	return totalOffset;
}

/* Computes the total horizontal offset of a node, the sum of the enclosing objects' horizontal offset. */
function getElementOffsetX(element) {
    var totalOffset = 0;
    if (element.offsetLeft != null) {
        totalOffset += element.offsetLeft;
        while (element.offsetParent) {
            totalOffset += element.offsetParent.offsetLeft;
            element = element.offsetParent;
        }
    }
    return totalOffset;
}

/* Gets the position of the top of a node. */
function getNodeTop(nodeId) {
	var itemOver = document.getElementById(nodeId);
	var itemOverTop = itemOver.style.top ? (itemOver.offsetTop - stripUnits(itemOver.style.top)) : itemOver.offsetTop;
	return itemOverTop;
}


/* Moves an object vertically. Pass in either the node or the node's ID. If amount is positive, move it down. Negative? Move it up. */
function moveNode(mover, amount) {
	if (typeof mover == "string")
		mover = getNode(mover);
	
	if (mover.style.top) {
		mover.style.top = stripUnits(mover.style.top) + amount + "px";
	} else {
		mover.style.top = (amount) + "px";
	}
}

/* Debug utility; displays all of the properties of an object in a popup */
function displayObject(obj) {
	var msg = "";
	for (var prop in obj) {
		msg += prop;
		msg += ": ";
		msg += prop.value;
		msg += "\n";
	}
	window.alert(msg);
}