/* Smooth scrolling
	 Changes links that link to other parts of this page to scroll
	 smoothly to those links rather than jump to them directly, which
	 can be a little disorienting.
	 
	 sil, http://www.kryogenix.org/
	 
	 v1.0 2003-11-11
	 v1.1 2005-06-16 wrap it up in an object
*/

var ss = {
	fixAllLinks: function() {
		// Get a list of all links in the page
		var allLinks = document.getElementsByTagName('a');
		// Walk through the list
		for (var i=0;i<allLinks.length;i++) {
			var lnk = allLinks[i];
			if ((lnk.href && lnk.href.indexOf('#') != -1) && 
					( (lnk.pathname == location.pathname) ||
			('/'+lnk.pathname == location.pathname) ) && 
					(lnk.search == location.search)) {
				// If the link is internal to the page (begins in #)
				// then attach the smoothScroll function as an onclick
				// event handler
				ss.addEvent(lnk,'click',ss.smoothScroll);
			}
		}
	},

	smoothScroll: function(e) {
		// This is an event handler; get the clicked on element,
		// in a cross-browser fashion
		if (window.event) {
			target = window.event.srcElement;
		} else if (e) {
			target = e.target;
		} else return;

		// Make sure that the target is an element, not a text node
		// within an element
		if (target.nodeName.toLowerCase() != 'a') {
			target = target.parentNode;
		}

		// Paranoia; check this is an A tag
		if (target.nodeName.toLowerCase() != 'a') return;

		// Find the <a name> tag corresponding to this href
		// First strip off the hash (first character)
		anchor = target.hash.substr(1);
		// Now loop all A tags until we find one with that name
		var allLinks = document.getElementsByTagName('a');
		var destinationLink = null;
		for (var i=0;i<allLinks.length;i++) {
			var lnk = allLinks[i];
			if (lnk.name && (lnk.name == anchor)) {
				destinationLink = lnk;
				break;
			}
		}
		if (!destinationLink) destinationLink = document.getElementById(anchor);

		// If we didn't find a destination, give up and let the browser do
		// its thing
		if (!destinationLink) return true;

		// Find the destination's position
		var destx = destinationLink.offsetLeft; 
		var desty = destinationLink.offsetTop;
		var thisNode = destinationLink;
		while (thisNode.offsetParent && 
					(thisNode.offsetParent != document.body)) {
			thisNode = thisNode.offsetParent;
			destx += thisNode.offsetLeft;
			desty += thisNode.offsetTop;
		}

		// Stop any current scrolling
		clearInterval(ss.INTERVAL);

		cypos = ss.getCurrentYPos();
		height = window.innerHeight || document.documentElement.clientHeight;

		ss.INTERVAL =
setInterval('ss.scrollWindow('+desty+',"'+anchor+'")',10);

		// And stop the actual click happening
		if (window.event) {
			window.event.cancelBubble = true;
			window.event.returnValue = false;
		}
		if (e && e.preventDefault && e.stopPropagation) {
			e.preventDefault();
			e.stopPropagation();
		}
	},

	scrollWindow: function(dest,anchor) {
		wascypos = ss.getCurrentYPos();
		isAbove = (wascypos < dest);
		window.scrollTo(0,wascypos + (dest - wascypos)/ss.STEPS);
		iscypos = ss.getCurrentYPos();
		isAboveNow = (iscypos < dest);
		if ((isAbove != isAboveNow) || (wascypos == iscypos)) {
			// cancel the repeating timer
			clearInterval(ss.INTERVAL);
			// and jump to the link directly so the URL's right
			location.hash = anchor;
		}
	},

	getCurrentYPos: function() {
		if (document.body && document.body.scrollTop)
			return document.body.scrollTop;
		if (document.documentElement && document.documentElement.scrollTop)
			return document.documentElement.scrollTop;
		if (window.pageYOffset)
			return window.pageYOffset;
		return 0;
	},

	addEvent: function(elm, evType, fn, useCapture) {
		// addEvent and removeEvent
		// cross-browser event handling for IE5+,	NS6 and Mozilla
		// By Scott Andrew
		if (elm.addEventListener){
			elm.addEventListener(evType, fn, useCapture);
			return true;
		} else if (elm.attachEvent){
			var r = elm.attachEvent("on"+evType, fn);
			return r;
		} else {
			alert("Handler could not be removed");
		}
	} 
}

ss.STEPS = 15;

ss.addEvent(window,"load",ss.fixAllLinks);