/* 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();
  
	ss_stepsize = parseInt((desty-cypos)/ss.STEPS);
	ss.INTERVAL =
setInterval('ss.scrollWindow('+ss_stepsize+','+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(scramount,dest,anchor) {
	wascypos = ss.getCurrentYPos();
	isAbove = (wascypos < dest);
	window.scrollTo(0,wascypos + scramount);
	iscypos = ss.getCurrentYPos();
	isAboveNow = (iscypos < dest);
	if ((isAbove != isAboveNow) || (wascypos == iscypos)) {
	  // if we've just scrolled past the destination, or
	  // we haven't moved from the last scroll (i.e., we're at the
	  // bottom of the page) then scroll exactly to the link
	  window.scrollTo(0,dest);
	  // 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 = 25;

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