/* 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 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);