// Copied from http://www.sitepoint.com/article/scroll-smoothly-javascript

function ss_fixAllLinks() {
  var allLinks = document.getElementsByTagName('a');
  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)) {
      ss_addEvent(lnk, 'click', smoothScroll);
    }
  }
}

function smoothScroll(e) {
  if (window.event) {
    target = window.event.srcElement;
  } else if (e) {
    target = e.target;
  } else return;
  if (target.nodeType == 3) { 
    target = target.parentNode;
  }
  if (target.nodeName.toLowerCase() != 'a') return;
  anchor = target.hash.substr(1);
  var destinationLink = document.getElementById(anchor);
  if (!destinationLink) return true;
  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;
  }
  clearInterval(ss_INTERVAL);
  cypos = ss_getCurrentYPos();
  ss_stepsize = parseInt((desty - cypos) / ss_STEPS);
  ss_INTERVAL = setInterval('ss_scrollWindow(' + ss_stepsize + ', ' + desty + ', "' + anchor + '")', 10);
  if (window.event) {
    window.event.cancelBubble = true;
    window.event.returnValue = false;
  }
  if (e && e.preventDefault && e.stopPropagation) {
    e.preventDefault();
    e.stopPropagation();
  }
}

function ss_scrollWindow(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)) {
    window.scrollTo(0, dest);
    clearInterval(ss_INTERVAL);
    //location.hash = anchor;
  }
}

function ss_getCurrentYPos() {
  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;
}

function ss_addEvent(elm, evType, fn, useCapture) {
  // 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;
  }
}

var ss_INTERVAL;
var ss_STEPS = 25;

ss_addEvent(window,'load',ss_fixAllLinks);