/* adapted from http://www.alistapart.com/articles/alternate/ */

function setActiveStyleSheet(title) {
  var i, a, main;
  for(i=0; (a = document.getElementsByTagName("link")[i]); i++) {
    if(a.getAttribute("rel").indexOf("style") != -1 && a.getAttribute("title")) {
      a.disabled = true;
      if(a.getAttribute("title") == title) a.disabled = false;
    }
  }
}

function getActiveStyleSheet() {
  var i, a;
  for(i=0; (a = document.getElementsByTagName("link")[i]); i++) {
    if(a.getAttribute("rel").indexOf("style") != -1 && a.getAttribute("title") && !a.disabled) return a.getAttribute("title");
  }
  return null;
}

function getPreferredStyleSheet() {
  var i, a;
  for(i=0; (a = document.getElementsByTagName("link")[i]); i++) {
    if(a.getAttribute("rel").indexOf("style") != -1
       && a.getAttribute("rel").indexOf("alt") == -1
       && a.getAttribute("title")
       ) return a.getAttribute("title");
  }
  return null;
}

function createCookie(name,value,days) {
  if (days) {
    var date = new Date();
    date.setTime(date.getTime()+(days*24*60*60*1000));
    var expires = "; expires="+date.toGMTString();
  }
  else expires = "";
  document.cookie = name+"="+value+expires+"; path=/";
}

function readCookie(name) {
  var nameEQ = name + "=";
  var ca = document.cookie.split(';');
  for(var i=0;i < ca.length;i++) {
    var c = ca[i];
    while (c.charAt(0)==' ') c = c.substring(1,c.length);
    if (c.indexOf(nameEQ) == 0) return c.substring(nameEQ.length,c.length);
  }
  return null;
}

function getQueryVariable(variable) 
{  
	var query = window.location.search.substring(1);  
	var vars = query.split("&");  
	for (var i=0;i<vars.length;i++) 
	{    
		var pair = vars[i].split("=");    
		if (pair[0] == variable) 
		{      
		return pair[1];    
		}  
	} 
	return null;
}
function getContrastStyleSheetTitle(num)
{
	// return style sheet based on num (use case switch)
	//return("Hello there Tracey " + num);
	switch (num)
	{
		case "1": 
		return 'high contrast stylesheet';
		break;
		case "3": 
		return 'low contrast stylesheet';
		break;
		default : return 'default colour stylesheet';
	}
}



window.onload = function(e) {
  var cookie = readCookie("style");
  if(getQueryVariable('ss') != null)
  {
	var title = getContrastStyleSheetTitle(getQueryVariable('ss'));
  }
  else
  {
	var title = cookie ? cookie : getPreferredStyleSheet();
  }
  //setActiveStyleSheet('high contrast stylesheet');
  setActiveStyleSheet(title);
}

window.onunload = function(e) {
  var title = getActiveStyleSheet();
  createCookie("style", title, 365);
}

var cookie = readCookie("style");
var title = cookie ? cookie : getPreferredStyleSheet();
//setActiveStyleSheet('high contrast stylesheet');
setActiveStyleSheet(title);