var currMenu  = null;
var hdrHeight = 0;
var ftrHeight = 0;
var mainWidth = 0;
var menuURL   = 'menubar.html';
var browser   = navigator.appName;

function showMenu(menuId) {
  hideCurrMenu();
  currMenu = elem(menuId);

  if(currMenu) {
    currMenu.style.display = "block";
  }
}

function hideCurrMenu() {
  if( currMenu ) {
    currMenu.style.display = "none";
    currMenu = null;
  }
}

function toggleElem(elemId) {
  var disp = elem(elemId).style.display;
  if( disp == 'block' ) {
    elem(elemId).style.display = 'none';
  } else {
    elem(elemId).style.display = 'block';
  }
}

function loadXML(url) {
  var xmlhttp = new XMLHttpRequest();
  xmlhttp.open("GET", url, false);
  xmlhttp.send('');
  return xmlhttp.responseXML;
}

function loadText(url) {
  var xmlhttp = new XMLHttpRequest();
  xmlhttp.open("GET", url, false);
  xmlhttp.send('');
  return xmlhttp.responseText;
}

function clearElem(elem) {
  var n=elem.childNodes.length;
  var i=n-1;
  while(i>0) {
    if( elem.childNodes[i].nodeType == 1 ) {
      elem.removeChild(elem.childNodes[i]);
      --n;
    }
    --i;
  }
}


function elem(elemId) {
  return document.getElementById(elemId);
}

function setElementHeight(elemId,height) {
  elem(elemId).style.height = height;
}

function setElementWidth(elemId,width) {
  elem(elemId).style.width = width;
}

function getElementHeight(elemId) {
  return elem(elemId).offsetHeight;
}

function getElementWidth(elemId) {
  return elem(elemId).offsetWidth;
}

function loadMenu() 
{
  elem('menuframe').innerHTML = loadText(menuURL);

  var width = getElementWidth('menubar');  
  var pos   = (mainWidth-width)/2;
  elem('menubar').style.left = pos;
  elem('menubar').style.top  = hdrHeight-27;

  if( browser == "Microsoft Internet Explorer" ) {
	elem('#courses').style.position = 'absolute';
	elem('#courses').style.top = 20;
  }
}

function setHome() 
{
  elem('body').style.display = 'block';
  elem('body').innerHTML = loadText('main.html');
}

function setBody(url) 
{
  elem('body').style.display = 'block';
  elem('body').innerHTML = loadText(url+'?nocache=' + new Date().getTime());
}

function changeContent(contentId) 
{
  var content = elem('content').getElementsByTagName("div");
  for(i=0;i<content.length;++i) {
    content[i].style.display="none";
  }
  elem(contentId).style.display="block";
}

function loadSite() 
{
  if( browser == "Microsoft Internet Explorer" ) {
	elem('main').style.position = 'absolute';
  }

  hdrHeight = getElementHeight('header') + getElementHeight('menuframe');
  ftrHeight = getElementHeight('footer');  
  mainWidth = getElementWidth('main');

  setHome();
  loadMenu();
}  


// function loadMain(name) {
//   var xmlDoc = loadXML(name+".xml");
//   var xslDoc = loadXML(name+".xsl");
//   var images = xmlDoc.getElementsByTagName("image");
//   var index  = Math.round(Math.random()*(images.length-1));
  
//   var xslt = new XSLTProcessor();
//   xslt.importStylesheet(xslDoc);

//   var main = xslt.transformToFragment(images[index],document);
//   var body = document.getElementById("body");
//   clear(body);
//   body.appendChild();
// }