var W3CDOM = (document.getElementsByTagName && document.createElement);

// When used from within exhibition.js, exhibition.js should be doing the onload
// setup

if (W3CDOM)
	document.write('<link rel="stylesheet" href="env08-menu.css" />');
// When used via exhibition.js, exhibition.js should handling onloads
window.onload = function () {
	if (W3CDOM) {
	  rollup();
	}
}
window.onload=rollup;

function rollout(objMenuitem, objEvent)
{
    var iKeyCode;

    // Check if from a keyboard - non IE, but
    // irrelevant as tab doesn't trigger the 
    // keypress event in IE
    if (objEvent && objEvent.type == 'keypress')
    {
        if (objEvent.keyCode)
            iKeyCode = objEvent.keyCode;
        else if (objEvent.which)
            iKeyCode = objEvent.which;

        // If it's not the enter key or space key, 
        // pass control back to the browser
        if (iKeyCode != 13 && iKeyCode != 32)
            return true;
    }

    // Work out what we need to do
    if (objMenuitem.nextSibling.style.display == 'block')
        var strDisplay = 'none'
    else
        var strDisplay = 'block';

    // Close any nested lists that are open
    var objMenu = document.getElementById('mainnav');
    var objNested = objMenu.getElementsByTagName('ul');

    for (var i=0; i<objNested.length; i++)
        if (objNested[i].style.display == 'block')
            objNested[i].style.display = 'none';

    objMenuitem.nextSibling.style.display = strDisplay;
    
    // Keep any parent menus for this item open
    while (objMenuitem.parentNode.parentNode.id != 'mainnav')
    {
        objMenuitem = objMenuitem.parentNode.parentNode;
        objMenuitem.style.display = 'block';
    }

    // Stop the browser requesting the link
    return false;
}

function rollup()
{
    var bRollup, objLinks, objNode, objAnchor;

    // Check we're working with a DOM compliant browser
    if (document.getElementById && document.createElement)
    {
        var strLocation = window.location;

        var objMenu = document.getElementById('mainnav');

        var objNested = objMenu.getElementsByTagName('ul');

        // Hide each of the nested unordered list
        for (var i=0; i<objNested.length; i++)
        {
            objLinks = objNested[i].getElementsByTagName('a');
            
            // Only hide, if the current location is not found in the list
            bRollup = true;

            for (var j=0; j<objLinks.length; j++)
            {
              if (objLinks[j].href == strLocation)
              {                     
                bRollup = false;
                keep_node_open(objLinks[j],strLocation);
              }
            }
            
            // If the firstChild of the ul is a link and is the currentpage
            // don't roll it up 
            
            // find parent <li> element
            var parent_node = objNested[i].parentNode;
            while (parent_node != undefined && 
                   parent_node.nodeName.toLowerCase() != 'li') {
              parent_node = parent_node.parentNode; 
            }
            
            // See if we can find a link as an immediate child
            var nodeWithLink = null;
            if (parent_node != undefined) {
              nodeWithLink = parent_node.firstChild;
            }
            while ( nodeWithLink != undefined && 'a' != nodeWithLink.nodeName.toLowerCase() ) {
              if (nodeWithLink.nextSibling) {
                nodeWithLink = nodeWithLink.nextSibling;
              }
              else {
                nodeWithLink = null;
              }
            }
            
            bIntroPage = false;
            if (nodeWithLink) {
              bIntroPage = true;
              if (nodeWithLink.href == strLocation)
              {                     
                bRollup = false;
                keep_node_open(nodeWithLink,strLocation);
              }
            }
            
            if (bRollup == true)
                objNested[i].style.display = 'none';
            else
                objNested[i].style.display = 'block';

            // The top-level is a real page which is a link already
            if (bIntroPage)
              continue;
              
            // Place the top-level text in an anchor tag
            objNode = objNested[i].parentNode;
            strContent = objNode.firstChild.data;
                        
            objAnchor = document.createElement('a');
            objAnchor.href = '#';
            objAnchor.onclick = function(event){return rollout(this, event);}
            objAnchor.onkeypress = function(event){return rollout(this, event);}
            objAnchor.appendChild(document.createTextNode(strContent));

            objNode.replaceChild(objAnchor, objNode.firstChild);
        }

        // Keep any parent menus for the current item
        if (document.getElementById('jsKeepOpen'))
        {
            var objKeepOpen = document.getElementById('jsKeepOpen');
            while (objKeepOpen.parentNode.id != 'mainnav')
            {
                objKeepOpen = objKeepOpen.parentNode;
                if (objKeepOpen.className != 'hidden')  {
                  objKeepOpen.style.display = 'block';
                }
            }
        }
    }
}

function keep_node_open(aNode,strLocation) {  
  // Added by John Hunter  
  // remove link for current page

  aNode.id = 'jsKeepOpen';
  // RT 2007-03-30, RJ doesn't need
  // objNode = aNode;
  // strContent = objNode.firstChild.data;
  // var objCurrentPage = document.createElement('normal');
  // objCurrentPage.appendChild(document.createTextNode(strContent));
  // objNode.parentNode.replaceChild(objCurrentPage, objNode);
  
  // // Add an id so we can keep the parents open
  // objCurrentPage.id = 'jsKeepOpen';
}