/* allow multiple onload events to take place
 * see http://simonwillison.net/2004/May/26/addLoadEvent/
 */

function addLoadEvent(func) {
  var oldonload = window.onload;
  if (typeof window.onload != 'function') {
    window.onload = func;
  } else {
    window.onload = function() {
      if (oldonload) {
        oldonload();
      }
      func();
    }
  }
}

addLoadEvent(prepDescriptionDisplay);

/*  Enable IE's use of the getElementsByClassName function:
 *  Developed by Robert Nyman, http://www.robertnyman.com
 *  Code/licensing: http://code.google.com/p/getelementsbyclassname/
 */

var getElementsByClassName = function (className, tag, elm){
	if (document.getElementsByClassName) {
		getElementsByClassName = function (className, tag, elm) {
			elm = elm || document;
			var elements = elm.getElementsByClassName(className),
				nodeName = (tag)? new RegExp("\\b" + tag + "\\b", "i") : null,
				returnElements = [],
				current;
			for(var i=0, il=elements.length; i<il; i+=1){
				current = elements[i];
				if(!nodeName || nodeName.test(current.nodeName)) {
					returnElements.push(current);
				}
			}
			return returnElements;
		};
	}
	else if (document.evaluate) {
		getElementsByClassName = function (className, tag, elm) {
			tag = tag || "*";
			elm = elm || document;
			var classes = className.split(" "),
				classesToCheck = "",
				xhtmlNamespace = "http://www.w3.org/1999/xhtml",
				namespaceResolver = (document.documentElement.namespaceURI === xhtmlNamespace)? xhtmlNamespace : null,
				returnElements = [],
				elements,
				node;
			for(var j=0, jl=classes.length; j<jl; j+=1){
				classesToCheck += "[contains(concat(' ', @class, ' '), ' " + classes[j] + " ')]";
			}
			try	{
				elements = document.evaluate(".//" + tag + classesToCheck, elm, namespaceResolver, 0, null);
			}
			catch (e) {
				elements = document.evaluate(".//" + tag + classesToCheck, elm, null, 0, null);
			}
			while ((node = elements.iterateNext())) {
				returnElements.push(node);
			}
			return returnElements;
		};
	}
	else {
		getElementsByClassName = function (className, tag, elm) {
			tag = tag || "*";
			elm = elm || document;
			var classes = className.split(" "),
				classesToCheck = [],
				elements = (tag === "*" && elm.all)? elm.all : elm.getElementsByTagName(tag),
				current,
				returnElements = [],
				match;
			for(var k=0, kl=classes.length; k<kl; k+=1){
				classesToCheck.push(new RegExp("(^|\\s)" + classes[k] + "(\\s|$)"));
			}
			for(var l=0, ll=elements.length; l<ll; l+=1){
				current = elements[l];
				match = false;
				for(var m=0, ml=classesToCheck.length; m<ml; m+=1){
					match = classesToCheck[m].test(current.className);
					if (!match) {
						break;
					}
				}
				if (match) {
					returnElements.push(current);
				}
			}
			return returnElements;
		};
	}
	return getElementsByClassName(className, tag, elm);
};

/* unobtrusively add onmouseover handlers to the nav's anchors
 * see http://www.alistapart.com/articles/behavioralseparation
 *
 * 1. check to see that browser supports the functions
 * 2. get the 'nav' div from the page
 * 3. grab all of the 'nav' div's anchors
 * 4. add event handlers to each anchor
 *
 */
function prepDescriptionDisplay() {
    if (document.getElementById &&
        document.getElementsByTagName &&
        getElementsByClassName) {
        if (document.getElementById('nav')) { //
            var nav   = document.getElementById('nav');
            var links = nav.getElementsByTagName('a');

            for (var i = 0; i < links.length; i++) {
                links[i].onmouseover = function() {
                    return displayDescription(this);
                }
            }
        }
        }

}

// switch out which division is appearing on screen
function displayDescription(callingAnchor) {
    var divs = getElementsByClassName('displayed');
    divs[0].className = 'hidden';

    descriptionDiv = document.getElementById('desc-' + callingAnchor.id);
    descriptionDiv.className = 'displayed';
}