// global flag
var isIE = false;
// global request and XML document objects
var req;

// retrieve XML document (reusable generic function);
// parameter is URL string (relative or complete) to
// an .xml file whose Content-Type is a valid XML
// type, such as text/xml; XML source must be from
// same domain as HTML file
function loadXMLDoc(url, fallbackurl) {
    dt = new Date();
    url += '&time=' + ((dt.getTime() - dt.getMilliseconds()) / 1000);
    // branch for native XMLHttpRequest object
    if (window.XMLHttpRequest) {
        req = new XMLHttpRequest();
        req.onreadystatechange = processReqChange;
        req.open("GET", url, true);
        req.send(null);
        // branch for IE/Windows ActiveX version
    } else if (window.ActiveXObject) {
        isIE = true;
        req = new ActiveXObject("Microsoft.XMLHTTP");
        if (req) {
            req.onreadystatechange = processReqChange;
            req.open("GET", url, true);
            req.send();
        }
    }
    if(!req && fallbackurl){
        // fall back 
            location.replace(fallbackurl);
    }
}


// handle onreadystatechange event of req object
function processReqChange() {
    // only if req shows "loaded"
    if (req.readyState == 4) {
        // only if "OK"
        if (req.status == 200) {
            loadDiv("itemavailability", "content", "encoded");
        } else {
            location.replace(fallbackurl);
            // alert("There was a problem retrieving the XML data:\n" + req.statusText);
        }
    }
}

// retrieve text of an XML document element, including
// elements using namespaces
function getElementTextNS(prefix, local, parentElem, index) {
    var result = "";
    if (prefix && isIE) {
        // IE/Windows way of handling namespaces
        result = parentElem.getElementsByTagName(prefix + ":" + local)[index];
    } else {
        // the namespace versions of this method 
        // (getElementsByTagNameNS()) operate
        // differently in Safari and Mozilla, but both
        // return value with just local name, provided 
        // there aren't conflicts with non-namespace element
        // names
        result = parentElem.getElementsByTagName(local)[index];
        // if the Non-IE version didn't work, try the IE version
        if (result == null) {
            result = parentElem.getElementsByTagName(prefix + ":" + local)[index];
        }
    }
    if (result) {
        // get text, accounting for possible
        // whitespace (carriage return) text nodes 
        if (result.childNodes.length > 1) {
            return result.childNodes[1].nodeValue;
        } else {
            return result.firstChild.nodeValue;    
        }
    } else {
        return "Status Unavailable";
    }
}

// load item availability information into correct <div> tag
function loadDiv(divid, prefix, local) {
    var div, content, item;
    item = req.responseXML.getElementsByTagName("item")[0];
    content = getElementTextNS(prefix, local, item, 0);
    div = document.getElementById(divid);
    div.innerHTML = "";
    div.innerHTML = content;
}