// 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) {
    // 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();
        }
    }
    else {
        clearTopicList();
    }
}

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

// invoked by "Category" select element change;
// loads chosen XML document, clears Topics select
// element, loads new items into Topics select element
function loadDoc(evt) {
    // equalize W3C/IE event models to get event object
    evt = (evt) ? evt : ((window.event) ? window.event : null);
    if (evt) {
        // equalize W3C/IE models to get event target reference
        var elem = (evt.target) ? evt.target : ((evt.srcElement) ? evt.srcElement : null);
        if (elem) {
            try {
                //we don't actually care if the index is 0
                //if (elem.selectedIndex > 0) {
                    loadXMLDoc("proxy/shelterList.cgi?state=" + elem.options[elem.selectedIndex].value);
                //}	
            }
            catch(e) {
                //var msg = (typeof e == "string") ? e : ((e.message) ? e.message : "Unknown Error");
                //alert("Unable to get XML data:\n" + msg);
                clearTopicList();
                return;
            }
        }
    }
}



// empty Topics select list content
function clearTopicList() {
    var select = document.getElementById("topics");
    select.innerHTML = '';
}


// fill Topics select list with items from
// the current XML document
function buildTopicList() { 
    var select = document.getElementById("topics");
    var items = req.responseXML.getElementsByTagName("item");
    // loop through <item> elements, and add each nested
    // <title> element to Topics select element
    //set initial entry 

	var div_text;
    if(items.length > 0) {
	    div_text = "<ul>";
	    for (var i = 0; i < items.length; i++) {
	        shelter_name = getElementTextNS("", "name", items[i], 0);
	        shelter_id = getElementTextNS("", "id", items[i], 0);
	        pilot = getElementTextNS("", "pilot", items[i], 0);
	        div_text += "<li><a href=\"http://www.petfinder.com/pet-search?shelter_id=" + shelter_id + "\">" + shelter_name + "</a>";
	        if(pilot > 0) {
	            div_text += "&nbsp;*";
	        }
	        div_text += "</li>";
	    }
	    div_text += "</ul>";
	}
	else {
		div_text = "No organizations are participating in the Sponsor a Pet program from this state.  Please check back later, as more organizations are joining every day.";
	}
    select.innerHTML = div_text;
}

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 (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 "n/a";
    }
}