///////////////////////////////////////////////////////////////////////////////

// The FeedUpdateBroker class implements a simple RSS fetcher and parser.

// Adapted from WRTKit RssReader example

// Constructor.

function FeedUpdateBroker() {

    this.httpReq = null;

    this.feedAddress = null;

    this.callback = null;

	this.ignoreContent = false;

	this.cancelled = false;

	this.responseParser = this.handleRssResponse;

	this.startFromItem = 0;

	this.maxItems = 0;

}

// Fetches a feed from the specified URL and calls the callback when the feed

// has been fetched and parsed, or if the process results in an error.

FeedUpdateBroker.prototype.doFetchFeed = function(){    

    // create new XML HTTP request

    this.httpReq = new Ajax();

    // set callback

    var self = this;

    this.httpReq.onreadystatechange = function() { self.readyStateChanged(); };

    // initiate the request

    this.httpReq.open("GET", nocache(this.feedAddress), true);

    this.httpReq.send(null);

}

// has been fetched and parsed, or if the process results in an error.

FeedUpdateBroker.prototype.fetchFeed = function(feedURL, callback) {

    // remember callback

    this.callback = callback;

    this.feedAddress = feedURL;

	this.doFetchFeed();

}

// Callback for ready-state change events in the XML HTTP request.

FeedUpdateBroker.prototype.readyStateChanged = function() {

    // complete request?

    if (this.httpReq.readyState == 4) {

        // attempt to get response status

        var responseStatus = null;

        try {

            responseStatus = this.httpReq.status;

        } catch (noStatusException) {}

		// are we being prompted for login?

		var text = this.httpReq.responseText;

		if ( isLoginPrompt (text) ) {

			var self = this;

			login(function(){self.doFetchFeed();});

			return;

		}

        // handle the response and call the registered callback object

		var response = this.httpReq.responseXML;

		if (response == null) {

			// if the content type is not set correctly, we get the response as text

			var xmlparser = new DOMParser();

		    response = xmlparser.parseFromString(this.httpReq.responseText, "text/xml");

		}

        this.callback.feedUpdateCompleted(this.handleResponse(responseStatus, response));

    }

}

// Handles a completed response.

FeedUpdateBroker.prototype.handleResponse = function(responseStatus, xmlDoc){

	if (this.responseParser == null) {

		return this.handleRssResponse(responseStatus, xmlDoc);

	}

	else {

		return this.responseParser.call(this, this, responseStatus, xmlDoc);

	}	

}

FeedUpdateBroker.prototype.handleRssResponse = function(broker, responseStatus, xmlDoc){

	if ( this.cancelled ) {

        return { status: "cancelled" };

	}

    if (responseStatus == 200 && xmlDoc != null) {

        // node ref for iterating

        var node;

        // get last modified time - default to current time

        var lastModified = new Date().getTime();

        var channelElements = xmlDoc.getElementsByTagName("channel");

        if (channelElements.length > 0) {

            node = channelElements[0].firstChild;

            while (node != null) {

                if (node.nodeType == Node.ELEMENT_NODE) {

                    if (node.nodeName == "pubDate" ||

                            node.nodeName == "lastBuildDate" ||

                            node.nodeName == "dc:date") {

                        lastModified = getTextOfNode(node);

                        break;

                    }

                }

                node = node.nextSibling;

            }

        }

        // init feed items array

        var items = [];

        // we got the feed XML so now we'll parse it

        var itemElements = xmlDoc.getElementsByTagName("item");

        for (var i = this.startFromItem; i < itemElements.length; i++) {

			if ( this.maxItems > 0 && this.maxItems < i ) {

				break;

			}

            // iterate through child nodes of this item and gather

            // all the data we need for a feed item

            var title = null;

            var date = null;

            var description = null;

            var url = null;

            var author = null;

            node = itemElements[i].firstChild;

            while (node != null) {

                if (node.nodeType == Node.ELEMENT_NODE) {

                    if (node.nodeName == "title") {

                        // item title

                        title = getTextOfNode(node);

                    } else if (node.nodeName == "pubDate" || node.nodeName == "dc:date") {

                        // item publishing date

                        date = getTextOfNode(node);

                    } else if (node.nodeName == "description" && !this.ignoreContent ) {

                        // item description

                        description = getTextOfNode(node);

                    } else if (node.nodeName == "link") {

                        // link URL

                        url = getTextOfNode(node);

                    } else if (node.nodeName == "dc:creator" ) {

						author = getTextOfNode(node);

					}

                }

                node = node.nextSibling;

            }

            // create the item and add to the items array

            items.push({ title: title, date: date, description: description, url: url, author: author });

        }

        // update was completed successfully

        return { status: "ok", lastModified: lastModified, items: items };

    } else {

        // update failed

        return { status: "error" };

    }

}

// Returns the text of a node.

function getTextOfNode(node) {

    var buf = "";

	// iterate through all child elements and collect all text to the buffer

	var child = node.firstChild;

	while (child != null) {

		if (child.nodeType == Node.TEXT_NODE || child.nodeType == Node.CDATA_SECTION_NODE) {

			// append text to buffer

			if (buf != "") {

				buf += " ";

			}

		}

		child = child.nextSibling;

	}

	return buf;

}

FeedUpdateBroker.prototype.cancel = function() {

	this.cancelled = true;

	this.httpReq.abort();

}