/** Kelkoo Related Products Blog Widget
  * Ben Ward
  * EU Hack Day V
  * 2008-02-08
  */
  
/** In your HTML, you need to put the scriptless fallback HTML, which
  * be enhanced by this script:
  * e.g. 
  <div id="related-products">
      <h3>Related Products</h3>
      <div id="related-results">
          <p>
              Search <a href="http://kelkoo.co.uk">Kelkoo</a>
              to compare prices of products of all shapes and sizes.
          </p>
      </div>
      <p><strong>Powered by <a href="http://kelkoo.co.uk">Kelkoo</a>,
          and <a href="http://microformats.org/">microformats</a>
          </strong></p>
  </div>
  */
 
/** You must then call the init() functionon page load, customise the 
  * ID parameter to correspond to the mark-up you create above.
  * e.g.
  YAHOO.EU.BenWard.HListingProductWidget.init(
      "related-results",
      "http://shopping.kelkoo.co.uk/ctl/do/search?siteSearchQuery=",
      {}
  ); 
  */
  
(function() {
    
    // Load YUI prerequisites into the page
    try {
        if(YAHOO) {};
    }
    catch (e) {
        throw "Need YAHOO core";
    }
    try {
        if(YAHOO.util.Dom) {};
    }
    catch (e) {
        throw "Need YAHOO Dom";
    }
    // Declare namespace
    YAHOO.namespace("YAHOO.EU.BenWard");
        
    // Widget object:
    // Pass an empty DIV element ID into the constructor 
    YAHOO.EU.BenWard.HListingProductWidget = {
        // Some settings
        parser : "http://hack.ben-ward.co.uk/parse/proxy.php?profile=hlisting&output=json&callback=YAHOO.EU.BenWard.HListingProductWidget.callbackListings&url=",
        widget : undefined,
        provider : undefined,
        sourceurl: undefined,
        listings : undefined,
        
        // Initialisation takes an element ID name, provider URL and
        // optional preferences structure.
        init : function(el, provider, options) {
            self = YAHOO.EU.BenWard.HListingProductWidget;
            
            // Get the widget container and confirm its existence
            self.widget = document.getElementById(el);
            if(!self.widget) {
                return false;
                // Here the specified container doesn't exist, so fail 
            }
            
            // Similarly, if no search provider URL is provided, the script fails
            self.provider = provider;
            if(self.provider == undefined || self.provider == '') {
                return false;
            }
            
            // The widget is somewhat configurable, for the number of results to
            // display, for example. Using an object for all options makes this 
            // extensible in a tidy manner.
            if(self.options === undefined) {
                self.options = {};
            }
            self.options.resultsLength = self.options.resultsLength || "5";
            
            // With the widget configured and primed, run the first steps to load the
            // search result data    
            var tags = self.getTags();
            self.queryListings(tags);
        },
        getTags : function() {
            // Get tags (as strings), from each rel-tag microformat on the page
            var tags = [];
            YAHOO.util.Dom.getElementsBy(
                function(anchor) {
                    var rel = anchor.getAttribute('rel');
                    if(rel !== undefined && rel !== null) {
                        return (rel.indexOf("tag") > -1);
                    }
                    else {
                        return false;
                    }
                },
                "a",
                document.body,
                function(a) {
                    // The rel-tag specification states that the tag itself is not
                    // the inner text on the anchor, but is instead the last fragment
                    // of the URL.
                    // See http://microformats.org/wiki/rel-tag
                    var segments = a.href.split('/');
                    var tag = segments[segments.length-1];
                    tags.push(tag);
                }
            );
            return tags;
        },
        queryListings : function(tags) {
            self = YAHOO.EU.BenWard.HListingProductWidget;
            // If there are tags, search for products
            var products;
            if(tags.length > 0) {
                
                // The query is cross-site, so insert a new script element with
                // the webservice URL, and then pass it a callback function
                
                var query = tags.join("%20");
                var qscript = document.createElement("script");
                qscript.type = "text/javascript";
                self.datasource = self.provider + query;

                // self.parser is a string, pre-set as:
                // "http://hack.ben-ward.co.uk/parse/proxy.php?
                // profile=hlisting
                // &output=json
                // &callback=YAHOO.EU.BenWard.HListingProductWidget.callbackListings
                // &url=",

                qscript.src = self.parser + self.datasource;
                var body = document.getElementsByTagName('body')[0];
                body.appendChild(qscript);
            }
        },
        callbackListings : function(listings) {
            var self = YAHOO.EU.BenWard.HListingProductWidget;
            
            self.listings = listings;
            self.renderWidget();            
        },
        renderWidget : function() {
            var self = YAHOO.EU.BenWard.HListingProductWidget;            
            if(self.listings !== undefined && self.listings.length > 0) {            
                // With it verified that there are results to display,
                // replace the entire static content of the ‘widget’ element

                self.widget.innerHTML = "";
                
                // Results are going to be displayed in a list, ordered by
                // popularity (the same order as Kelkoo sends back by default)    
                var list = document.createElement("ol");
                for(
                    var i=0; 
                    (listing = self.listings[i]) 
                     && (i < self.options.resultsLength); 
                    i++
                ) {
                    // For each result (up to the {resultsLength} limit set in the
                    // widget options), create an LI, fill it with content and then
                    // append it to the list.
                    var li = document.createElement("li");

                    var item = document.createElement("a");
                    item.className = "fn";
                    
                    if(listing.item.url !== undefined) {
                        item.href = listing.item.url;
                    }
                    else {
                        // Microformats are flexible to publishers, so handle
                        // situations where a product might not have a URL of its 
                        // own, and instead link back to the datasource that the
                        // results were parsed from.    
                        item.href = self.datasource;
                    }
                    
                    var lister = document.createElement("span");
                    lister.className = "lister";
                    var price = document.createElement("span");
                    price.className = "price";
                    
                    item.appendChild(document.createTextNode(listing.item.fn));
                    lister.appendChild(document.createTextNode(listing.lister.fn));
                    price.appendChild(document.createTextNode(listing.price));
                    
                    li.appendChild(item);
                    li.appendChild(lister);
                    li.appendChild(price);

                    list.appendChild(li);                    
                }
                // Finally, append the list to the now empty widget container element.    
                self.widget.appendChild(list);
            }
        }
    };
})();