var http_request = false;
   var link;
   var linkInnerText;
   var linkURL;

   function makePOSTRequest(url, parameters) {
      http_request = false;
      if (window.XMLHttpRequest) { // Mozilla, Safari,...
         http_request = new XMLHttpRequest();
         if (http_request.overrideMimeType) {
         	// set type accordingly to anticipated content type
            http_request.overrideMimeType('text/xml');
            //http_request.overrideMimeType('text/html');
         }
      } else if (window.ActiveXObject) { // IE
         try {
            http_request = new ActiveXObject("Msxml2.XMLHTTP");
         } catch (e) {
            try {
               http_request = new ActiveXObject("Microsoft.XMLHTTP");
            } catch (e) {}
         }
      }
      if (!http_request) {
         alert('Cannot create XMLHTTP instance');
         return false;
      }
      
      http_request.onreadystatechange = alertContents;
      http_request.open('POST', url, true);
      http_request.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
      http_request.setRequestHeader("Content-length", parameters.length);
      http_request.setRequestHeader("Connection", "close");
      http_request.send(parameters);
   }

   function alertContents() {
      if (http_request.readyState == 4) {
         if (http_request.status == 200) {
            //alert(http_request.responseText);
            if ( this.responseXML.documentElement.tagName != 'error' ) {
                link.innerHTML = linkInnerHTML;
                link.href = linkURL;
            }
            else {
              alert('There was a problem with the request.');
            }
         } else {
            //alert('There was a problem with the request.');
         }
      }
   }
   
   function add_to_catalog(asin, locale, index) {
     var poststr = "format=xml&action=add&asin=" + asin + "&locale=" + locale + "&index=" + index;
     link = document.getElementById( asin );
     linkInnerHTML = 'Remove from Catalog';
     linkURL = 'javascript:remove_from_catalog(\'' + asin + '\', \'' + locale + '\', \'' + index + '\');';
     makePOSTRequest( '/catalog.php', poststr );
   }
   
   function remove_from_catalog(asin, locale, index) {
     var poststr = "format=xml&action=remove&asin=" + asin + "&locale=" + locale + "&index=" + index;
     link = document.getElementById( asin );
     linkInnerHTML = 'Add to Catalog';
     linkURL = 'javascript:add_to_catalog(\'' + asin + '\', \'' + locale + '\', \'' + index + '\');';
     makePOSTRequest( '/catalog.php', poststr );
   }

   function add_to_wishlist(asin, locale, index) {
     var poststr = "format=xml&action=add&asin=" + asin + "&locale=" + locale + "&index=" + index;
     link = document.getElementById( asin + '_wish' );
     linkInnerHTML = 'Remove from Wishlist';
     linkURL = 'javascript:remove_from_wishlist(\'' + asin + '\', \'' + locale + '\', \'' + index + '\');';
     makePOSTRequest( '/wishlist.php', poststr );
   }
   
   function remove_from_wishlist(asin, locale, index) {
     var poststr = "format=xml&action=remove&asin=" + asin + "&locale=" + locale + "&index=" + index;
     link = document.getElementById( asin  + '_wish' );
     linkInnerHTML = 'Add to Wishlist';
     linkURL = 'javascript:add_to_wishlist(\'' + asin + '\', \'' + locale + '\', \'' + index + '\');';
     makePOSTRequest( '/wishlist.php', poststr );
   }