/**
 * Wrapper for Ajax calls. Provides flood control. 
 */
cambrient.Ajax = function() {
   var REQUEST_PERIOD_MS = 100;           // How often to make ajax requests
   var MAX_SIMULTANEOUS_REQUESTS = 5;     // Maximum simultaenous ajax requests (remember that comet uses up 1)
   
   var self;                              // pointer to instance of this class
   var recentRequests = new Array();
   var requestQueue = new Array();
   var simultaneousRequests = 0;

   function constructorFn() {
      self = this;
      self.processRequests();
   }

   // Make ajax request   
   constructorFn.prototype.processRequests = function() {
       setTimeout(self.processRequests, REQUEST_PERIOD_MS);
       
       if (simultaneousRequests >= MAX_SIMULTANEOUS_REQUESTS) return;
       if (requestQueue.length == 0) return;
       
       var requestObj = requestQueue.shift();
       if (requestObj.successFunction == null) {
          requestObj.successFunction = function(reply) {
               if (element != null) {
                  element.innerHTML = reply.responseText;
               } else {
                  cambrient[elementId] = reply.responseText;
               }
               
               if (requestObj.chainFunction != null && isFunction(requestObj.chainFunction)) {
                  requestObj.chainFunction.call(reply);
               }
            }
       }

       if (requestObj.errorFunction == null) {
         requestObj.errorFunction = function(reply) {
            cambrient.userMessaging.error('ERROR!! ' + reply);
         }
       }
   
       simultaneousRequests++; 
       if (requestObj.post) {
           new Ajax.Request(cambrient.contextPath + requestObj.url,  {
        	   method: "post",
        	   parameters: requestObj.dataObj,        	   
               onSuccess: function(reply) {
                  cambrient.sessionManager.serverPing(); // reset the session manager
                  simultaneousRequests--;
                  requestObj.successFunction(reply);
               },
               onFailure: function(reply) {
                  simultaneousRequests--;
                  requestObj.errorFunction(reply);
               }
          });
       } else {
           new Ajax.Request(cambrient.contextPath + requestObj.url,  {
               onSuccess: function(reply) {
                  cambrient.sessionManager.serverPing(); // reset the session manager
                  simultaneousRequests--;
                  requestObj.successFunction(reply);
               },
               onFailure: function(reply) {
                  simultaneousRequests--;
                  requestObj.errorFunction(reply);
               }
          });
       }
   }

   // provides flood control by checking if the url was recently requested
   constructorFn.prototype.recentlyRequested = function(url) {
      var idx = requestQueue.find(function(item) {
         if (item.url == url) return true;
         else return false;
      });
      
      if (idx >= 0) {
         return true;
      }
      
      return false;
   } 
   
   // Make ajax request using the POST method   
   constructorFn.prototype.requestPost = function(url, dataObj, successFunction, errorFunction, chainFunction) {
      if (!self.recentlyRequested(url)) {
         requestQueue.push({
            "url": url,
            "post": true,
            "dataObj": dataObj,
            "successFunction": successFunction,
            "errorFunction": errorFunction,
            "chainFunction": chainFunction
         });
      }
   }   
   
   // Make ajax request   
   constructorFn.prototype.request = function(url, successFunction, errorFunction, chainFunction) {
      if (!self.recentlyRequested(url)) {
         requestQueue.push({
            "url": url,
            "successFunction" : successFunction,
            "errorFunction" : errorFunction,
            "chainFunction" : chainFunction
         });
      }
   }
   
   return new constructorFn();
}

cambrient.ajax = new cambrient.Ajax();