class Resource {
 DataGenerator generator;
 Function beforeRequestCallback;

 Future handleSyncRequest (Map data) {
   num watchID = startWatch('${data["action"]}, ${data['collection']}');

   var action = data["action"];
   var reqVersion = data['version'];
   List<String> modifications = ['add', 'change', 'remove'];

   Future beforeRequest = new Future.value(null);
   if (beforeRequestCallback != null && modifications.contains(action)) {
     var value;
     if (action == 'add') value = data['data'];
     else if (action == 'change') value = data['change'];
     else if (action == 'remove') value = {};
     beforeRequest = beforeRequestCallback(value, data['args']);
   }

   DataProvider dp;

   return beforeRequest
     .then((_) => generator(data['args']))
     .then((DataProvider _dp) {
       dp = _dp;
       if (action == "get_data") {
         return dp.data().then((result) {
           stopWatch(watchID);
           return result;
         });
       }
       else if(action == "get_diff") {
         return dp.diffFromVersion(reqVersion)
           .then((result) {
               stopWatch(watchID);
               return result;
            });
       }
       else if (action == "add") {
         return dp.add(data['data'], data['author'])
         .then((result) {
           stopWatch(watchID);
           return result;
         });
       }
       else if (action == "change") {
         return dp.change(data['_id'], data['change'], data['author'])
             .then((result) {
               stopWatch(watchID);
               return result;
             });
       }
       else if (action == "remove") {
         return dp.remove(data['_id'], data['author'])
             .then((result) {
               stopWatch(watchID);
               return result;
             });
       }
     });

 }

 Resource(this.generator, this.beforeRequestCallback);
}