vertx event bus addition

caller_example.js

eventBus.replaceData("address", "read-action", "replace-action", {
  "id" : 15
},
// action on replace computation
function (readData) {
  var replacedData = readData;
  replacedData.nickname = replacedData.nickname.toLowerCase();
  return replacedData;
},
// action on success
function () {
  console.log('success!');
},
// action on error (data not foundm, module doesn't support these actions, ...)
function (error) {
  console.log('fail: ' + error);
})

eventBusAddition.js

eventBus = {
  // new eventbus function 'replace'
  replaceData : function replaceData(address, readAction, replaceAction, toRead, replaceComputation, success, failure) {
    function callbackForData(data) {
      eventBus.send(address, { action: readAction, data: readData }, function(readReply) {
        if (readReply.status === 'ok') {
          var replacedData = replaceComputation(readReply.data);
          eventBus.replace(address, { action: replaceAction, oldData: data, newData: replacedData }, function(replaceReply) {
            if (replaceReply.status === 'ok') {
              // successfully replaced!
              onSuccess();
            } else if (replaceReply.status === 'replace-error') {
              // try again, some concurrent action changed it
              callbackForData(data);
            } else {
              // some other error occurred, tell error callback
              onFailure(replaceReply.error);
            }
          });
        } else {
          // some other error occurred, tell error callback
          onFailure(readReply.error);
        }
      });
    }

    callbackForData(toRead);
  }
}