There needs to be a deterministic way to determine when a metaSignal command has completed

[chefsteph9]

Currently, there is just a timer after the dataHub.megaSignalCommand is issued to make sure that it has been executed. This is non-deterministic and is not guaranteed to work. There needs to be a way for the DataHub to let the web page know when the MetaSignalCommand has executed.

An example of code that uses a timer when a better solution is needed is the addNewSignals function in
io-mapping-scripts.js:

    $scope.addNewSignals = function () {
        var promises = [];
        $.each($scope.mapping.Type.Fields, function (i, f) {
            var ms = {
                'AnalyticProjectName': $('#proj' + f.Identifier).val(),
                'AnalyticInstanceName': $('#inst' + f.Identifier).val(),
                'DeviceID': '00000000-0000-0000-0000-000000000000',
                'RuntimeID': 0,
                'SignalID': $('#signalID' + f.Identifier).val(),
                'PointTag': $('#point' + f.Identifier).val(),
                'SignalType': $('#type' + f.Identifier).val(),
                'Description': $('#desc' + f.Identifier).val()
            }
            $scope.mapping.FieldMappings[i].Expression = $('#point' + f.Identifier).val();
            promises.push(dataHub.metaSignalCommand(ms));
        });

        $(promises).whenAll().done(function () {
            // TODO: The setTimout is a temporary solution. A more permanent solution would involve maintaining a count of the number of metasignals sent and received
            // and refreshing the metadata when we know that all metasignal commands have been executed sucessfully.
            setTimeout(function () {  
                $(window).one('metaDataReceived', function () {  
                    dataHub.getMeasurementDetails().done(function (md) {
                        $.each($scope.mapping.Type.Fields, function (i, f) {
                            var signals = $.grep(md, function (d) { return d.PointTag == $('#point' + f.Identifier).val() });
                            if (signals.length > 0) {
                                $('#signalID' + f.Identifier).val(signals[0].SignalID);
                            }
                        });
                    });
                });
                dataHub.refreshMetaData();
            }, 1100); // If it's not working, make this number bigger. See: TODO above.
        });
        $scope.signalsAdded = true;
        $('#signalDialog').modal('hide');
    }