Using TCU Activity Manager APIs to get TCU activity state updates

The below steps need to be followed by applications to listen to TCU-activity state notifications, for performing any tasks before the state transition.

### 1. Implement ITcuActivityListener and IServiceStatusListener interface ###

class MyTcuActivityStateListener : public ITcuActivityListener,
                                   public IServiceStatusListener {
public:
    void onTcuActivityStateUpdate(TcuActivityState state) override;
    void onServiceStatusChange(ServiceStatus status) override;
};

### 2. Get the Power-Factory instance ###

auto &powerFactory = PowerFactory::getInstance();

### 3. Get TCU-activity manager instance ###

auto tcuActivityManager = powerFactory.getTcuActivityManager();

### 4. Wait for the TCU-activity management services to be initialized and ready ###

bool isReady = tcuActivityManager->isReady();
if(!isReady) {
    std::cout << "TCU-activity management service is not ready" << std::endl;
    std::cout << "Waiting uncondotionally for it to be ready " << std::endl;
    std::future<bool> f = tcuActivityManager->onReady();
    isReady = f.get();
}

### 5. Exit the application, if SDK is unable to initialize TCU-activity management service ###

if(isReady) {
    std::cout << " *** TCU-activity management service is Ready *** " << std::endl;
} else {
    std::cout << " *** ERROR - Unable to initialize TCU-activity management service" << std::endl;
    return 1;
}

### 6. Instantiate MyTcuActivityStateListener ###

auto myTcuStateListener = std::make_shared<MyTcuActivityStateListener>();

### 7. Register for updates on TCU-activity state and its management service status ###

tcuActivityManager->registerListener(myTcuStateListener);
tcuActivityManager->registerServiceStateListener(myTcuStateListener);

### 8. Wait for the TCU-activity state updates ###

void MyTcuActivityStateListener::onTcuActivityStateUpdate(TcuActivityState state) {
    std::cout << std::endl << "********* TCU-activity state update *********" << std::endl;
    // Avoid long blocking calls when handling notifications
}

### 9. On SUSPEND/SHUTDOWN notification, save any required information and send one(despite multiple listeners) acknowledgement ###

tcuActivityManager->sendActivityStateAck(TcuActivityStateAck);

10. When the TCU-activity management service goes down, this API is invoked with status UNAVAILABLE. All TCU-activity state notifications will be stopped until the status becomes AVAILABLE again

void MyTcuActivityStateListener::onServiceStatusChange(ServiceStatus status) {
    std::cout << std::endl << "****** TCU-activity management service status update ******" << std::endl;
    // Avoid long blocking calls when handling notifications
}