Implement Play Back about robobuggy HOT 5 CLOSED

This will be implemented as part of the pub/sub system. Similar to ROS, I think we should allow threads to subscribe callbacks to string paths.

For example, the serial event handler will publish to "/
An over-excited logger can subscribe to "/" and get every single message possible.
The GUI pane for IMU can subscribe to "/sensors/IMU", or whatever the IMU serial reader writes to. Alternatively, for playback, a sensor log reader can publish to "/sensor/IMU", and no other component in the system would be the wiser. This allows us have cleanly-implemented playback

(side note: There are global clock concerns during replay. We'll get to that.)

I am not positive this is the best strategy. There isn't compile-time type-safety with this approach, e.g., nothing stops an IMUMessage from being published to "/sensors/GPS", which will cause the GPSListeners to explode or become very confused.

Interface

abstract class IMessage {
// no data members required...not sure I like this. 
}

class ImuMessage extends IMessage {
   float X_acceleration;
   float Y_acceleration;
}

void publish(String path, IMessage msg);

public interface IListener {
   // should we know what the message was that called us?
   //   for example, the everything-logger would want to know what message it is logging  
   public void messageCallback(IMessage msg)
}


void subscribe(String path, IListener callback);

@TrevorDecker thoughts?

from robobuggy.

oh! java can parametrize types! i'll update that soon.

ros deets: http://pharos.ece.utexas.edu/wiki/index.php/How_to_Publish_and_Subscribe_to_a_Custom_Topic_and_Message_using_ROSJava

from robobuggy.

Java type parameters don't do much in our case. Our flexibility comes from being able to subscribe to arbitrary message paths, and we can't do that as easily if we have compile-time checking.

Other Design thoughts?
@ihartwig @bstrysko @Ginto8 @kbrennan234 @ayeohmy

from robobuggy.

I vote we get version 0.1 kind of working and worry about type safety latter. Run time should be fine we will just have to test our code for full coverage, which is a good thing anyway.

from robobuggy.

commit 272e491 prototypes the pubsub that's helping with cleanup. This will soon be part of the replay mechanism.

from robobuggy.