Refactor EventHandlerBase to be more general

lib/tfw/event_handler_base.py

@@ -17,12 +17,15 @@ class EventHandlerBase(ABC):
     def __init__(self, key):
         self.server_connector = ServerConnector()
         self.key = key
-        self.subscriptions = set()
-        self.subscribe(self.key)
-        self.subscribe('reset')
+        self.subscribe(self.key, 'reset')
         self.server_connector.register_callback(self.event_handler_callback)
 
     def event_handler_callback(self, msg_parts):
+        """
+        Callback that is invoked when receiving a message.
+        This is subscribed in __init__().
+        """
+        # TODO: fix faulty logic below
         message = deserialize_tfw_msg(*msg_parts)
         response = self.dispatch_handling(message)
         response['key'] = message['key']
@@ -37,31 +40,49 @@ class EventHandlerBase(ABC):
 
     @abstractmethod
     def handle_event(self, message):
+        """
+        Abstract method that implements the handling of messages.
+
+        :param message: the message received
+        """
         raise NotImplementedError
 
     def handle_reset(self, message):
         # pylint: disable=unused-argument,no-self-use
+        """
+        'reset' events usually receive some sort of special treatment.
+
+        :param message: the message received
+        """
         return None
 
-    def cleanup(self):
-        pass
-
-    def subscribe(self, key):
-        if key not in self.subscriptions:
-            self.subscriptions.add(key)
+    def subscribe(self, *keys):
+        """
+        Subscribe this EventHandler to receive events for given keys.
+        Note that you can subscribe to the same key several times in which
+        case you will need to unsubscribe multiple times in order to stop
+        receiving events.
+        
+        :param keys: list of keys to subscribe to
+        """
+        for key in keys:
             self.server_connector.subscribe(key)
 
-    def unsubscribe(self, key):
-        try:
-            self.subscriptions.remove(key)
-            self.server_connector.unsubscribe(key)
-        except KeyError:
-            pass
+    def unsubscribe(self, *keys):
+        """
+        Unsubscribe this eventhandler from the given keys.
 
-    def unsubscribe_all(self):
-        for sub in self.subscriptions:
-            self.server_connector.unsubscribe(key=sub)
-        self.subscriptions.clear()
+        :param keys: list of keys to unsubscribe from
+        """
+        for key in keys:
+            self.server_connector.unsubscribe(key)
+
+    def cleanup(self):
+        """
+        Perform cleanup actions such as releasing database
+        connections and stuff like that.
+        """
+        pass
 
 
 class TriggeredEventHandler(EventHandlerBase, ABC):