Implement event handler base class that broadcasts everything

lib/tfw/__init__.py

@@ -1,6 +1,6 @@
 # Copyright (C) 2018 Avatao.com Innovative Learning Kft.
 # All Rights Reserved. See LICENSE file for details.
 
-from .event_handler_base import EventHandlerBase, TriggeredEventHandler
+from .event_handler_base import EventHandlerBase, TriggeredEventHandler, BroadcastingEventHandler
 from .fsm_base import FSMBase
 from .linear_fsm import LinearFSM

lib/tfw/event_handler_base.py

@@ -2,8 +2,13 @@
 # All Rights Reserved. See LICENSE file for details.
 
 from abc import ABC, abstractmethod
+from json import dumps
+from hashlib import md5
 
 from tfw.networking.event_handlers import ServerConnector
+from tfw.config.logs import logging
+
+LOG = logging.getLogger(__name__)
 
 
 class EventHandlerBase(ABC):
@@ -28,12 +33,14 @@ class EventHandlerBase(ABC):
         """
         response = self.dispatch_handling(message)
         if response:
-            response['key'] = message['key']
             self.server_connector.send(response)
 
     def dispatch_handling(self, message):
         """
         Used to dispatch messages to their specific handlers.
+
+        :param message: the message received
+        :returns: the message to send back
         """
         if message['key'] != 'reset':
             return self.handle_event(message)
@@ -45,6 +52,7 @@ class EventHandlerBase(ABC):
         Abstract method that implements the handling of messages.
 
         :param message: the message received
+        :returns: the message to send back
         """
         raise NotImplementedError
 
@@ -54,6 +62,7 @@ class EventHandlerBase(ABC):
         Usually 'reset' events receive some sort of special treatment.
 
         :param message: the message received
+        :returns: the message to send back
         """
         return None
 
@@ -100,3 +109,38 @@ class TriggeredEventHandler(EventHandlerBase, ABC):
         if message.get('trigger') == self.trigger:
             return super().dispatch_handling(message)
         return None
+
+
+class BroadcastingEventHandler(EventHandlerBase, ABC):
+    # pylint: disable=abstract-method
+    """
+    Abstract base class for EventHandlers which broadcast responses
+    and intelligently ignore their own broadcasted messages they receive.
+    """
+    def __init__(self, key):
+        super().__init__(key)
+        self.own_message_hashes = []
+
+    def event_handler_callback(self, message):
+        message_hash = self.hash_message(message)
+
+        if message_hash in self.own_message_hashes:
+            self.own_message_hashes.remove(message_hash)
+            return
+
+        response = self.dispatch_handling(message)
+        if response:
+            self.own_message_hashes.append(self.hash_message(response))
+            self.server_connector.send(self.make_broadcast_message(response))
+
+    @staticmethod
+    def hash_message(message):
+        message_bytes = dumps(message, sort_keys=True).encode()
+        return md5(message_bytes).hexdigest()
+
+    @staticmethod
+    def make_broadcast_message(message):
+        return {
+            'key': 'broadcast',
+            'data': message
+        }