Support to register/unregister custom handlers on the bus.

platypush/bus/__init__.py

@@ -1,15 +1,34 @@
+from collections import defaultdict
+from dataclasses import dataclass, field
 import logging
 import threading
 import time
 
 from queue import Queue, Empty
-from typing import Callable, Type
+from typing import Callable, Dict, Iterable, Type
 
+from platypush.message import Message
 from platypush.message.event import Event
 
 logger = logging.getLogger('platypush:bus')
 
 
+@dataclass
+class MessageHandler:
+    """
+    Wrapper for a message callback handler.
+    """
+
+    msg_type: Type[Message]
+    callback: Callable[[Message], None]
+    kwargs: dict = field(default_factory=dict)
+
+    def match(self, msg: Message) -> bool:
+        return isinstance(msg, self.msg_type) and all(
+            getattr(msg, k, None) == v for k, v in self.kwargs.items()
+        )
+
+
 class Bus:
     """
     Main local bus where the daemon will listen for new messages.
@@ -21,7 +40,10 @@ class Bus:
         self.bus = Queue()
         self.on_message = on_message
         self.thread_id = threading.get_ident()
-        self.event_handlers = {}
+        self.handlers: Dict[
+            Type[Message], Dict[Callable[[Message], None], MessageHandler]
+        ] = defaultdict(dict)
+
         self._should_stop = threading.Event()
 
     def post(self, msg):
@@ -38,26 +60,24 @@ class Bus:
     def stop(self):
         self._should_stop.set()
 
+    def _get_matching_handlers(
+        self, msg: Message
+    ) -> Iterable[Callable[[Message], None]]:
+        return [
+            hndl.callback
+            for cls in type(msg).__mro__
+            for hndl in self.handlers.get(cls, [])
+            if hndl.match(msg)
+        ]
+
     def _msg_executor(self, msg):
         def event_handler(event: Event, handler: Callable[[Event], None]):
             logger.info('Triggering event handler %s', handler.__name__)
             handler(event)
 
         def executor():
-            if isinstance(msg, Event):
-                handlers = self.event_handlers.get(
-                    type(msg),
-                    {
-                        *[
-                            hndl
-                            for event_type, hndl in self.event_handlers.items()
-                            if isinstance(msg, event_type)
-                        ]
-                    },
-                )
-
-                for hndl in handlers:
-                    threading.Thread(target=event_handler, args=(msg, hndl))
+            for hndl in self._get_matching_handlers(msg):
+                threading.Thread(target=event_handler, args=(msg, hndl)).start()
 
             try:
                 if self.on_message:
@@ -100,27 +120,25 @@ class Bus:
         logger.info('Bus service stopped')
 
     def register_handler(
-        self, event_type: Type[Event], handler: Callable[[Event], None]
+        self, type: Type[Message], handler: Callable[[Message], None], **kwargs
     ) -> Callable[[], None]:
         """
-        Register an event handler to the bus.
+        Register a generic handler to the bus.
 
-        :param event_type: Event type to subscribe (event inheritance also works).
-        :param handler: Event handler - a function that takes an Event object as parameter.
+        :param type: Type of the message to subscribe to (event inheritance also works).
+        :param handler: Event handler - a function that takes a Message object as parameter.
+        :param kwargs: Extra filter on the message values.
         :return: A function that can be called to remove the handler (no parameters required).
         """
-        if event_type not in self.event_handlers:
-            self.event_handlers[event_type] = set()
-
-        self.event_handlers[event_type].add(handler)
+        self.handlers[type][handler] = MessageHandler(type, handler, kwargs)
 
         def unregister():
-            self.unregister_handler(event_type, handler)
+            self.unregister_handler(type, handler)
 
         return unregister
 
     def unregister_handler(
-        self, event_type: Type[Event], handler: Callable[[Event], None]
+        self, type: Type[Message], handler: Callable[[Message], None]
     ) -> None:
         """
         Remove an event handler.
@@ -128,14 +146,12 @@ class Bus:
         :param event_type: Event type.
         :param handler: Existing event handler.
         """
-        if event_type not in self.event_handlers:
+        if type not in self.handlers:
             return
 
-        if handler in self.event_handlers[event_type]:
-            self.event_handlers[event_type].remove(handler)
-
-        if len(self.event_handlers[event_type]) == 0:
-            del self.event_handlers[event_type]
+        self.handlers[type].pop(handler, None)
+        if len(self.handlers[type]) == 0:
+            del self.handlers[type]
 
 
 # vim:sw=4:ts=4:et: