users: use dispatch_many_filter when sending USER_UPDATE events

Related to #19.

 - dispatcher: add EventDispatcher.dispatch_many_filter
 - pubsub.channel, guild: return session ids on dispatch() return
 - pubsub.friend, user: add dispatch_filter handler

litecord/blueprints/users.py

@@ -197,18 +197,33 @@ async def patch_me():
     user.pop('password_hash')
 
     public_user = await app.storage.get_user(user_id)
-    await app.dispatcher.dispatch_user(
-        user_id, 'USER_UPDATE', public_user)
+    session_ids = []
+
+    # by using dispatch_with_filter
+    # we're guaranteeing all shards will get
+    # a USER_UPDATE once and not any others.
+    session_ids.extend(
+        await app.dispatcher.dispatch_user(
+            user_id, 'USER_UPDATE', public_user)
+    )
 
     guild_ids = await app.user_storage.get_user_guilds(user_id)
     friend_ids = await app.user_storage.get_friend_ids(user_id)
 
-    await app.dispatcher.dispatch_many(
-        'guild', guild_ids, 'USER_UPDATE', public_user
+    session_ids.extend(
+        await app.dispatcher.dispatch_many_filter(
+            'guild', guild_ids,
+            lambda sess_id: sess_id not in session_ids,
+            'USER_UPDATE', public_user
+        )
     )
 
-    await app.dispatcher.dispatch_many(
-        'friend', friend_ids, 'USER_UPDATE', public_user
+    session_ids.extend(
+        await app.dispatcher.dispatch_many_filter(
+            'friend', friend_ids,
+            lambda sess_id: sess_id not in session_ids,
+            'USER_UPDATE', public_user
+        )
     )
 
     return jsonify(user)

litecord/dispatcher.py

@@ -114,6 +114,21 @@ class EventDispatcher:
         key = backend.KEY_TYPE(key)
         return await backend.dispatch_filter(key, func, *args)
 
+    async def dispatch_many_filter(self, backend_str, keys: List[Any],
+                                   func, *args) -> List[str]:
+        """Call the dispatch_filter method to many keys.
+
+        Not all backends will handle this function.
+        """
+        res = []
+
+        for key in keys:
+            res.extend(
+                await self.dispatch_filter(backend_str, key, func, *args)
+            )
+
+        return res
+
     async def reset(self, backend_str: str, key: Any):
         """Reset the bucket in the given backend."""
         backend = self.backends[backend_str]

litecord/pubsub/channel.py

@@ -19,6 +19,7 @@ class ChannelDispatcher(DispatcherWithState):
         # and store the number of states we dispatched the event to
         user_ids = self.state[channel_id]
         dispatched = 0
+        sessions = []
 
         # making a copy of user_ids since
         # we'll modify it later on.
@@ -42,7 +43,12 @@ class ChannelDispatcher(DispatcherWithState):
                 await self.unsub(channel_id, user_id)
                 continue
 
-            dispatched += await self._dispatch_states(states, event, data)
+            cur_sess = await self._dispatch_states(states, event, data)
+
+            sessions.extend(cur_sess)
+            dispatched += len(cur_sess)
 
         log.info('Dispatched chan={} {!r} to {} states',
                  channel_id, event, dispatched)
+
+        return sessions

litecord/pubsub/dispatcher.py

@@ -65,16 +65,16 @@ class Dispatcher:
 
     async def _dispatch_states(self, states: list, event: str, data) -> int:
         """Dispatch an event to a list of states."""
-        dispatched = 0
+        res = []
 
         for state in states:
             try:
                 await state.ws.dispatch(event, data)
-                dispatched += 1
+                res.append(state.session_id)
             except:
                 log.exception('error while dispatching')
 
-        return dispatched
+        return res
 
 
 class DispatcherWithState(Dispatcher):

litecord/pubsub/friend.py

@@ -15,18 +15,27 @@ class FriendDispatcher(DispatcherWithState):
     KEY_TYPE = int
     VAL_TYPE = int
 
-    async def dispatch(self, user_id: int, event, data):
+    async def dispatch_filter(self, user_id: int, func, event, data):
         """Dispatch an event to all of a users' friends."""
-        # all friends that are connected and subscribed
-        # to the one we're dispatching from
         peer_ids = self.state[user_id]
-        dispatched = 0
+        sessions = []
 
         for peer_id in peer_ids:
             # dispatch to the user instead of the "shards tied to a guild"
             # since relationships broadcast to all shards.
-            dispatched += await self.main_dispatcher.dispatch(
-                'user', peer_id, event, data)
+            sessions.extend(
+                await self.main_dispatcher.dispatch_filter(
+                    'user', peer_id, func, event, data)
+            )
 
         log.info('dispatched uid={} {!r} to {} states',
-                 user_id, event, dispatched)
+                 user_id, event, len(sessions))
+
+        return sessions
+
+    async def dispatch(self, user_id, event, data):
+        return await self.dispatch_filter(
+            user_id,
+            lambda sess_id: True,
+            event, data,
+        )

litecord/pubsub/guild.py

@@ -63,6 +63,7 @@ class GuildDispatcher(DispatcherWithState):
         func(session_id) true."""
         user_ids = self.state[guild_id]
         dispatched = 0
+        sessions = []
 
         # acquire a copy since we may be modifying
         # the original user_ids
@@ -82,16 +83,20 @@ class GuildDispatcher(DispatcherWithState):
                 lambda state: func(state.session_id), states
             ))
 
-            dispatched += await self._dispatch_states(
+            cur_sess = await self._dispatch_states(
                 states, event, data)
+            sessions.extend(cur_sess)
+            dispatched += len(cur_sess)
 
         log.info('Dispatched {} {!r} to {} states',
                  guild_id, event, dispatched)
 
+        return sessions
+
     async def dispatch(self, guild_id: int,
                        event: str, data: Any):
         """Dispatch an event to all subscribers of the guild."""
-        await self.dispatch_filter(
+        return await self.dispatch_filter(
             guild_id,
             lambda sess_id: True,
             event, data,

litecord/pubsub/user.py

@@ -5,7 +5,20 @@ class UserDispatcher(Dispatcher):
     """User backend for Pub/Sub."""
     KEY_TYPE = int
 
-    async def dispatch(self, user_id: int, event, data):
+    async def dispatch_filter(self, user_id: int, func, event, data):
         """Dispatch an event to all shards of a user."""
-        states = self.sm.user_states(user_id)
+
+        # filter only states where func() gives true
+        states = list(filter(
+            lambda state: func(state.session_id),
+            self.sm.user_states(user_id)
+        ))
+
         return await self._dispatch_states(states, event, data)
+
+    async def dispatch(self, user_id: int, event, data):
+        return await self.dispatch_filter(
+            user_id,
+            lambda sess_id: True,
+            event, data,
+        )