gateway.websocket: account for sharding in _guild_ids

Closes #1

litecord/gateway/websocket.py

@@ -196,10 +196,9 @@ class GatewayWebsocket:
         await self.send(payload)
 
     async def _make_guild_list(self) -> List[int]:
-        # TODO: This function does not account for sharding.
         user_id = self.state.user_id
 
-        guild_ids = await self.storage.get_user_guilds(user_id)
+        guild_ids = await self._guild_ids()
 
         if self.state.bot:
             return [{
@@ -315,11 +314,23 @@ class GatewayWebsocket:
             raise InvalidShard('Shard count > Total shards')
 
     async def _guild_ids(self):
-        # TODO: account for sharding
-        return await self.storage.get_user_guilds(
+        guild_ids = await self.storage.get_user_guilds(
             self.state.user_id
         )
 
+        shard_id = self.state.current_shard
+        shard_count = self.state.shard_count
+
+        def _get_shard(guild_id):
+            return (guild_id >> 22) % shard_count
+
+        filtered = filter(
+            lambda guild_id: _get_shard(guild_id) == shard_id,
+            guild_ids
+        )
+
+        return list(filtered)
+
     async def subscribe_all(self):
         """Subscribe to all guilds, DM channels, and friends.