Implement a LRU cache for private channels.

Another fix related to the discord issue[1].

[1]: https://github.com/hammerandchisel/discord-api-docs/issues/184

discord/client.py

@@ -179,7 +179,13 @@ class Client:
 
     @property
     def private_channels(self):
-        """List[:class:`abc.PrivateChannel`]: The private channels that the connected client is participating on."""
+        """List[:class:`abc.PrivateChannel`]: The private channels that the connected client is participating on.
+
+        .. note::
+
+            This returns only up to 128 most recent private channels due to an internal working
+            on how Discord deals with private channels.
+        """
         return self._connection.private_channels
 
     @property

discord/state.py

@@ -37,7 +37,7 @@ from .calls import GroupCall
 from . import utils, compat
 from .embeds import Embed
 
-from collections import deque, namedtuple
+from collections import deque, namedtuple, OrderedDict
 import copy, enum, math
 import datetime
 import asyncio
@@ -89,7 +89,9 @@ class ConnectionState:
         self._calls = {}
         self._guilds = {}
         self._voice_clients = {}
-        self._private_channels = {}
+
+        # LRU of max size 128
+        self._private_channels = OrderedDict()
         # extra dict to look up private channels by user id
         self._private_channels_by_user = {}
         self._messages = deque(maxlen=self.max_messages)
@@ -189,13 +191,27 @@ class ConnectionState:
         return list(self._private_channels.values())
 
     def _get_private_channel(self, channel_id):
-        return self._private_channels.get(channel_id)
+        try:
+            value = self._private_channels[channel_id]
+        except KeyError:
+            return None
+        else:
+            self._private_channels.move_to_end(channel_id)
+            return value
 
     def _get_private_channel_by_user(self, user_id):
         return self._private_channels_by_user.get(user_id)
 
     def _add_private_channel(self, channel):
-        self._private_channels[channel.id] = channel
+        channel_id = channel.id
+        self._private_channels[channel_id] = channel
+
+        if len(self._private_channels) > 128:
+            _, to_remove = self._private_channels.popitem(last=False)
+            print(to_remove)
+            if isinstance(to_remove, DMChannel):
+                self._private_channels_by_user.pop(to_remove.recipient.id, None)
+
         if isinstance(channel, DMChannel):
             self._private_channels_by_user[channel.recipient.id] = channel