[V3 RPC] Add basic RPC functionality (#1017)

* Add basic RPC functionality

* Add load/unload/reload rpc commands

* Reorganize without rpc_ready event

* Remove rpc ready event

* Removed bot reference from rpc module

* Close RPC server cleanly

* refactor bot

* Refactor a bit and make RPC server initialization based on a cli flag

* Fix version resolver

* standardize version getters

* Pick a new port number

redbot/core/bot.py

@@ -10,10 +10,29 @@ from discord.ext.commands.bot import BotBase
 from discord.ext.commands import GroupMixin
 
 from .cog_manager import CogManager
-from . import Config, i18n, RedContext
+from . import (
+    Config,
+    i18n,
+    RedContext,
+    rpc
+)
+
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from aiohttp_json_rpc import JsonRpc
 
 
-class RedBase(BotBase):
+# noinspection PyUnresolvedReferences
+class RpcMethodMixin:
+    async def rpc__cogs(self, request):
+        return list(self.cogs.keys())
+
+    async def rpc__extensions(self, request):
+        return list(self.extensions.keys())
+
+
+class RedBase(BotBase, RpcMethodMixin):
     """Mixin for the main bot class.
 
     This exists because `Red` inherits from `discord.AutoShardedClient`, which
@@ -26,6 +45,7 @@ class RedBase(BotBase):
         self._shutdown_mode = ExitCodes.CRITICAL
         self.db = Config.get_core_conf(force_registration=True)
         self._co_owners = cli_flags.co_owner
+        self.rpc_enabled = cli_flags.rpc
 
         self.db.register_global(
             token=None,
@@ -73,6 +93,8 @@ class RedBase(BotBase):
 
         self.cog_mgr = CogManager(paths=(str(self.main_dir / 'cogs'),))
 
+        self.register_rpc_methods()
+
         super().__init__(**kwargs)
 
     async def _dict_abuse(self, indict):
@@ -194,6 +216,10 @@ class RedBase(BotBase):
             del self.extensions[name]
             # del sys.modules[name]
 
+    def register_rpc_methods(self):
+        rpc.add_method('bot', self.rpc__cogs)
+        rpc.add_method('bot', self.rpc__extensions)
+
 
 class Red(RedBase, discord.AutoShardedClient):
     """