[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/core_commands.py

@@ -13,6 +13,12 @@ from discord.ext import commands
 
 from redbot.core import checks
 from redbot.core import i18n
+from redbot.core import rpc
+
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from redbot.core.bot import Red
 
 __all__ = ["Core"]
 
@@ -29,6 +35,12 @@ _ = i18n.CogI18n("Core", __file__)
 
 class Core:
     """Commands related to core functions"""
+    def __init__(self, bot):
+        self.bot = bot  # type: Red
+
+        rpc.add_method('core', self.rpc_load)
+        rpc.add_method('core', self.rpc_unload)
+        rpc.add_method('core', self.rpc_reload)
 
     @commands.command()
     @checks.is_owner()
@@ -410,3 +422,25 @@ class Core:
                              "to %s") % destination)
         else:
             await ctx.send(_("Message delivered to %s") % destination)
+
+    # RPC handlers
+    async def rpc_load(self, request):
+        cog_name = request.params[0]
+
+        spec = await self.bot.cog_mgr.find_cog(cog_name)
+        if spec is None:
+            raise LookupError("No such cog found.")
+
+        self.cleanup_and_refresh_modules(spec.name)
+
+        self.bot.load_extension(spec)
+
+    async def rpc_unload(self, request):
+        cog_name = request.params[0]
+
+        self.bot.unload_extension(cog_name)
+
+    async def rpc_reload(self, request):
+        await self.rpc_unload(request)
+        await self.rpc_load(request)
+