feat(core): Channel hook manager.

src/core/cog.py

@@ -1,5 +1,6 @@
 from typing import Optional
 from collections import defaultdict
+from weakref import WeakValueDictionary
 
 import discord
 import discord.app_commands as appcmd
@@ -16,6 +17,7 @@ from .lion import Lions
 from .lion_guild import GuildConfig
 from .lion_member import MemberConfig
 from .lion_user import UserConfig
+from .hooks import HookedChannel
 
 
 class keydefaultdict(defaultdict):
@@ -54,6 +56,7 @@ class CoreCog(LionCog):
         self.app_cmd_cache: list[discord.app_commands.AppCommand] = []
         self.cmd_name_cache: dict[str, discord.app_commands.AppCommand] = {}
         self.mention_cache: dict[str, str] = keydefaultdict(self.mention_cmd)
+        self.hook_cache: WeakValueDictionary[int, HookedChannel] = WeakValueDictionary()
 
     async def cog_load(self):
         # Fetch (and possibly create) core data rows.
@@ -91,7 +94,7 @@ class CoreCog(LionCog):
                 cache |= subcache
         return cache
 
-    def mention_cmd(self, name):
+    def mention_cmd(self, name: str):
         """
         Create an application command mention for the given names.
 
@@ -103,6 +106,12 @@ class CoreCog(LionCog):
             mention = f"</{name}:1110834049204891730>"
         return mention
 
+    def hooked_channel(self, channelid: int):
+        if (hooked := self.hook_cache.get(channelid, None)) is None:
+            hooked = HookedChannel(self.bot, channelid)
+            self.hook_cache[channelid] = hooked
+        return hooked
+
     async def cog_unload(self):
         await self.bot.remove_cog(self.lions.qualified_name)
         self.bot.remove_listener(self.shard_update_guilds, name='on_guild_join')

src/core/hooks.py

@@ -0,0 +1,106 @@
+from typing import Optional
+import logging
+import asyncio
+
+import discord
+
+from meta import LionBot
+
+from .data import CoreData
+
+logger = logging.getLogger(__name__)
+
+
+MISSING = discord.utils.MISSING
+
+
+class HookedChannel:
+    def __init__(self, bot: LionBot, channelid: int):
+        self.bot = bot
+        self.channelid = channelid
+
+        self.webhook: Optional[discord.Webhook] | MISSING = None
+        self.data: Optional[CoreData.LionHook] = None
+
+        self.lock = asyncio.Lock()
+
+    @property
+    def channel(self) -> Optional[discord.TextChannel | discord.VoiceChannel | discord.StageChannel]:
+        if not self.bot.is_ready():
+            raise ValueError("Cannot get hooked channel before ready.")
+        channel = self.bot.get_channel(self.channelid)
+        if channel and not isinstance(channel, (discord.TextChannel, discord.VoiceChannel, discord.StageChannel)):
+            raise ValueError(f"Hooked channel expects GuildChannel not '{channel.__class__.__name__}'")
+        return channel
+
+    async def get_webhook(self) -> Optional[discord.Webhook]:
+        """
+        Fetch the saved discord.Webhook for this channel.
+
+        Uses cached webhook if possible, but instantiates if required.
+        Does not create a new webhook, use `create_webhook` for that.
+        """
+        async with self.lock:
+            if self.webhook is MISSING:
+                hook = None
+            elif self.webhook is None:
+                # Fetch webhook data
+                data = await CoreData.LionHook.fetch(self.channelid)
+                if data is not None:
+                    # Instantiate Webhook
+                    hook = self.webhook = data.as_webhook(client=self.bot)
+                else:
+                    self.webhook = MISSING
+                    hook = None
+            else:
+                hook = self.webhook
+
+            return hook
+
+    async def create_webhook(self, **creation_kwargs) -> Optional[discord.Webhook]:
+        """
+        Create and save a new webhook in this channel.
+
+        Returns None if we could not create a new webhook.
+        """
+        async with self.lock:
+            if self.webhook is not MISSING:
+                # Delete any existing webhook
+                if self.webhook is not None:
+                    try:
+                        await self.webhook.delete()
+                    except discord.HTTPException as e:
+                        logger.info(
+                            f"Ignoring exception while refreshing webhook for {self.channelid}: {repr(e)}"
+                        )
+                await self.bot.core.data.LionHook.table.delete_where(channelid=self.channelid)
+                self.webhook = MISSING
+                self.data = None
+
+            channel = self.channel
+            if channel is not None and channel.permissions_for(channel.guild.me).manage_webhooks:
+                if 'avatar' not in creation_kwargs:
+                    avatar = self.bot.user.avatar if self.bot.user else None
+                    creation_kwargs['avatar'] = (await avatar.to_file()).fp.read() if avatar else None
+                webhook = await channel.create_webhook(**creation_kwargs)
+                self.data = await self.bot.core.data.LionHook.create(
+                    channelid=self.channelid,
+                    token=webhook.token,
+                    webhookid=webhook.id,
+                )
+                self.webhook = webhook
+                return webhook
+
+    async def invalidate(self, webhook: discord.Webhook):
+        """
+        Invalidate the given webhook.
+
+        To be used when the webhook has been deleted on the Discord side.
+        """
+        async with self.lock:
+            if self.webhook is not None and self.webhook is not MISSING and self.webhook.id == webhook.id:
+                # Webhook provided matches current webhook
+                # Delete current webhook
+                self.webhook = MISSING
+                self.data = None
+            await self.bot.core.data.LionHook.table.delete_where(webhookid=webhook.id)