Incidents: implement & schedule `crawl_incidents` task

See docstring for further information. This will run on start-up
to retroactively add missing emoji.

Ratelimit-wise this should be fine, as there should never be too
many missing emoji.

1 files changed, 32 insertions, 0 deletions

diff --git a/bot/cogs/moderation/incidents.py b/bot/cogs/moderation/incidents.py
index 91b949173..e773636e7 100644
--- a/bot/cogs/moderation/incidents.py
+++ b/bot/cogs/moderation/incidents.py
@@ -1,3 +1,4 @@
+import asyncio
 import logging
 import typing as t
 from enum import Enum
@@ -27,7 +28,38 @@ class Incidents(Cog):
     """Automation for the #incidents channel."""
 
     def __init__(self, bot: Bot) -> None:
+        """Schedule `crawl_task` on start-up."""
         self.bot = bot
+        self.crawl_task = self.bot.loop.create_task(self.crawl_incidents())
+
+    async def crawl_incidents(self) -> None:
+        """
+        Crawl #incidents and add missing emoji where necessary.
+
+        This is to catch-up should an incident be reported while the bot wasn't listening.
+        Internally, we simply walk the channel history and pass each message to `on_message`.
+
+        In order to avoid drowning in ratelimits, we take breaks after each message.
+
+        Once this task is scheduled, listeners should await it. The crawl assumes that
+        the channel history doesn't change as we go over it.
+        """
+        await self.bot.wait_until_guild_available()
+        incidents: discord.TextChannel = self.bot.get_channel(Channels.incidents)
+
+        # Limit the query at 50 as in practice, there should never be this many messages,
+        # and if there are, something has likely gone very wrong
+        limit = 50
+
+        # Seconds to sleep after each message
+        sleep = 2
+
+        log.debug(f"Crawling messages in #incidents: {limit=}, {sleep=}")
+        async for message in incidents.history(limit=limit):
+            await self.on_message(message)
+            await asyncio.sleep(sleep)
+
+        log.debug("Crawl task finished!")
 
     @staticmethod
     async def add_signals(incident: discord.Message) -> None: