Ensure each in-use channel has a cached claimant on init

This avoids issues when a user tries to close a channel, but the cache is empty, so the author check fails.

2 files changed, 35 insertions, 0 deletions

diff --git a/bot/exts/help_channels/_channel.py b/bot/exts/help_channels/_channel.py
index e43c1e789..ff9e6a347 100644
--- a/bot/exts/help_channels/_channel.py
+++ b/bot/exts/help_channels/_channel.py
@@ -1,3 +1,4 @@
+import re
 import typing as t
 from datetime import timedelta
 from enum import Enum
@@ -16,6 +17,7 @@ log = get_logger(__name__)
 
 MAX_CHANNELS_PER_CATEGORY = 50
 EXCLUDED_CHANNELS = (constants.Channels.cooldown,)
+CLAIMED_BY_RE = re.compile(r"Channel claimed by <@!?(?P<user_id>\d{17,20})>\.$")
 
 
 class ClosingReason(Enum):
@@ -157,3 +159,35 @@ async def move_to_bottom(channel: discord.TextChannel, category_id: int, **optio
     # Now that the channel is moved, we can edit the other attributes
     if options:
         await channel.edit(**options)
+
+
+async def ensure_cached_claimant(channel: discord.TextChannel) -> None:
+    """
+    Ensure there is a claimant cached for each help channel.
+
+    Check the redis cache first, return early if there is already a claimant cached.
+    If there isn't an entry in redis, search for the "Claimed by X." embed in channel history.
+        Stopping early if we discover a dormant message first.
+
+    If a claimant could not be found, send a warning to #helpers and set the claimant to the bot.
+    """
+    if await _caches.claimants.get(channel.id):
+        return
+
+    async for message in channel.history(limit=1000):
+        if message.author.id != bot.instance.user.id:
+            # We only care about bot messages
+            continue
+        if message.embeds:
+            if _message._match_bot_embed(message, _message.DORMANT_MSG):
+                log.info("Hit the dormant message embed before finding a claimant in %s (%d).", channel, channel.id)
+                break
+            user_id = CLAIMED_BY_RE.match(message.embeds[0].description).group("user_id")
+            await _caches.claimants.set(channel.id, int(user_id))
+            return
+
+    await bot.instance.get_channel(constants.Channels.helpers).send(
+        f"I couldn't find a claimant for {channel.mention} in that last 1000 messages. "
+        "Please use your helper powers to close the channel if/when appropriate."
+    )
+    await _caches.claimants.set(channel.id, bot.instance.user.id)
diff --git a/bot/exts/help_channels/_cog.py b/bot/exts/help_channels/_cog.py
index 6d061c8ca..b0f1a1dce 100644
--- a/bot/exts/help_channels/_cog.py
+++ b/bot/exts/help_channels/_cog.py
@@ -326,6 +326,7 @@ class HelpChannels(commands.Cog):
 
         log.trace("Moving or rescheduling in-use channels.")
         for channel in _channel.get_category_channels(self.in_use_category):
+            await _channel.ensure_cached_claimant(channel)
             await self.move_idle_channel(channel, has_task=False)
 
         # Prevent the command from being used until ready.