Silence: reschedule silences on startup

Remove the moderator notification when unloading the cog because. Its
purpose was to remind to manually unsilence channels. However, this
purpose is now obsolete due to automatic rescheduling.

The notification was buggy anyway due to a race condition with the bot
shutting down, and that'd be further complicated by having to
asynchronously retrieve channels from the redis cache too.

Fixes #1053

1 files changed, 32 insertions, 10 deletions

diff --git a/bot/cogs/moderation/silence.py b/bot/cogs/moderation/silence.py
index c43194511..02d8de29e 100644
--- a/bot/cogs/moderation/silence.py
+++ b/bot/cogs/moderation/silence.py
@@ -78,11 +78,14 @@ class Silence(commands.Cog):
     async def _get_instance_vars(self) -> None:
         """Get instance variables after they're available to get from the guild."""
         await self.bot.wait_until_guild_available()
+
         guild = self.bot.get_guild(Guild.id)
         self._verified_role = guild.get_role(Roles.verified)
         self._mod_alerts_channel = self.bot.get_channel(Channels.mod_alerts)
         self._mod_log_channel = self.bot.get_channel(Channels.mod_log)
         self.notifier = SilenceNotifier(self._mod_log_channel)
+        await self._reschedule()
+
         self._get_instance_vars_event.set()
 
     @commands.command(aliases=("hush",))
@@ -120,18 +123,21 @@ class Silence(commands.Cog):
         """
         await self._get_instance_vars_event.wait()
         log.debug(f"Unsilencing channel #{ctx.channel} from {ctx.author}'s command.")
+        await self._unsilence_wrapper(ctx.channel)
 
-        if not await self._unsilence(ctx.channel):
-            overwrite = ctx.channel.overwrites_for(self._verified_role)
+    async def _unsilence_wrapper(self, channel: TextChannel) -> None:
+        """Unsilence `channel` and send a success/failure message."""
+        if not await self._unsilence(channel):
+            overwrite = channel.overwrites_for(self._verified_role)
             if overwrite.send_messages is False and overwrite.add_reactions is False:
-                await ctx.send(
+                await channel.send(
                     f"{Emojis.cross_mark} current channel was not unsilenced because the current "
                     f"overwrites were set manually. Please edit them manually to unsilence."
                 )
             else:
-                await ctx.send(f"{Emojis.cross_mark} current channel was not silenced.")
+                await channel.send(f"{Emojis.cross_mark} current channel was not silenced.")
         else:
-            await ctx.send(f"{Emojis.check_mark} unsilenced current channel.")
+            await channel.send(f"{Emojis.check_mark} unsilenced current channel.")
 
     async def _silence(self, channel: TextChannel, persistent: bool, duration: Optional[int]) -> bool:
         """
@@ -199,13 +205,29 @@ class Silence(commands.Cog):
 
         return True
 
+    async def _reschedule(self) -> None:
+        """Reschedule unsilencing of active silences and add permanent ones to the notifier."""
+        for channel_id, timestamp in await self.muted_channel_times.items():
+            channel = self.bot.get_channel(channel_id)
+            if channel is None:
+                log.info(f"Can't reschedule silence for {channel_id}: channel not found.")
+                continue
+
+            if timestamp == -1:
+                log.info(f"Adding permanent silence for #{channel} ({channel.id}) to the notifier.")
+                self.notifier.add_channel(channel)
+                continue
+
+            dt = datetime.utcfromtimestamp(timestamp)
+            if dt <= datetime.utcnow():
+                await self._unsilence_wrapper(channel)
+            else:
+                log.info(f"Rescheduling silence for #{channel} ({channel.id}).")
+                self.scheduler.schedule_at(dt, channel_id, self._unsilence_wrapper(channel))
+
     def cog_unload(self) -> None:
-        """Send alert with silenced channels and cancel scheduled tasks on unload."""
+        """Cancel scheduled tasks."""
         self.scheduler.cancel_all()
-        if self.muted_channel_perms:
-            channels_string = ''.join(channel.mention for channel in self.muted_channel_perms)
-            message = f"<@&{Roles.moderators}> channels left silenced on cog unload: {channels_string}"
-            asyncio.create_task(self._mod_alerts_channel.send(message))
 
     # This cannot be static (must have a __func__ attribute).
     def cog_check(self, ctx: Context) -> bool: