Merge branch 'master' into bug/mod/bot-2a/webhook-clyde

13 files changed, 285 insertions, 100 deletions

diff --git a/Pipfile b/Pipfile
index b42ca6d58..33be99587 100644
--- a/Pipfile
+++ b/Pipfile
@@ -50,4 +50,5 @@ precommit = "pre-commit install"
 build = "docker build -t pythondiscord/bot:latest -f Dockerfile ."
 push = "docker push pythondiscord/bot:latest"
 test = "coverage run -m unittest"
+html = "coverage html"
 report = "coverage report"
diff --git a/bot/cogs/filtering.py b/bot/cogs/filtering.py
index 4ebc831e1..76ea68660 100644
--- a/bot/cogs/filtering.py
+++ b/bot/cogs/filtering.py
@@ -2,11 +2,12 @@ import asyncio
 import logging
 import re
 from datetime import datetime, timedelta
-from typing import List, Optional, Union
+from typing import List, Mapping, Optional, Union
 
+import dateutil
 import discord.errors
 from dateutil.relativedelta import relativedelta
-from discord import Colour, Member, Message, TextChannel
+from discord import Colour, HTTPException, Member, Message, NotFound, TextChannel
 from discord.ext.commands import Cog
 from discord.utils import escape_markdown
 
@@ -17,6 +18,8 @@ from bot.constants import (
     Filter, Icons, URLs
 )
 from bot.utils.redis_cache import RedisCache
+from bot.utils.scheduling import Scheduler
+from bot.utils.time import wait_until
 
 log = logging.getLogger(__name__)
 
@@ -54,7 +57,10 @@ def expand_spoilers(text: str) -> str:
     )
 
 
-class Filtering(Cog):
+OFFENSIVE_MSG_DELETE_TIME = timedelta(days=Filter.offensive_msg_delete_days)
+
+
+class Filtering(Cog, Scheduler):
     """Filtering out invites, blacklisting domains, and warning us of certain regular expressions."""
 
     # Redis cache mapping a user ID to the last timestamp a bad nickname alert was sent
@@ -62,6 +68,8 @@ class Filtering(Cog):
 
     def __init__(self, bot: Bot):
         self.bot = bot
+        super().__init__()
+
         self.name_lock = asyncio.Lock()
 
         staff_mistake_str = "If you believe this was a mistake, please let staff know!"
@@ -75,7 +83,8 @@ class Filtering(Cog):
                 "notification_msg": (
                     "Your post has been removed for abusing Unicode character rendering (aka Zalgo text). "
                     f"{staff_mistake_str}"
-                )
+                ),
+                "schedule_deletion": False
             },
             "filter_invites": {
                 "enabled": Filter.filter_invites,
@@ -86,7 +95,8 @@ class Filtering(Cog):
                 "notification_msg": (
                     f"Per Rule 6, your invite link has been removed. {staff_mistake_str}\n\n"
                     r"Our server rules can be found here: <https://pythondiscord.com/pages/rules>"
-                )
+                ),
+                "schedule_deletion": False
             },
             "filter_domains": {
                 "enabled": Filter.filter_domains,
@@ -96,22 +106,27 @@ class Filtering(Cog):
                 "user_notification": Filter.notify_user_domains,
                 "notification_msg": (
                     f"Your URL has been removed because it matched a blacklisted domain. {staff_mistake_str}"
-                )
+                ),
+                "schedule_deletion": False
             },
             "watch_regex": {
                 "enabled": Filter.watch_regex,
                 "function": self._has_watch_regex_match,
                 "type": "watchlist",
                 "content_only": True,
+                "schedule_deletion": True
             },
             "watch_rich_embeds": {
                 "enabled": Filter.watch_rich_embeds,
                 "function": self._has_rich_embed,
                 "type": "watchlist",
                 "content_only": False,
-            },
+                "schedule_deletion": False
+            }
         }
 
+        self.bot.loop.create_task(self.reschedule_offensive_msg_deletion())
+
     @property
     def mod_log(self) -> ModLog:
         """Get currently loaded ModLog cog instance."""
@@ -242,6 +257,20 @@ class Filtering(Cog):
                             if _filter["user_notification"]:
                                 await self.notify_member(msg.author, _filter["notification_msg"], msg.channel)
 
+                        # If the message is classed as offensive, we store it in the site db and
+                        # it will be deleted it after one week.
+                        if _filter["schedule_deletion"] and not is_private:
+                            delete_date = (msg.created_at + OFFENSIVE_MSG_DELETE_TIME).isoformat()
+                            data = {
+                                'id': msg.id,
+                                'channel_id': msg.channel.id,
+                                'delete_date': delete_date
+                            }
+
+                            await self.bot.api_client.post('bot/offensive-messages', json=data)
+                            self.schedule_task(msg.id, data)
+                            log.trace(f"Offensive message {msg.id} will be deleted on {delete_date}")
+
                         if is_private:
                             channel_str = "via DM"
                         else:
@@ -359,7 +388,7 @@ class Filtering(Cog):
 
         Attempts to catch some of common ways to try to cheat the system.
         """
-        # Remove backslashes to prevent escape character aroundfuckery like
+        # Remove backslashes to prevent escape character around fuckery like
         # discord\.gg/gdudes-pony-farm
         text = text.replace("\\", "")
 
@@ -428,6 +457,46 @@ class Filtering(Cog):
         except discord.errors.Forbidden:
             await channel.send(f"{filtered_member.mention} {reason}")
 
+    async def _scheduled_task(self, msg: dict) -> None:
+        """Delete an offensive message once its deletion date is reached."""
+        delete_at = dateutil.parser.isoparse(msg['delete_date']).replace(tzinfo=None)
+
+        await wait_until(delete_at)
+        await self.delete_offensive_msg(msg)
+
+    async def reschedule_offensive_msg_deletion(self) -> None:
+        """Get all the pending message deletion from the API and reschedule them."""
+        await self.bot.wait_until_ready()
+        response = await self.bot.api_client.get('bot/offensive-messages',)
+
+        now = datetime.utcnow()
+
+        for msg in response:
+            delete_at = dateutil.parser.isoparse(msg['delete_date']).replace(tzinfo=None)
+
+            if delete_at < now:
+                await self.delete_offensive_msg(msg)
+            else:
+                self.schedule_task(msg['id'], msg)
+
+    async def delete_offensive_msg(self, msg: Mapping[str, str]) -> None:
+        """Delete an offensive message, and then delete it from the db."""
+        try:
+            channel = self.bot.get_channel(msg['channel_id'])
+            if channel:
+                msg_obj = await channel.fetch_message(msg['id'])
+                await msg_obj.delete()
+        except NotFound:
+            log.info(
+                f"Tried to delete message {msg['id']}, but the message can't be found "
+                f"(it has been probably already deleted)."
+            )
+        except HTTPException as e:
+            log.warning(f"Failed to delete message {msg['id']}: status {e.status}")
+
+        await self.bot.api_client.delete(f'bot/offensive-messages/{msg["id"]}')
+        log.info(f"Deleted the offensive message with id {msg['id']}.")
+
 
 def setup(bot: Bot) -> None:
     """Load the Filtering cog."""
diff --git a/bot/cogs/help_channels.py b/bot/cogs/help_channels.py
index 6ff285c37..187adfe51 100644
--- a/bot/cogs/help_channels.py
+++ b/bot/cogs/help_channels.py
@@ -5,8 +5,7 @@ import logging
 import random
 import typing as t
 from collections import deque
-from contextlib import suppress
-from datetime import datetime
+from datetime import datetime, timedelta, timezone
 from pathlib import Path
 
 import discord
@@ -15,6 +14,7 @@ from discord.ext import commands
 
 from bot import constants
 from bot.bot import Bot
+from bot.utils import RedisCache
 from bot.utils.checks import with_role_check
 from bot.utils.scheduling import Scheduler
 
@@ -99,13 +99,24 @@ class HelpChannels(Scheduler, commands.Cog):
     Help channels are named after the chemical elements in `bot/resources/elements.json`.
     """
 
+    # This cache tracks which channels are claimed by which members.
+    # RedisCache[discord.TextChannel.id, t.Union[discord.User.id, discord.Member.id]]
+    help_channel_claimants = RedisCache()
+
+    # This cache maps a help channel to whether it has had any
+    # activity other than the original claimant. True being no other
+    # activity and False being other activity.
+    # RedisCache[discord.TextChannel.id, bool]
+    unanswered = RedisCache()
+
+    # This dictionary maps a help channel to the time it was claimed
+    # RedisCache[discord.TextChannel.id, UtcPosixTimestamp]
+    claim_times = RedisCache()
+
     def __init__(self, bot: Bot):
         super().__init__()
 
         self.bot = bot
-        self.help_channel_claimants: (
-            t.Dict[discord.TextChannel, t.Union[discord.Member, discord.User]]
-        ) = {}
 
         # Categories
         self.available_category: discord.CategoryChannel = None
@@ -125,16 +136,6 @@ class HelpChannels(Scheduler, commands.Cog):
         self.on_message_lock = asyncio.Lock()
         self.init_task = self.bot.loop.create_task(self.init_cog())
 
-        # Stats
-
-        # This dictionary maps a help channel to the time it was claimed
-        self.claim_times: t.Dict[int, datetime] = {}
-
-        # This dictionary maps a help channel to whether it has had any
-        # activity other than the original claimant. True being no other
-        # activity and False being other activity.
-        self.unanswered: t.Dict[int, bool] = {}
-
     def cog_unload(self) -> None:
         """Cancel the init task and scheduled tasks when the cog unloads."""
         log.trace("Cog unload: cancelling the init_cog task")
@@ -197,7 +198,7 @@ class HelpChannels(Scheduler, commands.Cog):
 
     async def dormant_check(self, ctx: commands.Context) -> bool:
         """Return True if the user is the help channel claimant or passes the role check."""
-        if self.help_channel_claimants.get(ctx.channel) == ctx.author:
+        if await self.help_channel_claimants.get(ctx.channel.id) == ctx.author.id:
             log.trace(f"{ctx.author} is the help channel claimant, passing the check for dormant.")
             self.bot.stats.incr("help.dormant_invoke.claimant")
             return True
@@ -222,10 +223,11 @@ class HelpChannels(Scheduler, commands.Cog):
         log.trace("close command invoked; checking if the channel is in-use.")
         if ctx.channel.category == self.in_use_category:
             if await self.dormant_check(ctx):
-                with suppress(KeyError):
-                    del self.help_channel_claimants[ctx.channel]
 
+                # Remove the claimant and the cooldown role
+                await self.help_channel_claimants.delete(ctx.channel.id)
                 await self.remove_cooldown_role(ctx.author)
+
                 # Ignore missing task when cooldown has passed but the channel still isn't dormant.
                 self.cancel_task(ctx.author.id, ignore_missing=True)
 
@@ -284,6 +286,15 @@ class HelpChannels(Scheduler, commands.Cog):
             if channel.category_id == category.id and not self.is_excluded_channel(channel):
                 yield channel
 
+    async def get_in_use_time(self, channel_id: int) -> t.Optional[timedelta]:
+        """Return the duration `channel_id` has been in use. Return None if it's not in use."""
+        log.trace(f"Calculating in use time for channel {channel_id}.")
+
+        claimed_timestamp = await self.claim_times.get(channel_id)
+        if claimed_timestamp:
+            claimed = datetime.utcfromtimestamp(claimed_timestamp)
+            return datetime.utcnow() - claimed
+
     @staticmethod
     def get_names() -> t.List[str]:
         """
@@ -386,7 +397,7 @@ class HelpChannels(Scheduler, commands.Cog):
 
         log.trace("Initialising the cog.")
         await self.init_categories()
-        await self.reset_send_permissions()
+        await self.check_cooldowns()
 
         self.channel_queue = self.create_channel_queue()
         self.name_queue = self.create_name_queue()
@@ -546,19 +557,17 @@ class HelpChannels(Scheduler, commands.Cog):
 
         self.bot.stats.incr(f"help.dormant_calls.{caller}")
 
-        if channel.id in self.claim_times:
-            claimed = self.claim_times[channel.id]
-            in_use_time = datetime.now() - claimed
+        in_use_time = await self.get_in_use_time(channel.id)
+        if in_use_time:
             self.bot.stats.timing("help.in_use_time", in_use_time)
 
-        if channel.id in self.unanswered:
-            if self.unanswered[channel.id]:
-                self.bot.stats.incr("help.sessions.unanswered")
-            else:
-                self.bot.stats.incr("help.sessions.answered")
+        unanswered = await self.unanswered.get(channel.id)
+        if unanswered:
+            self.bot.stats.incr("help.sessions.unanswered")
+        elif unanswered is not None:
+            self.bot.stats.incr("help.sessions.answered")
 
         log.trace(f"Position of #{channel} ({channel.id}) is actually {channel.position}.")
-
         log.trace(f"Sending dormant message for #{channel} ({channel.id}).")
         embed = discord.Embed(description=DORMANT_MSG)
         await channel.send(embed=embed)
@@ -637,17 +646,17 @@ class HelpChannels(Scheduler, commands.Cog):
         if self.is_in_category(channel, constants.Categories.help_in_use):
             log.trace(f"Checking if #{channel} ({channel.id}) has been answered.")
 
-            # Check if there is an entry in unanswered (does not persist across restarts)
-            if channel.id in self.unanswered:
-                claimant = self.help_channel_claimants.get(channel)
-                if not claimant:
-                    # The mapping for this channel was lost, we can't do anything.
+            # Check if there is an entry in unanswered
+            if await self.unanswered.contains(channel.id):
+                claimant_id = await self.help_channel_claimants.get(channel.id)
+                if not claimant_id:
+                    # The mapping for this channel doesn't exist, we can't do anything.
                     return
 
                 # Check the message did not come from the claimant
-                if claimant.id != message.author.id:
+                if claimant_id != message.author.id:
                     # Mark the channel as answered
-                    self.unanswered[channel.id] = False
+                    await self.unanswered.set(channel.id, False)
 
     @commands.Cog.listener()
     async def on_message(self, message: discord.Message) -> None:
@@ -680,12 +689,15 @@ class HelpChannels(Scheduler, commands.Cog):
             await self.move_to_in_use(channel)
             await self.revoke_send_permissions(message.author)
             # Add user with channel for dormant check.
-            self.help_channel_claimants[channel] = message.author
+            await self.help_channel_claimants.set(channel.id, message.author.id)
 
             self.bot.stats.incr("help.claimed")
 
-            self.claim_times[channel.id] = datetime.now()
-            self.unanswered[channel.id] = True
+            # Must use a timezone-aware datetime to ensure a correct POSIX timestamp.
+            timestamp = datetime.now(timezone.utc).timestamp()
+            await self.claim_times.set(channel.id, timestamp)
+
+            await self.unanswered.set(channel.id, True)
 
             log.trace(f"Releasing on_message lock for {message.id}.")
 
@@ -720,15 +732,28 @@ class HelpChannels(Scheduler, commands.Cog):
         msg = await self.get_last_message(channel)
         return self.match_bot_embed(msg, AVAILABLE_MSG)
 
-    async def reset_send_permissions(self) -> None:
-        """Reset send permissions in the Available category for claimants."""
-        log.trace("Resetting send permissions in the Available category.")
+    async def check_cooldowns(self) -> None:
+        """Remove expired cooldowns and re-schedule active ones."""
+        log.trace("Checking all cooldowns to remove or re-schedule them.")
         guild = self.bot.get_guild(constants.Guild.id)
+        cooldown = constants.HelpChannels.claim_minutes * 60
+
+        for channel_id, member_id in await self.help_channel_claimants.items():
+            member = guild.get_member(member_id)
+            if not member:
+                continue  # Member probably left the guild.
+
+            in_use_time = await self.get_in_use_time(channel_id)
 
-        # TODO: replace with a persistent cache cause checking every member is quite slow
-        for member in guild.members:
-            if self.is_claimant(member):
+            if not in_use_time or in_use_time.seconds > cooldown:
+                # Remove the role if no claim time could be retrieved or if the cooldown expired.
+                # Since the channel is in the claimants cache, it is definitely strange for a time
+                # to not exist. However, it isn't a reason to keep the user stuck with a cooldown.
                 await self.remove_cooldown_role(member)
+            else:
+                # The member is still on a cooldown; re-schedule it for the remaining time.
+                remaining = cooldown - in_use_time.seconds
+                await self.schedule_cooldown_expiration(member, remaining)
 
     async def add_cooldown_role(self, member: discord.Member) -> None:
         """Add the help cooldown role to `member`."""
@@ -781,11 +806,14 @@ class HelpChannels(Scheduler, commands.Cog):
         # Would mean the user somehow bypassed the lack of permissions (e.g. user is guild owner).
         self.cancel_task(member.id, ignore_missing=True)
 
-        timeout = constants.HelpChannels.claim_minutes * 60
-        callback = self.remove_cooldown_role(member)
+        await self.schedule_cooldown_expiration(member, constants.HelpChannels.claim_minutes * 60)
 
-        log.trace(f"Scheduling {member}'s ({member.id}) send message permissions to be reinstated.")
-        self.schedule_task(member.id, TaskData(timeout, callback))
+    async def schedule_cooldown_expiration(self, member: discord.Member, seconds: int) -> None:
+        """Schedule the cooldown role for `member` to be removed after a duration of `seconds`."""
+        log.trace(f"Scheduling removal of {member}'s ({member.id}) cooldown.")
+
+        callback = self.remove_cooldown_role(member)
+        self.schedule_task(member.id, TaskData(seconds, callback))
 
     async def send_available_message(self, channel: discord.TextChannel) -> None:
         """Send the available message by editing a dormant message or sending a new message."""
diff --git a/bot/cogs/moderation/infractions.py b/bot/cogs/moderation/infractions.py
index 5bfaad796..3b28526b2 100644
--- a/bot/cogs/moderation/infractions.py
+++ b/bot/cogs/moderation/infractions.py
@@ -53,7 +53,7 @@ class Infractions(InfractionScheduler, commands.Cog):
     # region: Permanent infractions
 
     @command()
-    async def warn(self, ctx: Context, user: Member, *, reason: str = None) -> None:
+    async def warn(self, ctx: Context, user: Member, *, reason: t.Optional[str] = None) -> None:
         """Warn a user for the given reason."""
         infraction = await utils.post_infraction(ctx, user, "warning", reason, active=False)
         if infraction is None:
@@ -62,12 +62,12 @@ class Infractions(InfractionScheduler, commands.Cog):
         await self.apply_infraction(ctx, infraction, user)
 
     @command()
-    async def kick(self, ctx: Context, user: Member, *, reason: str = None) -> None:
+    async def kick(self, ctx: Context, user: Member, *, reason: t.Optional[str] = None) -> None:
         """Kick a user for the given reason."""
         await self.apply_kick(ctx, user, reason, active=False)
 
     @command()
-    async def ban(self, ctx: Context, user: FetchedMember, *, reason: str = None) -> None:
+    async def ban(self, ctx: Context, user: FetchedMember, *, reason: t.Optional[str] = None) -> None:
         """Permanently ban a user for the given reason and stop watching them with Big Brother."""
         await self.apply_ban(ctx, user, reason)
 
@@ -75,7 +75,7 @@ class Infractions(InfractionScheduler, commands.Cog):
     # region: Temporary infractions
 
     @command(aliases=["mute"])
-    async def tempmute(self, ctx: Context, user: Member, duration: Expiry, *, reason: str = None) -> None:
+    async def tempmute(self, ctx: Context, user: Member, duration: Expiry, *, reason: t.Optional[str] = None) -> None:
         """
         Temporarily mute a user for the given reason and duration.
 
@@ -94,7 +94,14 @@ class Infractions(InfractionScheduler, commands.Cog):
         await self.apply_mute(ctx, user, reason, expires_at=duration)
 
     @command()
-    async def tempban(self, ctx: Context, user: FetchedMember, duration: Expiry, *, reason: str = None) -> None:
+    async def tempban(
+        self,
+        ctx: Context,
+        user: FetchedMember,
+        duration: Expiry,
+        *,
+        reason: t.Optional[str] = None
+    ) -> None:
         """
         Temporarily ban a user for the given reason and duration.
 
@@ -116,7 +123,7 @@ class Infractions(InfractionScheduler, commands.Cog):
     # region: Permanent shadow infractions
 
     @command(hidden=True)
-    async def note(self, ctx: Context, user: FetchedMember, *, reason: str = None) -> None:
+    async def note(self, ctx: Context, user: FetchedMember, *, reason: t.Optional[str] = None) -> None:
         """Create a private note for a user with the given reason without notifying the user."""
         infraction = await utils.post_infraction(ctx, user, "note", reason, hidden=True, active=False)
         if infraction is None:
@@ -125,12 +132,12 @@ class Infractions(InfractionScheduler, commands.Cog):
         await self.apply_infraction(ctx, infraction, user)
 
     @command(hidden=True, aliases=['shadowkick', 'skick'])
-    async def shadow_kick(self, ctx: Context, user: Member, *, reason: str = None) -> None:
+    async def shadow_kick(self, ctx: Context, user: Member, *, reason: t.Optional[str] = None) -> None:
         """Kick a user for the given reason without notifying the user."""
         await self.apply_kick(ctx, user, reason, hidden=True, active=False)
 
     @command(hidden=True, aliases=['shadowban', 'sban'])
-    async def shadow_ban(self, ctx: Context, user: FetchedMember, *, reason: str = None) -> None:
+    async def shadow_ban(self, ctx: Context, user: FetchedMember, *, reason: t.Optional[str] = None) -> None:
         """Permanently ban a user for the given reason without notifying the user."""
         await self.apply_ban(ctx, user, reason, hidden=True)
 
@@ -138,7 +145,13 @@ class Infractions(InfractionScheduler, commands.Cog):
     # region: Temporary shadow infractions
 
     @command(hidden=True, aliases=["shadowtempmute, stempmute", "shadowmute", "smute"])
-    async def shadow_tempmute(self, ctx: Context, user: Member, duration: Expiry, *, reason: str = None) -> None:
+    async def shadow_tempmute(
+        self, ctx: Context,
+        user: Member,
+        duration: Expiry,
+        *,
+        reason: t.Optional[str] = None
+    ) -> None:
         """
         Temporarily mute a user for the given reason and duration without notifying the user.
 
@@ -163,7 +176,7 @@ class Infractions(InfractionScheduler, commands.Cog):
         user: FetchedMember,
         duration: Expiry,
         *,
-        reason: str = None
+        reason: t.Optional[str] = None
     ) -> None:
         """
         Temporarily ban a user for the given reason and duration without notifying the user.
@@ -198,7 +211,7 @@ class Infractions(InfractionScheduler, commands.Cog):
     # endregion
     # region: Base apply functions
 
-    async def apply_mute(self, ctx: Context, user: Member, reason: str, **kwargs) -> None:
+    async def apply_mute(self, ctx: Context, user: Member, reason: t.Optional[str], **kwargs) -> None:
         """Apply a mute infraction with kwargs passed to `post_infraction`."""
         if await utils.get_active_infraction(ctx, user, "mute"):
             return
@@ -218,7 +231,7 @@ class Infractions(InfractionScheduler, commands.Cog):
         await self.apply_infraction(ctx, infraction, user, action())
 
     @respect_role_hierarchy()
-    async def apply_kick(self, ctx: Context, user: Member, reason: str, **kwargs) -> None:
+    async def apply_kick(self, ctx: Context, user: Member, reason: t.Optional[str], **kwargs) -> None:
         """Apply a kick infraction with kwargs passed to `post_infraction`."""
         infraction = await utils.post_infraction(ctx, user, "kick", reason, active=False, **kwargs)
         if infraction is None:
@@ -226,11 +239,14 @@ class Infractions(InfractionScheduler, commands.Cog):
 
         self.mod_log.ignore(Event.member_remove, user.id)
 
-        action = user.kick(reason=textwrap.shorten(reason, width=512, placeholder="..."))
+        if reason:
+            reason = textwrap.shorten(reason, width=512, placeholder="...")
+
+        action = user.kick(reason=reason)
         await self.apply_infraction(ctx, infraction, user, action)
 
     @respect_role_hierarchy()
-    async def apply_ban(self, ctx: Context, user: UserSnowflake, reason: str, **kwargs) -> None:
+    async def apply_ban(self, ctx: Context, user: UserSnowflake, reason: t.Optional[str], **kwargs) -> None:
         """
         Apply a ban infraction with kwargs passed to `post_infraction`.
 
@@ -259,9 +275,10 @@ class Infractions(InfractionScheduler, commands.Cog):
 
         self.mod_log.ignore(Event.member_remove, user.id)
 
-        truncated_reason = textwrap.shorten(reason, width=512, placeholder="...")
+        if reason:
+            reason = textwrap.shorten(reason, width=512, placeholder="...")
 
-        action = ctx.guild.ban(user, reason=truncated_reason, delete_message_days=0)
+        action = ctx.guild.ban(user, reason=reason, delete_message_days=0)
         await self.apply_infraction(ctx, infraction, user, action)
 
         if infraction.get('expires_at') is not None:
@@ -281,7 +298,7 @@ class Infractions(InfractionScheduler, commands.Cog):
     # endregion
     # region: Base pardon functions
 
-    async def pardon_mute(self, user_id: int, guild: discord.Guild, reason: str) -> t.Dict[str, str]:
+    async def pardon_mute(self, user_id: int, guild: discord.Guild, reason: t.Optional[str]) -> t.Dict[str, str]:
         """Remove a user's muted role, DM them a notification, and return a log dict."""
         user = guild.get_member(user_id)
         log_text = {}
@@ -307,7 +324,7 @@ class Infractions(InfractionScheduler, commands.Cog):
 
         return log_text
 
-    async def pardon_ban(self, user_id: int, guild: discord.Guild, reason: str) -> t.Dict[str, str]:
+    async def pardon_ban(self, user_id: int, guild: discord.Guild, reason: t.Optional[str]) -> t.Dict[str, str]:
         """Remove a user's ban on the Discord guild and return a log dict."""
         user = discord.Object(user_id)
         log_text = {}
diff --git a/bot/cogs/moderation/scheduler.py b/bot/cogs/moderation/scheduler.py
index b03d89537..d75a72ddb 100644
--- a/bot/cogs/moderation/scheduler.py
+++ b/bot/cogs/moderation/scheduler.py
@@ -127,18 +127,17 @@ class InfractionScheduler(Scheduler):
                     dm_result = ":incoming_envelope: "
                     dm_log_text = "\nDM: Sent"
 
+        end_msg = ""
         if infraction["actor"] == self.bot.user.id:
             log.trace(
                 f"Infraction #{id_} actor is bot; including the reason in the confirmation message."
             )
-
-            end_msg = f" (reason: {textwrap.shorten(reason, width=1500, placeholder='...')})"
+            if reason:
+                end_msg = f" (reason: {textwrap.shorten(reason, width=1500, placeholder='...')})"
         elif ctx.channel.id not in STAFF_CHANNELS:
             log.trace(
                 f"Infraction #{id_} context is not in a staff channel; omitting infraction count."
             )
-
-            end_msg = ""
         else:
             log.trace(f"Fetching total infraction count for {user}.")
 
diff --git a/bot/cogs/token_remover.py b/bot/cogs/token_remover.py
index d55e079e9..ef979f222 100644
--- a/bot/cogs/token_remover.py
+++ b/bot/cogs/token_remover.py
@@ -4,7 +4,7 @@ import logging
 import re
 import typing as t
 
-from discord import Colour, Message
+from discord import Colour, Message, NotFound
 from discord.ext.commands import Cog
 
 from bot import utils
@@ -63,6 +63,10 @@ class TokenRemover(Cog):
 
         See: https://discordapp.com/developers/docs/reference#snowflakes
         """
+        # Ignore DMs; can't delete messages in there anyway.
+        if not msg.guild or msg.author.bot:
+            return
+
         found_token = self.find_token_in_message(msg)
         if found_token:
             await self.take_action(msg, found_token)
@@ -79,7 +83,13 @@ class TokenRemover(Cog):
     async def take_action(self, msg: Message, found_token: Token) -> None:
         """Remove the `msg` containing the `found_token` and send a mod log message."""
         self.mod_log.ignore(Event.message_delete, msg.id)
-        await msg.delete()
+
+        try:
+            await msg.delete()
+        except NotFound:
+            log.debug(f"Failed to remove token in message {msg.id}: message already deleted.")
+            return
+
         await msg.channel.send(DELETION_MESSAGE_TEMPLATE.format(mention=msg.author.mention))
 
         log_message = self.format_log_message(msg, found_token)
@@ -112,9 +122,6 @@ class TokenRemover(Cog):
     @classmethod
     def find_token_in_message(cls, msg: Message) -> t.Optional[Token]:
         """Return a seemingly valid token found in `msg` or `None` if no token is found."""
-        if msg.author.bot:
-            return
-
         # Use finditer rather than search to guard against method calls prematurely returning the
         # token check (e.g. `message.channel.send` also matches our token pattern)
         for match in TOKEN_RE.finditer(msg.content):
diff --git a/bot/cogs/webhook_remover.py b/bot/cogs/webhook_remover.py
index 1b5c3f821..543869215 100644
--- a/bot/cogs/webhook_remover.py
+++ b/bot/cogs/webhook_remover.py
@@ -1,7 +1,7 @@
 import logging
 import re
 
-from discord import Colour, Message
+from discord import Colour, Message, NotFound
 from discord.ext.commands import Cog
 
 from bot.bot import Bot
@@ -35,7 +35,13 @@ class WebhookRemover(Cog):
         """Delete `msg` and send a warning that it contained the Discord webhook `redacted_url`."""
         # Don't log this, due internal delete, not by user. Will make different entry.
         self.mod_log.ignore(Event.message_delete, msg.id)
-        await msg.delete()
+
+        try:
+            await msg.delete()
+        except NotFound:
+            log.debug(f"Failed to remove webhook in message {msg.id}: message already deleted.")
+            return
+
         await msg.channel.send(ALERT_MESSAGE_TEMPLATE.format(user=msg.author.mention))
 
         message = (
@@ -59,6 +65,10 @@ class WebhookRemover(Cog):
     @Cog.listener()
     async def on_message(self, msg: Message) -> None:
         """Check if a Discord webhook URL is in `message`."""
+        # Ignore DMs; can't delete messages in there anyway.
+        if not msg.guild or msg.author.bot:
+            return
+
         matches = WEBHOOK_URL_RE.search(msg.content)
         if matches:
             await self.delete_and_respond(msg, matches[1] + "xxx")
diff --git a/bot/constants.py b/bot/constants.py
index 470221369..a1b392c82 100644
--- a/bot/constants.py
+++ b/bot/constants.py
@@ -226,6 +226,7 @@ class Filter(metaclass=YAMLGetter):
     notify_user_domains: bool
 
     ping_everyone: bool
+    offensive_msg_delete_days: int
     guild_invite_whitelist: List[int]
     domain_blacklist: List[str]
     word_watchlist: List[str]
diff --git a/bot/resources/tags/customcooldown.md b/bot/resources/tags/customcooldown.md
new file mode 100644
index 000000000..ac7e70aee
--- /dev/null
+++ b/bot/resources/tags/customcooldown.md
@@ -0,0 +1,20 @@
+**Cooldowns in discord.py**
+
+Cooldowns can be used in discord.py to rate-limit. In this example, we're using it in an on_message.
+
+```python
+from discord.ext import commands
+
+message_cooldown = commands.CooldownMapping.from_cooldown(1.0, 60.0, commands.BucketType.user)
+
[email protected]
+async def on_message(message):
+    bucket = message_cooldown.get_bucket(message)
+    retry_after = bucket.update_rate_limit()
+    if retry_after:
+        await message.channel.send(f"Slow down! Try again in {retry_after} seconds.")
+    else:
+        await message.channel.send("Not ratelimited!")
+```
+
+`from_cooldown` takes the amount of `update_rate_limit()`s needed to trigger the cooldown, the time in which the cooldown is triggered, and a [`BucketType`](https://discordpy.readthedocs.io/en/latest/ext/commands/api.html#discord.discord.ext.commands.BucketType).
diff --git a/bot/utils/redis_cache.py b/bot/utils/redis_cache.py
index 354e987b9..58cfe1df5 100644
--- a/bot/utils/redis_cache.py
+++ b/bot/utils/redis_cache.py
@@ -11,7 +11,7 @@ log = logging.getLogger(__name__)
 
 # Type aliases
 RedisKeyType = Union[str, int]
-RedisValueType = Union[str, int, float]
+RedisValueType = Union[str, int, float, bool]
 RedisKeyOrValue = Union[RedisKeyType, RedisValueType]
 
 # Prefix tuples
@@ -20,6 +20,7 @@ _VALUE_PREFIXES = (
     ("f|", float),
     ("i|", int),
     ("s|", str),
+    ("b|", bool),
 )
 _KEY_PREFIXES = (
     ("i|", int),
@@ -47,8 +48,8 @@ class RedisCache:
     behaves, and should be familiar to Python users. The biggest difference is that
     all the public methods in this class are coroutines, and must be awaited.
 
-    Because of limitations in Redis, this cache will only accept strings, integers and
-    floats both for keys and values.
+    Because of limitations in Redis, this cache will only accept strings and integers for keys,
+    and strings, integers, floats and booleans for values.
 
     Please note that this class MUST be created as a class attribute, and that that class
     must also contain an attribute with an instance of our Bot. See `__get__` and `__set_name__`
@@ -108,8 +109,15 @@ class RedisCache:
     def _to_typestring(key_or_value: RedisKeyOrValue, prefixes: _PrefixTuple) -> str:
         """Turn a valid Redis type into a typestring."""
         for prefix, _type in prefixes:
-            if isinstance(key_or_value, _type):
+            # Convert bools into integers before storing them.
+            if type(key_or_value) is bool:
+                bool_int = int(key_or_value)
+                return f"{prefix}{bool_int}"
+
+            # isinstance is a bad idea here, because isintance(False, int) == True.
+            if type(key_or_value) is _type:
                 return f"{prefix}{key_or_value}"
+
         raise TypeError(f"RedisCache._to_typestring only supports the following: {prefixes}.")
 
     @staticmethod
@@ -122,6 +130,13 @@ class RedisCache:
         # Now we convert our unicode string back into the type it originally was.
         for prefix, _type in prefixes:
             if key_or_value.startswith(prefix):
+
+                # For booleans, we need special handling because bool("False") is True.
+                if prefix == "b|":
+                    value = key_or_value[len(prefix):]
+                    return bool(int(value))
+
+                # Otherwise we can just convert normally.
                 return _type(key_or_value[len(prefix):])
         raise TypeError(f"RedisCache._from_typestring only supports the following: {prefixes}.")
 
diff --git a/config-default.yml b/config-default.yml
index aff5fb2e1..64c4e715b 100644
--- a/config-default.yml
+++ b/config-default.yml
@@ -269,7 +269,8 @@ filter:
     notify_user_domains:     false
 
     # Filter configuration
-    ping_everyone: true  # Ping @everyone when we send a mod-alert?
+    ping_everyone:             true  # Ping @everyone when we send a mod-alert?
+    offensive_msg_delete_days: 7     # How many days before deleting an offensive message?
 
     guild_invite_whitelist:
         - 280033776820813825  # Functional Programming
@@ -331,6 +332,7 @@ filter:
         - ssteam.site
         - steamwalletgift.com
         - discord.gift
+        - lmgtfy.com
 
     word_watchlist:
         - goo+ks*
diff --git a/tests/bot/cogs/test_token_remover.py b/tests/bot/cogs/test_token_remover.py
index a10124d2d..3349caa73 100644
--- a/tests/bot/cogs/test_token_remover.py
+++ b/tests/bot/cogs/test_token_remover.py
@@ -3,7 +3,7 @@ from re import Match
 from unittest import mock
 from unittest.mock import MagicMock
 
-from discord import Colour
+from discord import Colour, NotFound
 
 from bot import constants
 from bot.cogs import token_remover
@@ -121,15 +121,16 @@ class TokenRemoverTests(unittest.IsolatedAsyncioTestCase):
         find_token_in_message.assert_called_once_with(self.msg)
         take_action.assert_not_awaited()
 
-    @autospec("bot.cogs.token_remover", "TOKEN_RE")
-    def test_find_token_ignores_bot_messages(self, token_re):
-        """The token finder should ignore messages authored by bots."""
-        self.msg.author.bot = True
+    @autospec(TokenRemover, "find_token_in_message")
+    async def test_on_message_ignores_dms_bots(self, find_token_in_message):
+        """Shouldn't parse a message if it is a DM or authored by a bot."""
+        cog = TokenRemover(self.bot)
+        dm_msg = MockMessage(guild=None)
+        bot_msg = MockMessage(author=MagicMock(bot=True))
 
-        return_value = TokenRemover.find_token_in_message(self.msg)
-
-        self.assertIsNone(return_value)
-        token_re.finditer.assert_not_called()
+        for msg in (dm_msg, bot_msg):
+            await cog.on_message(msg)
+            find_token_in_message.assert_not_called()
 
     @autospec("bot.cogs.token_remover", "TOKEN_RE")
     def test_find_token_no_matches(self, token_re):
@@ -281,6 +282,19 @@ class TokenRemoverTests(unittest.IsolatedAsyncioTestCase):
             channel_id=constants.Channels.mod_alerts
         )
 
+    @mock.patch.object(TokenRemover, "mod_log", new_callable=mock.PropertyMock)
+    async def test_take_action_delete_failure(self, mod_log_property):
+        """Shouldn't send any messages if the token message can't be deleted."""
+        cog = TokenRemover(self.bot)
+        mod_log_property.return_value = mock.create_autospec(ModLog, spec_set=True, instance=True)
+        self.msg.delete.side_effect = NotFound(MagicMock(), MagicMock())
+
+        token = mock.create_autospec(Token, spec_set=True, instance=True)
+        await cog.take_action(self.msg, token)
+
+        self.msg.delete.assert_called_once_with()
+        self.msg.channel.send.assert_not_awaited()
+
 
 class TokenRemoverExtensionTests(unittest.TestCase):
     """Tests for the token_remover extension."""
diff --git a/tests/bot/utils/test_redis_cache.py b/tests/bot/utils/test_redis_cache.py
index e5d6e4078..a2f0fe55d 100644
--- a/tests/bot/utils/test_redis_cache.py
+++ b/tests/bot/utils/test_redis_cache.py
@@ -49,7 +49,9 @@ class RedisCacheTests(unittest.IsolatedAsyncioTestCase):
         test_cases = (
             ('favorite_fruit', 'melon'),
             ('favorite_number', 86),
-            ('favorite_fraction', 86.54)
+            ('favorite_fraction', 86.54),
+            ('favorite_boolean', False),
+            ('other_boolean', True),
         )
 
         # Test that we can get and set different types.