Add a new Cog for Pinned Messages which keeps reminders as the latest…

… message in a channel (#113)

cogs/__init__.py

@@ -3,12 +3,14 @@
 from . import inclusive_language
 from . import mentor_requests
 from . import mod_message
+from . import pinned_message
 from . import streaming_events
 from . import track_react
 
 CloseSupportThread = close_support.CloseSupportThread
 InclusiveLanguage = inclusive_language.InclusiveLanguage
 RequestNotifier = mentor_requests.RequestNotifier
 ModMessage = mod_message.ModMessage
+PinnedMessage = pinned_message.PinnedMessage
 StreamingEvents = streaming_events.StreamingEvents
 TrackReact = track_react.TrackReact

cogs/pinned_message.py

@@ -0,0 +1,66 @@
+"""Discord Cog to keep a message "pinned" at the end of a discussion."""
+
+import logging
+
+import discord
+from discord.ext import commands
+
+from cogs import base_cog
+
+logger = logging.getLogger(__name__)
+
+
+class PinnedMessage(base_cog.BaseCog):
+    """Keep a message pinned to the end of a channel."""
+
+    qualified_name = "Pinned Message"
+
+    def __init__(
+        self,
+        bot: commands.Bot,
+        messages: dict[int, str],
+        **kwargs,
+    ) -> None:
+        super().__init__(bot=bot, **kwargs)
+        self.bot = bot
+        self.messages: dict[int, str] = messages
+        self.last_message: dict[int, discord.Message] = {}
+
+    @commands.Cog.listener()
+    async def on_ready(self) -> None:
+        """Popular prior messages from channel histories."""
+        if self.bot.user:
+            for channel_id, content in self.messages.items():
+                message = await self.find_prior_message(channel_id, content)
+                if message:
+                    self.last_message[channel_id] = message
+
+    async def find_prior_message(self, channel_id: int, content: str) -> None | discord.Message:
+        """Return a prior message from a channel history."""
+        assert self.bot.user is not None
+        for guild in self.bot.guilds:
+            channel = guild.get_channel(channel_id)
+            if isinstance(channel, discord.TextChannel):
+                async for message in channel.history(limit=50, oldest_first=None):
+                    if message.author.id == self.bot.user.id and message.content == content:
+                        return message
+        return None
+
+    async def bump_message(self, channel: discord.TextChannel) -> None:
+        """Bump a pinned message in a channel."""
+        if last := self.last_message.get(channel.id):
+            await last.delete()
+
+        msg = await channel.send(self.messages[channel.id], silent=True)
+        self.last_message[channel.id] = msg
+
+    @commands.Cog.listener()
+    async def on_message(self, message: discord.Message) -> None:
+        """Move message to the end of the channel."""
+        if message.author.bot:
+            return
+        if not isinstance(message.channel, discord.TextChannel):
+            return
+        if message.channel.id not in self.messages:
+            return
+        await self.bump_message(message.channel)

conf.py

@@ -7,6 +7,7 @@
     "CloseSupportThread",
     "InclusiveLanguage",
     "ModMessage",
+    "PinnedMessage",
     "RequestNotifier",
     "StreamingEvents",
     "TrackReact",
@@ -129,3 +130,16 @@
 
 # CloseSupportThread
 SUPPORT_RESOLVED = "✅"
+
+
+# PinnedMessage
+PINNED_MESSAGES = {
+    # Test channel in test server.
+    1091223069407842306: "This is a pinned message.",
+    # Exercism photo channel
+    1203795616594010192: """\
+This is the photos channel. It is for sharing _your photographs_, not images.
+If you did not take the photo yourself with a camera, please do not post it!
+If it is not a photograph (an image captured by a camera), it will be deleted.
+When responding to messages, please remember to use a thread. Thank you!""",
+}

exercism_discord_bot.py

@@ -104,6 +104,7 @@ def get_cogs(self) -> dict[commands.CogMeta, dict[str, Any]]:
                 "pattern_response": conf.EXCLUSIVE_LANGUAGE
             },
             cogs.ModMessage: {"canned_messages": conf.CANNED_MESSAGES},
+            cogs.PinnedMessage: {"messages": conf.PINNED_MESSAGES},
             cogs.RequestNotifier: {
                 "channel_id": int(find_setting("MENTOR_REQUEST_CHANNEL")),
                 "sqlite_db": find_setting("SQLITE_DB"),