Add a function to fetch the moved WebhookMessage from some Message.

Author: 00-kat

app/utils/__init__.py

@@ -21,6 +21,7 @@
     dynamic_timestamp,
     format_or_file,
     get_ghostty_guild,
+    get_moved_message,
     get_moved_message_author_id,
     get_or_create_webhook,
     message_can_be_moved,
@@ -44,6 +45,7 @@
     "escape_special",
     "format_or_file",
     "get_ghostty_guild",
+    "get_moved_message",
     "get_moved_message_author_id",
     "get_or_create_webhook",
     "is_dm",

app/utils/webhooks.py

@@ -395,6 +395,10 @@ def _sub_join(*strs: str) -> str:
 async def get_or_create_webhook(
     channel: discord.TextChannel | discord.ForumChannel, name: str = "Ghostty Moderator"
 ) -> discord.Webhook:
+    """
+    NOTE: if the intent of this webhook is for moving messages, do not change
+    the default value of `name`.
+    """
     webhooks = await channel.webhooks()
     for webhook in webhooks:
         if webhook.name == name:
@@ -510,6 +514,43 @@ def format_or_file(
     return full_message, None
 
 
+async def get_moved_message(message: discord.Message) -> discord.WebhookMessage | None:
+    """
+    Returns None if it could not be acquired, and discord.utils.MISSING if the
+    provided message is not a moved message.
+    """
+    if message.webhook_id is None or isinstance(
+        message.channel,
+        # These types can't even have a webhook.
+        discord.DMChannel | discord.GroupChannel | discord.PartialMessageable,
+    ):
+        return discord.utils.MISSING
+
+    if isinstance(message.channel, discord.Thread):
+        thread = message.channel
+        if (channel := message.channel.parent) is None:
+            return None
+    else:
+        channel = message.channel
+        thread = discord.utils.MISSING
+
+    for webhook in await channel.webhooks():
+        if webhook.id == message.webhook_id:
+            break
+    else:
+        return discord.utils.MISSING
+    if webhook.name != "Ghostty Moderator":
+        # More heuristics to determine if a webhook message is a moved message.
+        return discord.utils.MISSING
+
+    try:
+        return await webhook.fetch_message(message.id, thread=thread)
+    except discord.Forbidden:
+        return None
+    except discord.NotFound:
+        return discord.utils.MISSING
+
+
 def _find_snowflake(
     content: str, type_: str, *, substring_start: int = 0
 ) -> tuple[int | None, int | None]: