Add config to manage how long logs are stored (modmail-dev#3257)

bot.py

@@ -653,6 +653,7 @@ async def on_ready(self):
 
         self.post_metadata.start()
         self.autoupdate.start()
+        self.log_expiry.start()
         self._started = True
 
     async def convert_emoji(self, name: str) -> str:
@@ -1772,6 +1773,18 @@ async def before_autoupdate(self):
             logger.warning("Autoupdates disabled.")
             self.autoupdate.cancel()
             return
+
+    @tasks.loop(hours=1, reconnect=False)
+    async def log_expiry(self):
+        log_expire_after = self.config.get("log_expiration")
+        if log_expire_after == isodate.Duration():
+            return self.log_expiry.stop()
+
+        now = discord.utils.utcnow()
+        expiration_datetime = now - log_expire_after
+        expired_logs = await self.db.logs.delete_many({"closed_at": {"$lte": str(expiration_datetime)}})
+
+        logger.info(f"Deleted {expired_logs.deleted_count} expired logs.")
 
     def format_channel_name(self, author, exclude_channel=None, force_null=False):
         """Sanitises a username for use with text channel names

core/config.py

@@ -36,6 +36,7 @@ class ConfigManager:
         "account_age": isodate.Duration(),
         "guild_age": isodate.Duration(),
         "thread_cooldown": isodate.Duration(),
+        "log_expiration": isodate.Duration(),
         "reply_without_command": False,
         "anon_reply_without_command": False,
         "plain_reply_without_command": False,
@@ -183,7 +184,7 @@ class ConfigManager:
 
     colors = {"mod_color", "recipient_color", "main_color", "error_color"}
 
-    time_deltas = {"account_age", "guild_age", "thread_auto_close", "thread_cooldown"}
+    time_deltas = {"account_age", "guild_age", "thread_auto_close", "thread_cooldown", "log_expiration"}
 
     booleans = {
         "use_user_id_channel_name",

core/config_help.json

@@ -373,6 +373,17 @@
             "To disable thread cooldown, do `{prefix}config del thread_cooldown`."
         ]
     },
+	"log_expiration": {
+		"default": "Never",
+		"description": "The duration closed threads will be stored within the database before deletion. Logs that have been closed for longer than this duration will be deleted automatically.",
+		"examples": [
+		  "`{prefix}config set log_expiration P12DT3H` (stands for 12 days and 3 hours in [ISO-8601 Duration Format](https://en.wikipedia.org/wiki/ISO_8601#Durations))",
+		  "`{prefix}config set log_expiration 3 days and 5 hours` (accepted readable time)"
+		],
+		"notes": [
+		  "To disable log expiration, do `{prefix}config del log_expiration`."
+		]
+	  },
     "thread_cancelled": {
         "default": "\"Cancelled\"",
         "description": "This is the message to display when a thread times out and creation is cancelled.",