Improve backfilling to fetch less redundant messages

mautrix_telegram/portal.py

@@ -2789,7 +2789,7 @@ class Portal(DBPortal, BasePortal):
         source: u.User,
         is_initial: bool = False,
         limit: int | None = None,
-        last_id: int | None = None,
+        last_tgid: int | None = None,
     ) -> None:
         limit = limit or (
             self.config["bridge.backfill.initial_limit"]
@@ -2800,43 +2800,39 @@ class Portal(DBPortal, BasePortal):
             return
         if not self.config["bridge.backfill.normal_groups"] and self.peer_type == "chat":
             return
-        last = await DBMessage.find_last(
+        last_in_room = await DBMessage.find_last(
             self.mxid, (source.tgid if self.peer_type != "channel" else self.tgid)
         )
-        min_id = last.tgid if last else 0
-        if last_id is None:
+        min_id = last_in_room.tgid if last_in_room else 0
+        if last_tgid is None:
             messages = await source.client.get_messages(self.peer, limit=1)
             if not messages:
                 # The chat seems empty
                 return
-            last_id = messages[0].id
-        if last_id <= min_id:
+            last_tgid = messages[0].id
+        if last_tgid <= min_id or (last_tgid == 1 and self.peer_type == "channel"):
             # Nothing to backfill
             return
         if limit < 0:
-            limit = last_id - min_id
+            limit = last_tgid - min_id
             self.log.debug(
-                f"Backfilling approximately {last_id - min_id} messages through {source.mxid}"
+                f"Backfilling approximately {last_tgid - min_id} messages through {source.mxid}"
             )
         elif self.peer_type == "channel":
-            # This is a channel or supergroup, so we'll backfill messages based on the ID.
-            # There are some cases, such as deleted messages, where this may backfill less
-            # messages than the limit.
-            min_id = max(last_id - limit, min_id)
+            min_id = max(last_tgid - limit, min_id)
             self.log.debug(
-                f"Backfilling messages after ID {min_id} (last message: {last_id}) "
+                f"Backfilling messages after ID {min_id} (last message: {last_tgid}) "
                 f"through {source.mxid}"
             )
         else:
-            # Private chats and normal groups don't have their own message ID namespace,
-            # which means we'll have to fetch messages a different way.
-            # The _backfill_messages method will detect min_id=None and not use reverse=True
-            min_id = None
+            # This limit will be higher than the actual message count if there are any messages
+            # in other DMs or normal groups, but that's not too bad.
+            limit = min(last_tgid - min_id, limit)
             self.log.debug(f"Backfilling up to {limit} messages through {source.mxid}")
         with self.backfill_lock:
             await self._backfill(source, min_id, limit)
 
-    async def _backfill(self, source: u.User, min_id: int | None, limit: int) -> None:
+    async def _backfill(self, source: u.User, min_id: int, limit: int) -> None:
         self.backfill_leave = set()
         if (
             self.peer_type == "user"
@@ -2854,38 +2850,55 @@ class Portal(DBPortal, BasePortal):
             if limit > self.config["bridge.backfill.takeout_limit"]:
                 self.log.debug(f"Opening takeout client for {source.tgid}")
                 async with client.takeout(**self._takeout_options) as takeout:
-                    count = await self._backfill_messages(source, min_id, limit, takeout)
+                    count, handled = await self._backfill_messages(source, min_id, limit, takeout)
             else:
-                count = await self._backfill_messages(source, min_id, limit, client)
+                count, handled = await self._backfill_messages(source, min_id, limit, client)
 
         for intent in self.backfill_leave:
             self.log.trace("Leaving room with %s post-backfill", intent.mxid)
             await intent.leave_room(self.mxid)
         self.backfill_leave = None
-        self.log.info("Backfilled %d messages through %s", count, source.mxid)
+        self.log.info(
+            "Backfilled %d (of %d fetched) messages through %s", handled, count, source.mxid
+        )
 
     async def _backfill_messages(
-        self, source: u.User, min_id: int | None, limit: int, client: MautrixTelegramClient
-    ) -> int:
-        count = 0
+        self, source: u.User, min_id: int, limit: int, client: MautrixTelegramClient
+    ) -> tuple[int, int]:
+        count = handled_count = 0
         entity = await self.get_input_entity(source)
-        if min_id is not None:
+        if self.peer_type == "channel":
+            # This is a channel or supergroup, so we'll backfill messages based on the ID.
+            # There are some cases, such as deleted messages, where this may backfill less
+            # messages than the limit.
             self.log.debug(f"Iterating all messages starting with {min_id} (approx: {limit})")
             messages = client.iter_messages(entity, reverse=True, min_id=min_id)
             async for message in messages:
-                await self._handle_telegram_backfill_message(source, message)
                 count += 1
+                was_handled = await self._handle_telegram_backfill_message(source, message)
+                handled_count += 1 if was_handled else 0
         else:
-            self.log.debug(f"Fetching up to {limit} most recent messages")
-            messages = await client.get_messages(entity, limit=limit)
+            # Private chats and normal groups don't have their own message ID namespace,
+            # which means we'll have to fetch messages a different way.
+            self.log.debug(
+                f"Fetching up to {limit} most recent messages, ignoring anything before {min_id}"
+            )
+            messages = await client.get_messages(entity, min_id=min_id, limit=limit)
             for message in reversed(messages):
-                await self._handle_telegram_backfill_message(source, message)
                 count += 1
-        return count
+                if message.id <= min_id:
+                    self.log.trace(
+                        f"Skipping {message.id} in backfill response as it's lower than "
+                        f"the last bridged message ({min_id})"
+                    )
+                    continue
+                was_handled = await self._handle_telegram_backfill_message(source, message)
+                handled_count += 1 if was_handled else 0
+        return count, handled_count
 
     async def _handle_telegram_backfill_message(
         self, source: au.AbstractUser, msg: Message | MessageService
-    ) -> None:
+    ) -> bool:
         if msg.from_id and isinstance(msg.from_id, (PeerUser, PeerChannel)):
             sender = await p.Puppet.get_by_peer(msg.from_id)
         elif isinstance(msg.peer_id, PeerUser):
@@ -2898,14 +2911,17 @@ class Portal(DBPortal, BasePortal):
         if isinstance(msg, MessageService):
             if isinstance(msg.action, MessageActionContactSignUp):
                 await self.handle_telegram_joined(source, sender, msg, backfill=True)
+                return True
             else:
                 self.log.debug(
                     f"Unhandled service message {type(msg.action).__name__} in backfill"
                 )
         elif isinstance(msg, Message):
             await self.handle_telegram_message(source, sender, msg)
+            return True
         else:
             self.log.debug(f"Unhandled message type {type(msg).__name__} in backfill")
+        return False
 
     def _split_dm_reaction_counts(self, counts: list[ReactionCount]) -> list[MessagePeerReaction]:
         if len(counts) == 1: