From b582e59eee092ef463fc2e53c7e056f4e885fe2f Mon Sep 17 00:00:00 2001
From: Tulir Asokan <tulir@maunium.net>
Date: Wed, 12 Oct 2022 11:24:51 +0300
Subject: [PATCH] Add option to mark old chats as read even if they're unread
 on Telegram

---
 mautrix_telegram/config.py           |  1 +
 mautrix_telegram/example-config.yaml |  4 ++++
 mautrix_telegram/user.py             | 16 ++++++++++++++--
 3 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/mautrix_telegram/config.py b/mautrix_telegram/config.py
index 0d66c646..03edd641 100644
--- a/mautrix_telegram/config.py
+++ b/mautrix_telegram/config.py
@@ -162,6 +162,7 @@ class Config(BaseBridgeConfig):
         copy("bridge.backfill.msc2716")
         copy("bridge.backfill.double_puppet_backfill")
         copy("bridge.backfill.normal_groups")
+        copy("bridge.backfill.unread_hours_threshold")
         copy("bridge.backfill.forward.initial_limit")
         copy("bridge.backfill.forward.sync_limit")
         copy("bridge.backfill.incremental.messages_per_batch")
diff --git a/mautrix_telegram/example-config.yaml b/mautrix_telegram/example-config.yaml
index 3daf9dd0..ba9c5723 100644
--- a/mautrix_telegram/example-config.yaml
+++ b/mautrix_telegram/example-config.yaml
@@ -354,6 +354,10 @@ bridge:
         # will likely cause problems if there are multiple Matrix users in the group.
         normal_groups: false
 
+        # If a backfilled chat is older than this number of hours, mark it as read even if it's unread on Telegram.
+        # Set to -1 to let any chat be unread.
+        unread_hours_threshold: 720
+
         # Forward backfilling limits. These apply to both MSC2716 and legacy backfill.
         #
         # Using a negative initial limit is not recommended, as it would try to backfill everything in a single batch.
diff --git a/mautrix_telegram/user.py b/mautrix_telegram/user.py
index 3638602d..62ed8f28 100644
--- a/mautrix_telegram/user.py
+++ b/mautrix_telegram/user.py
@@ -16,7 +16,7 @@
 from __future__ import annotations
 
 from typing import TYPE_CHECKING, Any, AsyncGenerator, AsyncIterable, Awaitable, NamedTuple, cast
-from datetime import datetime, timezone
+from datetime import datetime, timedelta, timezone
 import asyncio
 import time
 
@@ -695,10 +695,22 @@ class User(DBUser, AbstractUser, BaseUser):
                 self.log.exception(f"Error while creating {portal.tgid_log}")
         if portal.mxid and puppet and puppet.is_real_user:
             tg_space = portal.tgid if portal.peer_type == "channel" else self.tgid
-            if dialog.unread_count == 0:
+            last_message_date: datetime = cast(datetime, dialog.date)
+            unread_threshold_hours = self.config["bridge.backfill.unread_hours_threshold"]
+            force_read = (
+                was_created
+                and unread_threshold_hours >= 0
+                and last_message_date + timedelta(hours=unread_threshold_hours) < datetime.now()
+            )
+            if dialog.unread_count == 0 or force_read:
                 # This is usually more reliable than finding a specific message
                 # e.g. if the last read message is a service message that isn't in the message db
                 last_read = await DBMessage.find_last(portal.mxid, tg_space)
+                if force_read:
+                    self.log.debug(
+                        f"Marking {portal.tgid_log} as read because the last message is from "
+                        f"{last_message_date} (unread threshold is {unread_threshold_hours} hours)"
+                    )
             else:
                 last_read = await DBMessage.get_one_by_tgid(
                     portal.tgid, tg_space, dialog.dialog.read_inbox_max_id