From 12d40257520639a43cfaa3b6c03f45282615d09a Mon Sep 17 00:00:00 2001
From: Tulir Asokan <tulir@maunium.net>
Date: Tue, 20 Feb 2018 20:43:05 +0200
Subject: [PATCH] Implement Telegram->Matrix deletion bridging. Fixes #63

---
 ROADMAP.md                        |  2 +-
 example-config.yaml               |  3 ++
 mautrix_appservice/intent_api.py  | 10 ++++++
 mautrix_telegram/abstract_user.py | 51 ++++++++++++++++++++++++++++++-
 4 files changed, 64 insertions(+), 2 deletions(-)

diff --git a/ROADMAP.md b/ROADMAP.md
index 23b1f0e3..78b38cc4 100644
--- a/ROADMAP.md
+++ b/ROADMAP.md
@@ -46,7 +46,7 @@
   * [x] Audio messages
   * [x] Video messages
   * [x] Documents
-  * [ ] Message deletions (no way to tell difference between user-specific deletion and global deletion)
+  * [x] Message deletions
   * [ ] Message edits (not supported in Matrix)
   * [x] Avatars
   * [x] Presence
diff --git a/example-config.yaml b/example-config.yaml
index 221ff539..90166e14 100644
--- a/example-config.yaml
+++ b/example-config.yaml
@@ -69,6 +69,9 @@ bridge:
     edits_as_replies: False
     # Whether or not Matrix bot messages (type m.notice) should be bridged.
     bridge_notices: False
+    # The maximum number of simultaneous Telegram deletions to handle.
+    # A large number of simultaneous redactions could put strain on your homeserver.
+    max_telegram_delete: 10
 
     # The prefix for commands. Only required in non-management rooms.
     command_prefix: "!tg"
diff --git a/mautrix_appservice/intent_api.py b/mautrix_appservice/intent_api.py
index 94b894b0..f011f3c0 100644
--- a/mautrix_appservice/intent_api.py
+++ b/mautrix_appservice/intent_api.py
@@ -425,6 +425,16 @@ class IntentAPI:
 
         return self.send_state_event(room_id, "m.room.member", body, state_key=user_id)
 
+    def redact(self, room_id, event_id, reason=None, txn_id=None):
+        txn_id = txn_id or str(self.client.txn_id) + str(int(time() * 1000))
+        self.client.txn_id += 1
+        content = {}
+        if reason:
+            content["reason"] = reason
+        return self.client.request("PUT",
+                                   f"/rooms/{quote(room_id)}/redact/{quote(event_id)}/{txn_id}",
+                                   content)
+
     @staticmethod
     def _get_event_url(room_id, event_type, txn_id):
         if not room_id:
diff --git a/mautrix_telegram/abstract_user.py b/mautrix_telegram/abstract_user.py
index 260cc504..f93d1b92 100644
--- a/mautrix_telegram/abstract_user.py
+++ b/mautrix_telegram/abstract_user.py
@@ -18,12 +18,15 @@ import platform
 import os
 
 from telethon.tl.types import *
+from mautrix_appservice import MatrixRequestError
 
 from .tgclient import MautrixTelegramClient
 from .db import Message as DBMessage
 from . import portal as po, puppet as pu, __version__
 
 config = None
+# Value updated from config in init()
+MAX_DELETIONS = 10
 
 
 class AbstractUser:
@@ -106,6 +109,10 @@ class AbstractUser:
                       (UpdateShortChatMessage, UpdateShortMessage, UpdateNewChannelMessage,
                        UpdateNewMessage, UpdateEditMessage, UpdateEditChannelMessage)):
             await self.update_message(update)
+        elif isinstance(update, UpdateDeleteMessages):
+            await self.delete_message(update)
+        elif isinstance(update, UpdateDeleteChannelMessages):
+            await self.delete_channel_message(update)
         elif isinstance(update, (UpdateChatUserTyping, UpdateUserTyping)):
             await self.update_typing(update)
         elif isinstance(update, UpdateUserStatus):
@@ -206,6 +213,47 @@ class AbstractUser:
             return update, None, None
         return update, sender, portal
 
+    @staticmethod
+    async def _try_redact(portal, message):
+        if not portal:
+            return
+        try:
+            await portal.main_intent.redact(message.mx_room, message.mxid)
+        except MatrixRequestError:
+            pass
+
+    async def delete_message(self, update):
+        if len(update.messages) > MAX_DELETIONS:
+            return
+
+        for message in update.messages:
+            message = DBMessage.query.get((message, self.tgid))
+            if not message:
+                continue
+            self.db.delete(message)
+            number_left = DBMessage.query.filter(DBMessage.mxid == message.mxid,
+                                                 DBMessage.mx_room == message.mx_room).count()
+            if number_left == 0:
+                portal = po.Portal.get_by_mxid(message.mx_room)
+                await self._try_redact(portal, message)
+        self.db.commit()
+
+    async def delete_channel_message(self, update):
+        if len(update.messages) > MAX_DELETIONS:
+            return
+
+        portal = po.Portal.get_by_tgid(update.channel_id)
+        if not portal:
+            return
+
+        for message in update.messages:
+            message = DBMessage.query.get((message, portal.tgid))
+            if not message:
+                continue
+            self.db.delete(message)
+            await self._try_redact(portal, message)
+        self.db.commit()
+
     def update_message(self, original_update):
         update, sender, portal = self.get_message_details(original_update)
 
@@ -231,5 +279,6 @@ class AbstractUser:
 
 
 def init(context):
-    global config
+    global config, MAX_DELETIONS
     AbstractUser.az, AbstractUser.db, config, AbstractUser.loop, _ = context
+    MAX_DELETIONS = config.get("bridge.max_telegram_delete", 10)