Infinite backfill with MSC2716 (#817)

Disabled by default, with non-infinite fallback mode as the default behavior

mautrix_telegram/example-config.yaml

@@ -337,34 +337,49 @@ bridge:
     create_group_on_invite: true
     # Settings for backfilling messages from Telegram.
     backfill:
-        # Whether or not the Telegram ghosts of logged in Matrix users should be
-        # invited to private chats when backfilling history from Telegram. This is
-        # usually needed to prevent rate limits and to allow timestamp massaging.
-        invite_own_puppet: true
-        # Maximum number of messages to backfill without using a takeout.
-        # The first time a takeout is used, the user has to manually approve it from a different
-        # device. If initial_limit or missed_limit are higher than this value, the bridge will ask
-        # the user to accept the takeout after logging in before syncing any chats.
-        takeout_limit: 100
-        # Maximum number of messages to backfill initially.
-        # Set to 0 to disable backfilling when creating portal, or -1 to disable the limit.
+        # Allow backfilling at all?
+        enable: true
+        # Use MSC2716 for backfilling?
         #
-        # N.B. Initial backfill will only start after member sync. Make sure your
-        #      max_initial_member_sync is set to a low enough value so it doesn't take forever.
-        initial_limit: 0
-        # Maximum number of messages to backfill if messages were missed while the bridge was
-        # disconnected. Note that this only works for logged in users and only if the chat isn't
-        # older than sync_update_limit
-        # Set to 0 to disable backfilling missed messages.
-        missed_limit: 50
-        # If using double puppeting, should notifications be disabled
-        # while the initial backfill is in progress?
-        disable_notifications: false
+        # This requires a server with MSC2716 support, which is currently an experimental feature in Synapse.
+        # It can be enabled by setting experimental_features -> msc2716_enabled to true in homeserver.yaml.
+        msc2716: false
+        # Use double puppets for backfilling?
+        #
+        # If using MSC2716, the double puppets must be in the appservice's user ID namespace
+        # (because the bridge can't use the double puppet access token with batch sending).
+        double_puppet_backfill: false
         # Whether or not to enable backfilling in normal groups.
         # Normal groups have numerous technical problems in Telegram, and backfilling normal groups
         # will likely cause problems if there are multiple Matrix users in the group.
         normal_groups: false
 
+        # Forward backfilling limits. These apply to both MSC2716 and legacy backfill.
+        forward:
+            # Number of messages to backfill immediately after creating a portal.
+            initial_limit: 10
+            # Number of messages to backfill when syncing chats.
+            sync_limit: 100
+
+        # Settings for incremental backfill of history. These only apply when using MSC2716.
+        incremental:
+            # Maximum number of messages to backfill per batch.
+            messages_per_batch: 100
+            # The number of seconds to wait after backfilling the batch of messages.
+            post_batch_delay: 20
+            # The maximum number of batches to backfill per portal, split by the chat type.
+            # If set to -1, all messages in the chat will eventually be backfilled.
+            max_batches:
+                # Direct chats
+                user: -1
+                # Normal groups. Note that the normal_groups option above must be enabled
+                # for these to be backfilled.
+                normal_group: -1
+                # Supergroups
+                supergroup: 10
+                # Broadcast channels
+                channel: -1
+
     # Overrides for base power levels.
     initial_power_level_overrides:
         user: {}