diff --git a/synapse/handlers/room_batch.py b/synapse/handlers/room_batch.py
new file mode 100644
index 0000000000..51dd4e7555
--- /dev/null
+++ b/synapse/handlers/room_batch.py
@@ -0,0 +1,423 @@
+import logging
+from typing import TYPE_CHECKING, List, Tuple
+
+from synapse.api.constants import EventContentFields, EventTypes
+from synapse.appservice import ApplicationService
+from synapse.http.servlet import assert_params_in_dict
+from synapse.types import JsonDict, Requester, UserID, create_requester
+from synapse.util.stringutils import random_string
+
+if TYPE_CHECKING:
+ from synapse.server import HomeServer
+
+logger = logging.getLogger(__name__)
+
+
+class RoomBatchHandler:
+ def __init__(self, hs: "HomeServer"):
+ self.hs = hs
+ self.store = hs.get_datastore()
+ self.state_store = hs.get_storage().state
+ self.event_creation_handler = hs.get_event_creation_handler()
+ self.room_member_handler = hs.get_room_member_handler()
+ self.auth = hs.get_auth()
+
+ async def inherit_depth_from_prev_ids(self, prev_event_ids: List[str]) -> int:
+ """Finds the depth which would sort it after the most-recent
+ prev_event_id but before the successors of those events. If no
+ successors are found, we assume it's an historical extremity part of the
+ current batch and use the same depth of the prev_event_ids.
+
+ Args:
+ prev_event_ids: List of prev event IDs
+
+ Returns:
+ Inherited depth
+ """
+ (
+ most_recent_prev_event_id,
+ most_recent_prev_event_depth,
+ ) = await self.store.get_max_depth_of(prev_event_ids)
+
+ # We want to insert the historical event after the `prev_event` but before the successor event
+ #
+ # We inherit depth from the successor event instead of the `prev_event`
+ # because events returned from `/messages` are first sorted by `topological_ordering`
+ # which is just the `depth` and then tie-break with `stream_ordering`.
+ #
+ # We mark these inserted historical events as "backfilled" which gives them a
+ # negative `stream_ordering`. If we use the same depth as the `prev_event`,
+ # then our historical event will tie-break and be sorted before the `prev_event`
+ # when it should come after.
+ #
+ # We want to use the successor event depth so they appear after `prev_event` because
+ # it has a larger `depth` but before the successor event because the `stream_ordering`
+ # is negative before the successor event.
+ successor_event_ids = await self.store.get_successor_events(
+ [most_recent_prev_event_id]
+ )
+
+ # If we can't find any successor events, then it's a forward extremity of
+ # historical messages and we can just inherit from the previous historical
+ # event which we can already assume has the correct depth where we want
+ # to insert into.
+ if not successor_event_ids:
+ depth = most_recent_prev_event_depth
+ else:
+ (
+ _,
+ oldest_successor_depth,
+ ) = await self.store.get_min_depth_of(successor_event_ids)
+
+ depth = oldest_successor_depth
+
+ return depth
+
+ def create_insertion_event_dict(
+ self, sender: str, room_id: str, origin_server_ts: int
+ ) -> JsonDict:
+ """Creates an event dict for an "insertion" event with the proper fields
+ and a random batch ID.
+
+ Args:
+ sender: The event author MXID
+ room_id: The room ID that the event belongs to
+ origin_server_ts: Timestamp when the event was sent
+
+ Returns:
+ The new event dictionary to insert.
+ """
+
+ next_batch_id = random_string(8)
+ insertion_event = {
+ "type": EventTypes.MSC2716_INSERTION,
+ "sender": sender,
+ "room_id": room_id,
+ "content": {
+ EventContentFields.MSC2716_NEXT_BATCH_ID: next_batch_id,
+ EventContentFields.MSC2716_HISTORICAL: True,
+ },
+ "origin_server_ts": origin_server_ts,
+ }
+
+ return insertion_event
+
+ async def create_requester_for_user_id_from_app_service(
+ self, user_id: str, app_service: ApplicationService
+ ) -> Requester:
+ """Creates a new requester for the given user_id
+ and validates that the app service is allowed to control
+ the given user.
+
+ Args:
+ user_id: The author MXID that the app service is controlling
+ app_service: The app service that controls the user
+
+ Returns:
+ Requester object
+ """
+
+ await self.auth.validate_appservice_can_control_user_id(app_service, user_id)
+
+ return create_requester(user_id, app_service=app_service)
+
+ async def get_most_recent_auth_event_ids_from_event_id_list(
+ self, event_ids: List[str]
+ ) -> List[str]:
+ """Find the most recent auth event ids (derived from state events) that
+ allowed that message to be sent. We will use this as a base
+ to auth our historical messages against.
+
+ Args:
+ event_ids: List of event ID's to look at
+
+ Returns:
+ List of event ID's
+ """
+
+ (
+ most_recent_prev_event_id,
+ _,
+ ) = await self.store.get_max_depth_of(event_ids)
+ # mapping from (type, state_key) -> state_event_id
+ prev_state_map = await self.state_store.get_state_ids_for_event(
+ most_recent_prev_event_id
+ )
+ # List of state event ID's
+ prev_state_ids = list(prev_state_map.values())
+ auth_event_ids = prev_state_ids
+
+ return auth_event_ids
+
+ async def persist_state_events_at_start(
+ self,
+ state_events_at_start: List[JsonDict],
+ room_id: str,
+ initial_auth_event_ids: List[str],
+ app_service_requester: Requester,
+ ) -> List[str]:
+ """Takes all `state_events_at_start` event dictionaries and creates/persists
+ them as floating state events which don't resolve into the current room state.
+ They are floating because they reference a fake prev_event which doesn't connect
+ to the normal DAG at all.
+
+ Args:
+ state_events_at_start:
+ room_id: Room where you want the events persisted in.
+ initial_auth_event_ids: These will be the auth_events for the first
+ state event created. Each event created afterwards will be
+ added to the list of auth events for the next state event
+ created.
+ app_service_requester: The requester of an application service.
+
+ Returns:
+ List of state event ID's we just persisted
+ """
+ assert app_service_requester.app_service
+
+ state_event_ids_at_start = []
+ auth_event_ids = initial_auth_event_ids.copy()
+ for state_event in state_events_at_start:
+ assert_params_in_dict(
+ state_event, ["type", "origin_server_ts", "content", "sender"]
+ )
+
+ logger.debug(
+ "RoomBatchSendEventRestServlet inserting state_event=%s, auth_event_ids=%s",
+ state_event,
+ auth_event_ids,
+ )
+
+ event_dict = {
+ "type": state_event["type"],
+ "origin_server_ts": state_event["origin_server_ts"],
+ "content": state_event["content"],
+ "room_id": room_id,
+ "sender": state_event["sender"],
+ "state_key": state_event["state_key"],
+ }
+
+ # Mark all events as historical
+ event_dict["content"][EventContentFields.MSC2716_HISTORICAL] = True
+
+ # Make the state events float off on their own so we don't have a
+ # bunch of `@mxid joined the room` noise between each batch
+ fake_prev_event_id = "$" + random_string(43)
+
+ # TODO: This is pretty much the same as some other code to handle inserting state in this file
+ if event_dict["type"] == EventTypes.Member:
+ membership = event_dict["content"].get("membership", None)
+ event_id, _ = await self.room_member_handler.update_membership(
+ await self.create_requester_for_user_id_from_app_service(
+ state_event["sender"], app_service_requester.app_service
+ ),
+ target=UserID.from_string(event_dict["state_key"]),
+ room_id=room_id,
+ action=membership,
+ content=event_dict["content"],
+ outlier=True,
+ prev_event_ids=[fake_prev_event_id],
+ # Make sure to use a copy of this list because we modify it
+ # later in the loop here. Otherwise it will be the same
+ # reference and also update in the event when we append later.
+ auth_event_ids=auth_event_ids.copy(),
+ )
+ else:
+ # TODO: Add some complement tests that adds state that is not member joins
+ # and will use this code path. Maybe we only want to support join state events
+ # and can get rid of this `else`?
+ (
+ event,
+ _,
+ ) = await self.event_creation_handler.create_and_send_nonmember_event(
+ await self.create_requester_for_user_id_from_app_service(
+ state_event["sender"], app_service_requester.app_service
+ ),
+ event_dict,
+ outlier=True,
+ prev_event_ids=[fake_prev_event_id],
+ # Make sure to use a copy of this list because we modify it
+ # later in the loop here. Otherwise it will be the same
+ # reference and also update in the event when we append later.
+ auth_event_ids=auth_event_ids.copy(),
+ )
+ event_id = event.event_id
+
+ state_event_ids_at_start.append(event_id)
+ auth_event_ids.append(event_id)
+
+ return state_event_ids_at_start
+
+ async def persist_historical_events(
+ self,
+ events_to_create: List[JsonDict],
+ room_id: str,
+ initial_prev_event_ids: List[str],
+ inherited_depth: int,
+ auth_event_ids: List[str],
+ app_service_requester: Requester,
+ ) -> List[str]:
+ """Create and persists all events provided sequentially. Handles the
+ complexity of creating events in chronological order so they can
+ reference each other by prev_event but still persists in
+ reverse-chronoloical order so they have the correct
+ (topological_ordering, stream_ordering) and sort correctly from
+ /messages.
+
+ Args:
+ events_to_create: List of historical events to create in JSON
+ dictionary format.
+ room_id: Room where you want the events persisted in.
+ initial_prev_event_ids: These will be the prev_events for the first
+ event created. Each event created afterwards will point to the
+ previous event created.
+ inherited_depth: The depth to create the events at (you will
+ probably by calling inherit_depth_from_prev_ids(...)).
+ auth_event_ids: Define which events allow you to create the given
+ event in the room.
+ app_service_requester: The requester of an application service.
+
+ Returns:
+ List of persisted event IDs
+ """
+ assert app_service_requester.app_service
+
+ prev_event_ids = initial_prev_event_ids.copy()
+
+ event_ids = []
+ events_to_persist = []
+ for ev in events_to_create:
+ assert_params_in_dict(ev, ["type", "origin_server_ts", "content", "sender"])
+
+ event_dict = {
+ "type": ev["type"],
+ "origin_server_ts": ev["origin_server_ts"],
+ "content": ev["content"],
+ "room_id": room_id,
+ "sender": ev["sender"], # requester.user.to_string(),
+ "prev_events": prev_event_ids.copy(),
+ }
+
+ # Mark all events as historical
+ event_dict["content"][EventContentFields.MSC2716_HISTORICAL] = True
+
+ event, context = await self.event_creation_handler.create_event(
+ await self.create_requester_for_user_id_from_app_service(
+ ev["sender"], app_service_requester.app_service
+ ),
+ event_dict,
+ prev_event_ids=event_dict.get("prev_events"),
+ auth_event_ids=auth_event_ids,
+ historical=True,
+ depth=inherited_depth,
+ )
+ logger.debug(
+ "RoomBatchSendEventRestServlet inserting event=%s, prev_event_ids=%s, auth_event_ids=%s",
+ event,
+ prev_event_ids,
+ auth_event_ids,
+ )
+
+ assert self.hs.is_mine_id(event.sender), "User must be our own: %s" % (
+ event.sender,
+ )
+
+ events_to_persist.append((event, context))
+ event_id = event.event_id
+
+ event_ids.append(event_id)
+ prev_event_ids = [event_id]
+
+ # Persist events in reverse-chronological order so they have the
+ # correct stream_ordering as they are backfilled (which decrements).
+ # Events are sorted by (topological_ordering, stream_ordering)
+ # where topological_ordering is just depth.
+ for (event, context) in reversed(events_to_persist):
+ await self.event_creation_handler.handle_new_client_event(
+ await self.create_requester_for_user_id_from_app_service(
+ event["sender"], app_service_requester.app_service
+ ),
+ event=event,
+ context=context,
+ )
+
+ return event_ids
+
+ async def handle_batch_of_events(
+ self,
+ events_to_create: List[JsonDict],
+ room_id: str,
+ batch_id_to_connect_to: str,
+ initial_prev_event_ids: List[str],
+ inherited_depth: int,
+ auth_event_ids: List[str],
+ app_service_requester: Requester,
+ ) -> Tuple[List[str], str]:
+ """
+ Handles creating and persisting all of the historical events as well
+ as insertion and batch meta events to make the batch navigable in the DAG.
+
+ Args:
+ events_to_create: List of historical events to create in JSON
+ dictionary format.
+ room_id: Room where you want the events created in.
+ batch_id_to_connect_to: The batch_id from the insertion event you
+ want this batch to connect to.
+ initial_prev_event_ids: These will be the prev_events for the first
+ event created. Each event created afterwards will point to the
+ previous event created.
+ inherited_depth: The depth to create the events at (you will
+ probably by calling inherit_depth_from_prev_ids(...)).
+ auth_event_ids: Define which events allow you to create the given
+ event in the room.
+ app_service_requester: The requester of an application service.
+
+ Returns:
+ Tuple containing a list of created events and the next_batch_id
+ """
+
+ # Connect this current batch to the insertion event from the previous batch
+ last_event_in_batch = events_to_create[-1]
+ batch_event = {
+ "type": EventTypes.MSC2716_BATCH,
+ "sender": app_service_requester.user.to_string(),
+ "room_id": room_id,
+ "content": {
+ EventContentFields.MSC2716_BATCH_ID: batch_id_to_connect_to,
+ EventContentFields.MSC2716_HISTORICAL: True,
+ },
+ # Since the batch event is put at the end of the batch,
+ # where the newest-in-time event is, copy the origin_server_ts from
+ # the last event we're inserting
+ "origin_server_ts": last_event_in_batch["origin_server_ts"],
+ }
+ # Add the batch event to the end of the batch (newest-in-time)
+ events_to_create.append(batch_event)
+
+ # Add an "insertion" event to the start of each batch (next to the oldest-in-time
+ # event in the batch) so the next batch can be connected to this one.
+ insertion_event = self.create_insertion_event_dict(
+ sender=app_service_requester.user.to_string(),
+ room_id=room_id,
+ # Since the insertion event is put at the start of the batch,
+ # where the oldest-in-time event is, copy the origin_server_ts from
+ # the first event we're inserting
+ origin_server_ts=events_to_create[0]["origin_server_ts"],
+ )
+ next_batch_id = insertion_event["content"][
+ EventContentFields.MSC2716_NEXT_BATCH_ID
+ ]
+ # Prepend the insertion event to the start of the batch (oldest-in-time)
+ events_to_create = [insertion_event] + events_to_create
+
+ # Create and persist all of the historical events
+ event_ids = await self.persist_historical_events(
+ events_to_create=events_to_create,
+ room_id=room_id,
+ initial_prev_event_ids=initial_prev_event_ids,
+ inherited_depth=inherited_depth,
+ auth_event_ids=auth_event_ids,
+ app_service_requester=app_service_requester,
+ )
+
+ return event_ids, next_batch_id
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