1 files changed, 49 insertions, 7 deletions
diff --git a/synapse/federation/transport/client.py b/synapse/federation/transport/client.py
index fe29bcfd4b..9fc4c31c93 100644
--- a/synapse/federation/transport/client.py
+++ b/synapse/federation/transport/client.py
@@ -21,6 +21,7 @@ from typing import (
     Callable,
     Collection,
     Dict,
+    Generator,
     Iterable,
     List,
     Mapping,
@@ -149,6 +150,42 @@ class TransportLayerClient:
         )
 
     @log_function
+    async def timestamp_to_event(
+        self, destination: str, room_id: str, timestamp: int, direction: str
+    ) -> Union[JsonDict, List]:
+        """
+        Calls a remote federating server at `destination` asking for their
+        closest event to the given timestamp in the given direction.
+
+        Args:
+            destination: Domain name of the remote homeserver
+            room_id: Room to fetch the event from
+            timestamp: The point in time (inclusive) we should navigate from in
+                the given direction to find the closest event.
+            direction: ["f"|"b"] to indicate whether we should navigate forward
+                or backward from the given timestamp to find the closest event.
+
+        Returns:
+            Response dict received from the remote homeserver.
+
+        Raises:
+            Various exceptions when the request fails
+        """
+        path = _create_path(
+            FEDERATION_UNSTABLE_PREFIX,
+            "/org.matrix.msc3030/timestamp_to_event/%s",
+            room_id,
+        )
+
+        args = {"ts": [str(timestamp)], "dir": [direction]}
+
+        remote_response = await self.client.get_json(
+            destination, path=path, args=args, try_trailing_slash_on_400=True
+        )
+
+        return remote_response
+
+    @log_function
     async def send_transaction(
         self,
         transaction: Transaction,
@@ -199,11 +236,16 @@ class TransportLayerClient:
 
     @log_function
     async def make_query(
-        self, destination, query_type, args, retry_on_dns_fail, ignore_backoff=False
-    ):
+        self,
+        destination: str,
+        query_type: str,
+        args: dict,
+        retry_on_dns_fail: bool,
+        ignore_backoff: bool = False,
+    ) -> JsonDict:
         path = _create_v1_path("/query/%s", query_type)
 
-        content = await self.client.get_json(
+        return await self.client.get_json(
             destination=destination,
             path=path,
             args=args,
@@ -212,8 +254,6 @@ class TransportLayerClient:
             ignore_backoff=ignore_backoff,
         )
 
-        return content
-
     @log_function
     async def make_membership_event(
         self,
@@ -1281,7 +1321,7 @@ class SendJoinResponse:
 
 
 @ijson.coroutine
-def _event_parser(event_dict: JsonDict):
+def _event_parser(event_dict: JsonDict) -> Generator[None, Tuple[str, Any], None]:
     """Helper function for use with `ijson.kvitems_coro` to parse key-value pairs
     to add them to a given dictionary.
     """
@@ -1292,7 +1332,9 @@ def _event_parser(event_dict: JsonDict):
 
 
 @ijson.coroutine
-def _event_list_parser(room_version: RoomVersion, events: List[EventBase]):
+def _event_list_parser(
+    room_version: RoomVersion, events: List[EventBase]
+) -> Generator[None, JsonDict, None]:
     """Helper function for use with `ijson.items_coro` to parse an array of
     events and add them to the given list.
     """