Add a relations handler to avoid duplication. (#12227)

Adds a handler layer between the REST and datastore layers for relations.

synapse/rest/client/relations.py

@@ -51,9 +51,7 @@ class RelationPaginationServlet(RestServlet):
         super().__init__()
         self.auth = hs.get_auth()
         self.store = hs.get_datastores().main
-        self.clock = hs.get_clock()
-        self._event_serializer = hs.get_event_client_serializer()
-        self.event_handler = hs.get_event_handler()
+        self._relations_handler = hs.get_relations_handler()
 
     async def on_GET(
         self,
@@ -65,16 +63,6 @@ class RelationPaginationServlet(RestServlet):
     ) -> Tuple[int, JsonDict]:
         requester = await self.auth.get_user_by_req(request, allow_guest=True)
 
-        await self.auth.check_user_in_room_or_world_readable(
-            room_id, requester.user.to_string(), allow_departed_users=True
-        )
-
-        # This gets the original event and checks that a) the event exists and
-        # b) the user is allowed to view it.
-        event = await self.event_handler.get_event(requester.user, room_id, parent_id)
-        if event is None:
-            raise SynapseError(404, "Unknown parent event.")
-
         limit = parse_integer(request, "limit", default=5)
         direction = parse_string(
             request, "org.matrix.msc3715.dir", default="b", allowed_values=["f", "b"]
@@ -90,9 +78,9 @@ class RelationPaginationServlet(RestServlet):
         if to_token_str:
             to_token = await StreamToken.from_string(self.store, to_token_str)
 
-        pagination_chunk = await self.store.get_relations_for_event(
+        result = await self._relations_handler.get_relations(
+            requester=requester,
             event_id=parent_id,
-            event=event,
             room_id=room_id,
             relation_type=relation_type,
             event_type=event_type,
@@ -102,30 +90,7 @@ class RelationPaginationServlet(RestServlet):
             to_token=to_token,
         )
 
-        events = await self.store.get_events_as_list(
-            [c["event_id"] for c in pagination_chunk.chunk]
-        )
-
-        now = self.clock.time_msec()
-        # Do not bundle aggregations when retrieving the original event because
-        # we want the content before relations are applied to it.
-        original_event = self._event_serializer.serialize_event(
-            event, now, bundle_aggregations=None
-        )
-        # The relations returned for the requested event do include their
-        # bundled aggregations.
-        aggregations = await self.store.get_bundled_aggregations(
-            events, requester.user.to_string()
-        )
-        serialized_events = self._event_serializer.serialize_events(
-            events, now, bundle_aggregations=aggregations
-        )
-
-        return_value = await pagination_chunk.to_dict(self.store)
-        return_value["chunk"] = serialized_events
-        return_value["original_event"] = original_event
-
-        return 200, return_value
+        return 200, result
 
 
 class RelationAggregationPaginationServlet(RestServlet):
@@ -245,9 +210,7 @@ class RelationAggregationGroupPaginationServlet(RestServlet):
         super().__init__()
         self.auth = hs.get_auth()
         self.store = hs.get_datastores().main
-        self.clock = hs.get_clock()
-        self._event_serializer = hs.get_event_client_serializer()
-        self.event_handler = hs.get_event_handler()
+        self._relations_handler = hs.get_relations_handler()
 
     async def on_GET(
         self,
@@ -260,18 +223,6 @@ class RelationAggregationGroupPaginationServlet(RestServlet):
     ) -> Tuple[int, JsonDict]:
         requester = await self.auth.get_user_by_req(request, allow_guest=True)
 
-        await self.auth.check_user_in_room_or_world_readable(
-            room_id,
-            requester.user.to_string(),
-            allow_departed_users=True,
-        )
-
-        # This checks that a) the event exists and b) the user is allowed to
-        # view it.
-        event = await self.event_handler.get_event(requester.user, room_id, parent_id)
-        if event is None:
-            raise SynapseError(404, "Unknown parent event.")
-
         if relation_type != RelationTypes.ANNOTATION:
             raise SynapseError(400, "Relation type must be 'annotation'")
 
@@ -286,9 +237,9 @@ class RelationAggregationGroupPaginationServlet(RestServlet):
         if to_token_str:
             to_token = await StreamToken.from_string(self.store, to_token_str)
 
-        result = await self.store.get_relations_for_event(
+        result = await self._relations_handler.get_relations(
+            requester=requester,
             event_id=parent_id,
-            event=event,
             room_id=room_id,
             relation_type=relation_type,
             event_type=event_type,
@@ -298,17 +249,7 @@ class RelationAggregationGroupPaginationServlet(RestServlet):
             to_token=to_token,
         )
 
-        events = await self.store.get_events_as_list(
-            [c["event_id"] for c in result.chunk]
-        )
-
-        now = self.clock.time_msec()
-        serialized_events = self._event_serializer.serialize_events(events, now)
-
-        return_value = await result.to_dict(self.store)
-        return_value["chunk"] = serialized_events
-
-        return 200, return_value
+        return 200, result
 
 
 def register_servlets(hs: "HomeServer", http_server: HttpServer) -> None: