Send some ephemeral events to appservices (#8437)

Optionally sends typing, presence, and read receipt information to appservices.

synapse/handlers/receipts.py

@@ -13,9 +13,11 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 import logging
+from typing import List, Tuple
 
+from synapse.appservice import ApplicationService
 from synapse.handlers._base import BaseHandler
-from synapse.types import ReadReceipt, get_domain_from_id
+from synapse.types import JsonDict, ReadReceipt, get_domain_from_id
 from synapse.util.async_helpers import maybe_awaitable
 
 logger = logging.getLogger(__name__)
@@ -140,5 +142,36 @@ class ReceiptEventSource:
 
         return (events, to_key)
 
+    async def get_new_events_as(
+        self, from_key: int, service: ApplicationService
+    ) -> Tuple[List[JsonDict], int]:
+        """Returns a set of new receipt events that an appservice
+        may be interested in.
+
+        Args:
+            from_key: the stream position at which events should be fetched from
+            service: The appservice which may be interested
+        """
+        from_key = int(from_key)
+        to_key = self.get_current_key()
+
+        if from_key == to_key:
+            return [], to_key
+
+        # We first need to fetch all new receipts
+        rooms_to_events = await self.store.get_linearized_receipts_for_all_rooms(
+            from_key=from_key, to_key=to_key
+        )
+
+        # Then filter down to rooms that the AS can read
+        events = []
+        for room_id, event in rooms_to_events.items():
+            if not await service.matches_user_in_member_list(room_id, self.store):
+                continue
+
+            events.append(event)
+
+        return (events, to_key)
+
     def get_current_key(self, direction="f"):
         return self.store.get_max_receipt_stream_id()