Add a Synapse Module for configuring presence update routing (#9491)

At the moment, if you'd like to share presence between local or remote users, those users must be sharing a room together. This isn't always the most convenient or useful situation though.

This PR adds a module to Synapse that will allow deployments to set up extra logic on where presence updates should be routed. The module must implement two methods, `get_users_for_states` and `get_interested_users`. These methods are given presence updates or user IDs and must return information that Synapse will use to grant passing presence updates around.

A method is additionally added to `ModuleApi` which allows triggering a set of users to receive the current, online presence information for all users they are considered interested in. This is the equivalent of that user receiving presence information during an initial sync. 

The goal of this module is to be fairly generic and useful for a variety of applications, with hard requirements being:

* Sending state for a specific set or all known users to a defined set of local and remote users.
* The ability to trigger an initial sync for specific users, so they receive all current state.

1 files changed, 172 insertions, 3 deletions

diff --git a/tests/module_api/test_api.py b/tests/module_api/test_api.py
index edacd1b566..1d1fceeecf 100644
--- a/tests/module_api/test_api.py
+++ b/tests/module_api/test_api.py
@@ -14,25 +14,37 @@
 # limitations under the License.
 from mock import Mock
 
+from synapse.api.constants import EduTypes
 from synapse.events import EventBase
+from synapse.federation.units import Transaction
+from synapse.handlers.presence import UserPresenceState
 from synapse.rest import admin
-from synapse.rest.client.v1 import login, room
+from synapse.rest.client.v1 import login, presence, room
 from synapse.types import create_requester
 
-from tests.unittest import HomeserverTestCase
+from tests.events.test_presence_router import send_presence_update, sync_presence
+from tests.test_utils.event_injection import inject_member_event
+from tests.unittest import FederatingHomeserverTestCase, override_config
 
 
-class ModuleApiTestCase(HomeserverTestCase):
+class ModuleApiTestCase(FederatingHomeserverTestCase):
     servlets = [
         admin.register_servlets,
         login.register_servlets,
         room.register_servlets,
+        presence.register_servlets,
     ]
 
     def prepare(self, reactor, clock, homeserver):
         self.store = homeserver.get_datastore()
         self.module_api = homeserver.get_module_api()
         self.event_creation_handler = homeserver.get_event_creation_handler()
+        self.sync_handler = homeserver.get_sync_handler()
+
+    def make_homeserver(self, reactor, clock):
+        return self.setup_test_homeserver(
+            federation_transport_client=Mock(spec=["send_transaction"]),
+        )
 
     def test_can_register_user(self):
         """Tests that an external module can register a user"""
@@ -205,3 +217,160 @@ class ModuleApiTestCase(HomeserverTestCase):
             )
         )
         self.assertFalse(is_in_public_rooms)
+
+    # The ability to send federation is required by send_local_online_presence_to.
+    @override_config({"send_federation": True})
+    def test_send_local_online_presence_to(self):
+        """Tests that send_local_presence_to_users sends local online presence to local users."""
+        # Create a user who will send presence updates
+        self.presence_receiver_id = self.register_user("presence_receiver", "monkey")
+        self.presence_receiver_tok = self.login("presence_receiver", "monkey")
+
+        # And another user that will send presence updates out
+        self.presence_sender_id = self.register_user("presence_sender", "monkey")
+        self.presence_sender_tok = self.login("presence_sender", "monkey")
+
+        # Put them in a room together so they will receive each other's presence updates
+        room_id = self.helper.create_room_as(
+            self.presence_receiver_id,
+            tok=self.presence_receiver_tok,
+        )
+        self.helper.join(room_id, self.presence_sender_id, tok=self.presence_sender_tok)
+
+        # Presence sender comes online
+        send_presence_update(
+            self,
+            self.presence_sender_id,
+            self.presence_sender_tok,
+            "online",
+            "I'm online!",
+        )
+
+        # Presence receiver should have received it
+        presence_updates, sync_token = sync_presence(self, self.presence_receiver_id)
+        self.assertEqual(len(presence_updates), 1)
+
+        presence_update = presence_updates[0]  # type: UserPresenceState
+        self.assertEqual(presence_update.user_id, self.presence_sender_id)
+        self.assertEqual(presence_update.state, "online")
+
+        # Syncing again should result in no presence updates
+        presence_updates, sync_token = sync_presence(
+            self, self.presence_receiver_id, sync_token
+        )
+        self.assertEqual(len(presence_updates), 0)
+
+        # Trigger sending local online presence
+        self.get_success(
+            self.module_api.send_local_online_presence_to(
+                [
+                    self.presence_receiver_id,
+                ]
+            )
+        )
+
+        # Presence receiver should have received online presence again
+        presence_updates, sync_token = sync_presence(
+            self, self.presence_receiver_id, sync_token
+        )
+        self.assertEqual(len(presence_updates), 1)
+
+        presence_update = presence_updates[0]  # type: UserPresenceState
+        self.assertEqual(presence_update.user_id, self.presence_sender_id)
+        self.assertEqual(presence_update.state, "online")
+
+        # Presence sender goes offline
+        send_presence_update(
+            self,
+            self.presence_sender_id,
+            self.presence_sender_tok,
+            "offline",
+            "I slink back into the darkness.",
+        )
+
+        # Trigger sending local online presence
+        self.get_success(
+            self.module_api.send_local_online_presence_to(
+                [
+                    self.presence_receiver_id,
+                ]
+            )
+        )
+
+        # Presence receiver should *not* have received offline state
+        presence_updates, sync_token = sync_presence(
+            self, self.presence_receiver_id, sync_token
+        )
+        self.assertEqual(len(presence_updates), 0)
+
+    @override_config({"send_federation": True})
+    def test_send_local_online_presence_to_federation(self):
+        """Tests that send_local_presence_to_users sends local online presence to remote users."""
+        # Create a user who will send presence updates
+        self.presence_sender_id = self.register_user("presence_sender", "monkey")
+        self.presence_sender_tok = self.login("presence_sender", "monkey")
+
+        # And a room they're a part of
+        room_id = self.helper.create_room_as(
+            self.presence_sender_id,
+            tok=self.presence_sender_tok,
+        )
+
+        # Mark them as online
+        send_presence_update(
+            self,
+            self.presence_sender_id,
+            self.presence_sender_tok,
+            "online",
+            "I'm online!",
+        )
+
+        # Make up a remote user to send presence to
+        remote_user_id = "@far_away_person:island"
+
+        # Create a join membership event for the remote user into the room.
+        # This allows presence information to flow from one user to the other.
+        self.get_success(
+            inject_member_event(
+                self.hs,
+                room_id,
+                sender=remote_user_id,
+                target=remote_user_id,
+                membership="join",
+            )
+        )
+
+        # The remote user would have received the existing room members' presence
+        # when they joined the room.
+        #
+        # Thus we reset the mock, and try sending online local user
+        # presence again
+        self.hs.get_federation_transport_client().send_transaction.reset_mock()
+
+        # Broadcast local user online presence
+        self.get_success(
+            self.module_api.send_local_online_presence_to([remote_user_id])
+        )
+
+        # Check that a presence update was sent as part of a federation transaction
+        found_update = False
+        calls = (
+            self.hs.get_federation_transport_client().send_transaction.call_args_list
+        )
+        for call in calls:
+            federation_transaction = call.args[0]  # type: Transaction
+
+            # Get the sent EDUs in this transaction
+            edus = federation_transaction.get_dict()["edus"]
+
+            for edu in edus:
+                # Make sure we're only checking presence-type EDUs
+                if edu["edu_type"] != EduTypes.Presence:
+                    continue
+
+                # EDUs can contain multiple presence updates
+                for presence_update in edu["content"]["push"]:
+                    if presence_update["user_id"] == self.presence_sender_id:
+                        found_update = True
+
+        self.assertTrue(found_update)