From ad4eab9862348fff16d66954930c0f8c3feae6e1 Mon Sep 17 00:00:00 2001
From: Brendan Abolivier <babolivier@matrix.org>
Date: Fri, 29 Oct 2021 18:28:29 +0200
Subject: [PATCH] Add a module API method to retrieve state from a room
 (#11204)

---
 changelog.d/11204.feature      |  1 +
 synapse/module_api/__init__.py | 49 ++++++++++++++++++++++++++++++++++
 tests/module_api/test_api.py   | 25 ++++++++++++++++-
 3 files changed, 74 insertions(+), 1 deletion(-)
 create mode 100644 changelog.d/11204.feature

diff --git a/changelog.d/11204.feature b/changelog.d/11204.feature
new file mode 100644
index 000000000..f58ed4b3d
--- /dev/null
+++ b/changelog.d/11204.feature
@@ -0,0 +1 @@
+Add a module API method to retrieve the current state of a room.
diff --git a/synapse/module_api/__init__.py b/synapse/module_api/__init__.py
index 36042ed2e..6e7f5238f 100644
--- a/synapse/module_api/__init__.py
+++ b/synapse/module_api/__init__.py
@@ -55,6 +55,7 @@ from synapse.types import (
     DomainSpecificString,
     JsonDict,
     Requester,
+    StateMap,
     UserID,
     UserInfo,
     create_requester,
@@ -89,6 +90,8 @@ __all__ = [
     "PRESENCE_ALL_USERS",
     "LoginResponse",
     "JsonDict",
+    "EventBase",
+    "StateMap",
 ]
 
 logger = logging.getLogger(__name__)
@@ -964,6 +967,52 @@ class ModuleApi:
         else:
             return []
 
+    async def get_room_state(
+        self,
+        room_id: str,
+        event_filter: Optional[Iterable[Tuple[str, Optional[str]]]] = None,
+    ) -> StateMap[EventBase]:
+        """Returns the current state of the given room.
+
+        The events are returned as a mapping, in which the key for each event is a tuple
+        which first element is the event's type and the second one is its state key.
+
+        Added in Synapse v1.47.0
+
+        Args:
+            room_id: The ID of the room to get state from.
+            event_filter: A filter to apply when retrieving events. None if no filter
+                should be applied. If provided, must be an iterable of tuples. A tuple's
+                first element is the event type and the second is the state key, or is
+                None if the state key should not be filtered on.
+                An example of a filter is:
+                    [
+                        ("m.room.member", "@alice:example.com"),  # Member event for @alice:example.com
+                        ("org.matrix.some_event", ""),  # State event of type "org.matrix.some_event"
+                                                        # with an empty string as its state key
+                        ("org.matrix.some_other_event", None),  # State events of type "org.matrix.some_other_event"
+                                                                # regardless of their state key
+                    ]
+        """
+        if event_filter:
+            # If a filter was provided, turn it into a StateFilter and retrieve a filtered
+            # view of the state.
+            state_filter = StateFilter.from_types(event_filter)
+            state_ids = await self._store.get_filtered_current_state_ids(
+                room_id,
+                state_filter,
+            )
+        else:
+            # If no filter was provided, get the whole state. We could also reuse the call
+            # to get_filtered_current_state_ids above, with `state_filter = StateFilter.all()`,
+            # but get_filtered_current_state_ids isn't cached and `get_current_state_ids`
+            # is, so using the latter when we can is better for perf.
+            state_ids = await self._store.get_current_state_ids(room_id)
+
+        state_events = await self._store.get_events(state_ids.values())
+
+        return {key: state_events[event_id] for key, event_id in state_ids.items()}
+
 
 class PublicRoomListManager:
     """Contains methods for adding to, removing from and querying whether a room
diff --git a/tests/module_api/test_api.py b/tests/module_api/test_api.py
index 37852852a..525b83141 100644
--- a/tests/module_api/test_api.py
+++ b/tests/module_api/test_api.py
@@ -15,7 +15,7 @@ from unittest.mock import Mock
 
 from twisted.internet import defer
 
-from synapse.api.constants import EduTypes
+from synapse.api.constants import EduTypes, EventTypes
 from synapse.events import EventBase
 from synapse.federation.units import Transaction
 from synapse.handlers.presence import UserPresenceState
@@ -509,6 +509,29 @@ class ModuleApiTestCase(HomeserverTestCase):
         self.assertEqual(res["displayname"], "simone")
         self.assertIsNone(res["avatar_url"])
 
+    def test_get_room_state(self):
+        """Tests that a module can retrieve the state of a room through the module API."""
+        user_id = self.register_user("peter", "hackme")
+        tok = self.login("peter", "hackme")
+
+        # Create a room and send some custom state in it.
+        room_id = self.helper.create_room_as(tok=tok)
+        self.helper.send_state(room_id, "org.matrix.test", {}, tok=tok)
+
+        # Check that the module API can successfully fetch state for the room.
+        state = self.get_success(
+            defer.ensureDeferred(self.module_api.get_room_state(room_id))
+        )
+
+        # Check that a few standard events are in the returned state.
+        self.assertIn((EventTypes.Create, ""), state)
+        self.assertIn((EventTypes.Member, user_id), state)
+
+        # Check that our custom state event is in the returned state.
+        self.assertEqual(state[("org.matrix.test", "")].sender, user_id)
+        self.assertEqual(state[("org.matrix.test", "")].state_key, "")
+        self.assertEqual(state[("org.matrix.test", "")].content, {})
+
 
 class ModuleApiWorkerTestCase(BaseMultiWorkerStreamTestCase):
     """For testing ModuleApi functionality in a multi-worker setup"""