Add room context api

synapse/handlers/room.py

@@ -33,6 +33,7 @@ from collections import OrderedDict
 from unpaddedbase64 import decode_base64
 
 import logging
+import math
 import string
 
 logger = logging.getLogger(__name__)
@@ -747,6 +748,47 @@ class RoomListHandler(BaseHandler):
         defer.returnValue({"start": "START", "end": "END", "chunk": chunk})
 
 
+class RoomContextHandler(BaseHandler):
+    @defer.inlineCallbacks
+    def get_event_context(self, user, room_id, event_id, limit):
+        before_limit = math.floor(limit/2.)
+        after_limit = limit - before_limit
+
+        now_token = yield self.hs.get_event_sources().get_current_token()
+
+        results = yield self.store.get_events_around(
+            room_id, event_id, before_limit, after_limit
+        )
+
+        results["events_before"] = yield self._filter_events_for_client(
+            user.to_string(), results["events_before"]
+        )
+
+        results["events_after"] = yield self._filter_events_for_client(
+            user.to_string(), results["events_after"]
+        )
+
+        if results["events_after"]:
+            last_event_id = results["events_after"][-1].event_id
+        else:
+            last_event_id = event_id
+
+        state = yield self.store.get_state_for_events(
+            [last_event_id], None
+        )
+        results["state"] = state[last_event_id].values()
+
+        results["start"] = now_token.copy_and_replace(
+            "room_key", results["start"]
+        ).to_string()
+
+        results["end"] = now_token.copy_and_replace(
+            "room_key", results["end"]
+        ).to_string()
+
+        defer.returnValue(results)
+
+
 class RoomEventSource(object):
     def __init__(self, hs):
         self.store = hs.get_datastore()