Add room context api

synapse/handlers/__init__.py

@@ -17,7 +17,7 @@
 from synapse.appservice.api import ApplicationServiceApi
 from .register import RegistrationHandler
 from .room import (
-    RoomCreationHandler, RoomMemberHandler, RoomListHandler
+    RoomCreationHandler, RoomMemberHandler, RoomListHandler, RoomContextHandler,
 )
 from .message import MessageHandler
 from .events import EventStreamHandler, EventHandler
@@ -70,3 +70,4 @@ def __init__(self, hs):
         self.auth_handler = AuthHandler(hs)
         self.identity_handler = IdentityHandler(hs)
         self.search_handler = SearchHandler(hs)
+        self.room_context_handler = RoomContextHandler(hs)

synapse/handlers/room.py

@@ -33,6 +33,7 @@
 from unpaddedbase64 import decode_base64
 
 import logging
+import math
 import string
 
 logger = logging.getLogger(__name__)
@@ -747,6 +748,60 @@ def get_public_room_list(self):
         defer.returnValue({"start": "START", "end": "END", "chunk": chunk})
 
 
+class RoomContextHandler(BaseHandler):
+    @defer.inlineCallbacks
+    def get_event_context(self, user, room_id, event_id, limit):
+        """Retrieves events, pagination tokens and state around a given event
+        in a room.
+
+        Args:
+            user (UserID)
+            room_id (str)
+            event_id (str)
+            limit (int): The maximum number of events to return in total
+                (excluding state).
+
+        Returns:
+            dict
+        """
+        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()

synapse/rest/client/v1/room.py

@@ -397,6 +397,41 @@ def on_GET(self, request, room_id):
         defer.returnValue((200, res))
 
 
+class RoomEventContext(ClientV1RestServlet):
+    PATTERN = client_path_pattern(
+        "/rooms/(?P<room_id>[^/]*)/context/(?P<event_id>[^/]*)$"
+    )
+
+    def __init__(self, hs):
+        super(RoomEventContext, self).__init__(hs)
+        self.clock = hs.get_clock()
+
+    @defer.inlineCallbacks
+    def on_GET(self, request, room_id, event_id):
+        user, _ = yield self.auth.get_user_by_req(request)
+
+        limit = int(request.args.get("limit", [10])[0])
+
+        results = yield self.handlers.room_context_handler.get_event_context(
+            user, room_id, event_id, limit,
+        )
+
+        time_now = self.clock.time_msec()
+        results["events_before"] = [
+            serialize_event(event, time_now) for event in results["events_before"]
+        ]
+        results["events_after"] = [
+            serialize_event(event, time_now) for event in results["events_after"]
+        ]
+        results["state"] = [
+            serialize_event(event, time_now) for event in results["state"]
+        ]
+
+        logger.info("Responding with %r", results)
+
+        defer.returnValue((200, results))
+
+
 # TODO: Needs unit testing
 class RoomMembershipRestServlet(ClientV1RestServlet):
 
@@ -628,3 +663,4 @@ def register_servlets(hs, http_server):
     RoomRedactEventRestServlet(hs).register(http_server)
     RoomTypingRestServlet(hs).register(http_server)
     SearchRestServlet(hs).register(http_server)
+    RoomEventContext(hs).register(http_server)

synapse/storage/stream.py

@@ -23,7 +23,7 @@
 
 This is implemented by keeping two ordering columns: stream_ordering and
 topological_ordering. Stream ordering is basically insertion/received order
-(except for events from backfill requests). The topolgical_ordering is a
+(except for events from backfill requests). The topological_ordering is a
 weak ordering of events based on the pdu graph.
 
 This means that we have to have two different types of tokens, depending on
@@ -436,3 +436,138 @@ def _set_before_and_after(events, rows):
             internal = event.internal_metadata
             internal.before = str(RoomStreamToken(topo, stream - 1))
             internal.after = str(RoomStreamToken(topo, stream))
+
+    @defer.inlineCallbacks
+    def get_events_around(self, room_id, event_id, before_limit, after_limit):
+        """Retrieve events and pagination tokens around a given event in a
+        room.
+
+        Args:
+            room_id (str)
+            event_id (str)
+            before_limit (int)
+            after_limit (int)
+
+        Returns:
+            dict
+        """
+
+        results = yield self.runInteraction(
+            "get_events_around", self._get_events_around_txn,
+            room_id, event_id, before_limit, after_limit
+        )
+
+        events_before = yield self._get_events(
+            [e for e in results["before"]["event_ids"]],
+            get_prev_content=True
+        )
+
+        events_after = yield self._get_events(
+            [e for e in results["after"]["event_ids"]],
+            get_prev_content=True
+        )
+
+        defer.returnValue({
+            "events_before": events_before,
+            "events_after": events_after,
+            "start": results["before"]["token"],
+            "end": results["after"]["token"],
+        })
+
+    def _get_events_around_txn(self, txn, room_id, event_id, before_limit, after_limit):
+        """Retrieves event_ids and pagination tokens around a given event in a
+        room.
+
+        Args:
+            room_id (str)
+            event_id (str)
+            before_limit (int)
+            after_limit (int)
+
+        Returns:
+            dict
+        """
+
+        results = self._simple_select_one_txn(
+            txn,
+            "events",
+            keyvalues={
+                "event_id": event_id,
+                "room_id": room_id,
+            },
+            retcols=["stream_ordering", "topological_ordering"],
+        )
+
+        stream_ordering = results["stream_ordering"]
+        topological_ordering = results["topological_ordering"]
+
+        query_before = (
+            "SELECT topological_ordering, stream_ordering, event_id FROM events"
+            " WHERE room_id = ? AND (topological_ordering < ?"
+            " OR (topological_ordering = ? AND stream_ordering < ?))"
+            " ORDER BY topological_ordering DESC, stream_ordering DESC"
+            " LIMIT ?"
+        )
+
+        query_after = (
+            "SELECT topological_ordering, stream_ordering, event_id FROM events"
+            " WHERE room_id = ? AND (topological_ordering > ?"
+            " OR (topological_ordering = ? AND stream_ordering > ?))"
+            " ORDER BY topological_ordering ASC, stream_ordering ASC"
+            " LIMIT ?"
+        )
+
+        txn.execute(
+            query_before,
+            (
+                room_id, topological_ordering, topological_ordering,
+                stream_ordering, before_limit,
+            )
+        )
+
+        rows = self.cursor_to_dict(txn)
+        events_before = [r["event_id"] for r in rows]
+
+        if rows:
+            start_token = str(RoomStreamToken(
+                rows[0]["topological_ordering"],
+                rows[0]["stream_ordering"] - 1,
+            ))
+        else:
+            start_token = str(RoomStreamToken(
+                topological_ordering,
+                stream_ordering - 1,
+            ))
+
+        txn.execute(
+            query_after,
+            (
+                room_id, topological_ordering, topological_ordering,
+                stream_ordering, after_limit,
+            )
+        )
+
+        rows = self.cursor_to_dict(txn)
+        events_after = [r["event_id"] for r in rows]
+
+        if rows:
+            end_token = str(RoomStreamToken(
+                rows[-1]["topological_ordering"],
+                rows[-1]["stream_ordering"],
+            ))
+        else:
+            end_token = str(RoomStreamToken(
+                topological_ordering,
+                stream_ordering,
+            ))
+
+        return {
+            "before": {
+                "event_ids": events_before,
+                "token": start_token,
+            },
+            "after": {
+                "event_ids": events_after,
+                "token": end_token,
+            },
+        }