Implement client single event retrieval (#693)

3 files changed, 138 insertions, 0 deletions

diff --git a/clientapi/routing/getevent.go b/clientapi/routing/getevent.go
new file mode 100644
index 00000000..7071d16f
--- /dev/null
+++ b/clientapi/routing/getevent.go
@@ -0,0 +1,127 @@
+// Copyright 2019 Alex Chen
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package routing
+
+import (
+	"net/http"
+
+	"github.com/matrix-org/dendrite/clientapi/auth/authtypes"
+	"github.com/matrix-org/dendrite/clientapi/httputil"
+	"github.com/matrix-org/dendrite/clientapi/jsonerror"
+	"github.com/matrix-org/dendrite/common/config"
+	"github.com/matrix-org/dendrite/roomserver/api"
+	"github.com/matrix-org/gomatrixserverlib"
+	"github.com/matrix-org/util"
+)
+
+type getEventRequest struct {
+	req            *http.Request
+	device         *authtypes.Device
+	roomID         string
+	eventID        string
+	cfg            config.Dendrite
+	federation     *gomatrixserverlib.FederationClient
+	keyRing        gomatrixserverlib.KeyRing
+	requestedEvent gomatrixserverlib.Event
+}
+
+// GetEvent implements GET /_matrix/client/r0/rooms/{roomId}/event/{eventId}
+// https://matrix.org/docs/spec/client_server/r0.4.0.html#get-matrix-client-r0-rooms-roomid-event-eventid
+func GetEvent(
+	req *http.Request,
+	device *authtypes.Device,
+	roomID string,
+	eventID string,
+	cfg config.Dendrite,
+	queryAPI api.RoomserverQueryAPI,
+	federation *gomatrixserverlib.FederationClient,
+	keyRing gomatrixserverlib.KeyRing,
+) util.JSONResponse {
+	eventsReq := api.QueryEventsByIDRequest{
+		EventIDs: []string{eventID},
+	}
+	var eventsResp api.QueryEventsByIDResponse
+	err := queryAPI.QueryEventsByID(req.Context(), &eventsReq, &eventsResp)
+	if err != nil {
+		return httputil.LogThenError(req, err)
+	}
+
+	if len(eventsResp.Events) == 0 {
+		// Event not found locally
+		return util.JSONResponse{
+			Code: http.StatusNotFound,
+			JSON: jsonerror.NotFound("The event was not found or you do not have permission to read this event"),
+		}
+	}
+
+	requestedEvent := eventsResp.Events[0]
+
+	r := getEventRequest{
+		req:            req,
+		device:         device,
+		roomID:         roomID,
+		eventID:        eventID,
+		cfg:            cfg,
+		federation:     federation,
+		keyRing:        keyRing,
+		requestedEvent: requestedEvent,
+	}
+
+	stateReq := api.QueryStateAfterEventsRequest{
+		RoomID:       r.requestedEvent.RoomID(),
+		PrevEventIDs: r.requestedEvent.PrevEventIDs(),
+		StateToFetch: []gomatrixserverlib.StateKeyTuple{{
+			EventType: gomatrixserverlib.MRoomMember,
+			StateKey:  device.UserID,
+		}},
+	}
+	var stateResp api.QueryStateAfterEventsResponse
+	if err := queryAPI.QueryStateAfterEvents(req.Context(), &stateReq, &stateResp); err != nil {
+		return httputil.LogThenError(req, err)
+	}
+
+	if !stateResp.RoomExists {
+		util.GetLogger(req.Context()).Errorf("Expected to find room for event %s but failed", r.requestedEvent.EventID())
+		return jsonerror.InternalServerError()
+	}
+
+	if !stateResp.PrevEventsExist {
+		// Missing some events locally; stateResp.StateEvents unavailable.
+		return util.JSONResponse{
+			Code: http.StatusNotFound,
+			JSON: jsonerror.NotFound("The event was not found or you do not have permission to read this event"),
+		}
+	}
+
+	for _, stateEvent := range stateResp.StateEvents {
+		if stateEvent.StateKeyEquals(r.device.UserID) {
+			membership, err := stateEvent.Membership()
+			if err != nil {
+				return httputil.LogThenError(req, err)
+			}
+			if membership == gomatrixserverlib.Join {
+				return util.JSONResponse{
+					Code: http.StatusOK,
+					JSON: gomatrixserverlib.ToClientEvent(r.requestedEvent, gomatrixserverlib.FormatAll),
+				}
+			}
+		}
+	}
+
+	return util.JSONResponse{
+		Code: http.StatusNotFound,
+		JSON: jsonerror.NotFound("The event was not found or you do not have permission to read this event"),
+	}
+}
diff --git a/clientapi/routing/routing.go b/clientapi/routing/routing.go
index 825dd97a..d36ed695 100644
--- a/clientapi/routing/routing.go
+++ b/clientapi/routing/routing.go
@@ -132,6 +132,15 @@ func Setup(
 				nil, cfg, queryAPI, producer, transactionsCache)
 		}),
 	).Methods(http.MethodPut, http.MethodOptions)
+	r0mux.Handle("/rooms/{roomID}/event/{eventID}",
+		common.MakeAuthAPI("rooms_get_event", authData, func(req *http.Request, device *authtypes.Device) util.JSONResponse {
+			vars, err := common.URLDecodeMapValues(mux.Vars(req))
+			if err != nil {
+				return util.ErrorResponse(err)
+			}
+			return GetEvent(req, device, vars["roomID"], vars["eventID"], cfg, queryAPI, federation, keyRing)
+		}),
+	).Methods(http.MethodGet, http.MethodOptions)
 	r0mux.Handle("/rooms/{roomID}/state/{eventType:[^/]+/?}",
 		common.MakeAuthAPI("send_message", authData, func(req *http.Request, device *authtypes.Device) util.JSONResponse {
 			vars, err := common.URLDecodeMapValues(mux.Vars(req))
diff --git a/testfile b/testfile
index 74c9d9e4..d04ab731 100644
--- a/testfile
+++ b/testfile
@@ -168,3 +168,5 @@ Newly updated tags appear in an incremental v2 /sync
 Deleted tags appear in an incremental v2 /sync
 /event/ on non world readable room does not work
 Outbound federation can query profile data
+/event/ on joined room works
+/event/ does not allow access to events before the user joined