Implement /state endpoint

src/github.com/matrix-org/dendrite/syncapi/routing/routing.go

@@ -33,4 +33,9 @@ func Setup(apiMux *mux.Router, srp *sync.RequestPool, deviceDB *devices.Database
 	r0mux.Handle("/sync", common.MakeAuthAPI("sync", deviceDB, func(req *http.Request, device *authtypes.Device) util.JSONResponse {
 		return srp.OnIncomingSyncRequest(req, device)
 	})).Methods("GET")
+
+	r0mux.Handle("/rooms/{roomID}/state", common.MakeAuthAPI("room_state", deviceDB, func(req *http.Request, device *authtypes.Device) util.JSONResponse {
+		vars := mux.Vars(req)
+		return srp.OnIncomingStateRequest(req, vars["roomID"])
+	}))
 }

src/github.com/matrix-org/dendrite/syncapi/storage/syncserver.go

@@ -162,6 +162,16 @@ func (d *SyncServerDatabase) GetStateEvent(
 	return d.roomstate.selectStateEvent(ctx, evType, roomID, stateKey)
 }
 
+func (d *SyncServerDatabase) GetStateEventsForRoom(
+	ctx context.Context, roomID string,
+) (stateEvents []gomatrixserverlib.Event, err error) {
+	err = common.WithTransaction(d.db, func(txn *sql.Tx) error {
+		stateEvents, err = d.roomstate.selectCurrentState(ctx, txn, roomID)
+		return err
+	})
+	return
+}
+
 // SyncStreamPosition returns the latest position in the sync stream. Returns 0 if there are no events yet.
 func (d *SyncServerDatabase) SyncStreamPosition(ctx context.Context) (types.StreamPosition, error) {
 	return d.syncStreamPositionTx(ctx, nil)

src/github.com/matrix-org/dendrite/syncapi/sync/requestpool.go

@@ -15,6 +15,8 @@
 package sync
 
 import (
+	"encoding/json"
+	"fmt"
 	"net/http"
 	"time"
 
@@ -105,6 +107,48 @@ func (rp *RequestPool) OnIncomingSyncRequest(req *http.Request, device *authtype
 	}
 }
 
+type stateEventInResp struct {
+	gomatrixserverlib.ClientEvent
+	PrevContent   json.RawMessage `json:"prev_content,omitempty"`
+	ReplacesState string          `json:"replaces_state,omitempty"`
+}
+
+func (rp *RequestPool) OnIncomingStateRequest(req *http.Request, roomID string) util.JSONResponse {
+	stateEvents, err := rp.db.GetStateEventsForRoom(req.Context(), roomID)
+	if err != nil {
+		return httputil.LogThenError(req, err)
+	}
+
+	resp := []stateEventInResp{}
+	// Fill the prev_content and replaces_state keys if necessary
+	for _, event := range stateEvents {
+		stateEvent := stateEventInResp{ClientEvent: gomatrixserverlib.ToClientEvent(event, gomatrixserverlib.FormatAll)}
+		var prevEventRef types.PrevEventRef
+		fmt.Println(len(event.Unsigned()))
+		if len(event.Unsigned()) > 0 {
+			if err := json.Unmarshal(event.Unsigned(), &prevEventRef); err != nil {
+				return httputil.LogThenError(req, err)
+			}
+			// Fills the previous state event ID if the state event replaces another
+			// state event
+			if len(prevEventRef.ReplacesState) > 0 {
+				stateEvent.ReplacesState = prevEventRef.ReplacesState
+			}
+			// Fill the previous event if the state event references a previous event
+			if prevEventRef.PrevContent != nil {
+				stateEvent.PrevContent = prevEventRef.PrevContent
+			}
+		}
+
+		resp = append(resp, stateEvent)
+	}
+
+	return util.JSONResponse{
+		Code: 200,
+		JSON: resp,
+	}
+}
+
 func (rp *RequestPool) currentSyncForUser(req syncRequest, currentPos types.StreamPosition) (*types.Response, error) {
 	// TODO: handle ignored users
 	if req.since == types.StreamPosition(0) {