Add /_synapse/admin/v1/event_reports endpoint (#3342)

Based on #3340 

This adds a `/_synapse/admin/v1/event_reports` endpoint, the same
Synapse has. This way existing tools also work with Dendrite.
Given this is already getting huge (even though many test lines),
splitting this into two PRs. (The next adds "getting one report" and
"deleting reports")

[skip ci]

roomserver/storage/shared/storage.go

@@ -1936,6 +1936,131 @@ func (d *Database) InsertReportedEvent(
 	return reportID, err
 }
 
+// QueryAdminEventReports returns event reports given a filter.
+func (d *Database) QueryAdminEventReports(ctx context.Context, from uint64, limit uint64, backwards bool, userID string, roomID string) ([]api.QueryAdminEventReportsResponse, int64, error) {
+	// Filter on roomID, if requested
+	var roomNID types.RoomNID
+	if roomID != "" {
+		roomInfo, err := d.RoomInfo(ctx, roomID)
+		if err != nil {
+			return nil, 0, err
+		}
+		roomNID = roomInfo.RoomNID
+	}
+
+	// Same as above, but for userID
+	var userNID types.EventStateKeyNID
+	if userID != "" {
+		stateKeysMap, err := d.EventStateKeyNIDs(ctx, []string{userID})
+		if err != nil {
+			return nil, 0, err
+		}
+		if len(stateKeysMap) != 1 {
+			return nil, 0, fmt.Errorf("failed to get eventStateKeyNID for %s", userID)
+		}
+		userNID = stateKeysMap[userID]
+	}
+
+	// Query all reported events matching the filters
+	reports, count, err := d.ReportedEventsTable.SelectReportedEvents(ctx, nil, from, limit, backwards, userNID, roomNID)
+	if err != nil {
+		return nil, 0, fmt.Errorf("failed to SelectReportedEvents: %w", err)
+	}
+
+	// TODO: The below code may be inefficient due to many DB round trips and needs to be revisited.
+	// 	For the time being, this is "good enough".
+	qryRoomNIDs := make([]types.RoomNID, 0, len(reports))
+	qryEventNIDs := make([]types.EventNID, 0, len(reports))
+	qryStateKeyNIDs := make([]types.EventStateKeyNID, 0, len(reports))
+	for _, report := range reports {
+		qryRoomNIDs = append(qryRoomNIDs, report.RoomNID)
+		qryEventNIDs = append(qryEventNIDs, report.EventNID)
+		qryStateKeyNIDs = append(qryStateKeyNIDs, report.ReportingUserNID, report.SenderNID)
+	}
+
+	// This also de-dupes the roomIDs, otherwise we would query the same
+	// roomIDs in GetBulkStateContent multiple times
+	roomIDs, err := d.RoomsTable.BulkSelectRoomIDs(ctx, nil, qryRoomNIDs)
+	if err != nil {
+		return nil, 0, err
+	}
+
+	// TODO: replace this with something more efficient, as it loads the entire state snapshot.
+	stateContent, err := d.GetBulkStateContent(ctx, roomIDs, []gomatrixserverlib.StateKeyTuple{
+		{EventType: spec.MRoomName, StateKey: ""},
+		{EventType: spec.MRoomCanonicalAlias, StateKey: ""},
+	}, false)
+	if err != nil {
+		return nil, 0, err
+	}
+
+	eventIDMap, err := d.EventIDs(ctx, qryEventNIDs)
+	if err != nil {
+		logrus.WithError(err).Error("unable to map eventNIDs to eventIDs")
+		return nil, 0, err
+	}
+	if len(eventIDMap) != len(qryEventNIDs) {
+		return nil, 0, fmt.Errorf("expected %d eventIDs, got %d", len(qryEventNIDs), len(eventIDMap))
+	}
+
+	// Get a map from EventStateKeyNID to userID
+	userNIDMap, err := d.EventStateKeys(ctx, qryStateKeyNIDs)
+	if err != nil {
+		logrus.WithError(err).Error("unable to map userNIDs to userIDs")
+		return nil, 0, err
+	}
+
+	// Create a cache from roomNID to roomID to avoid hitting the DB again
+	roomNIDIDCache := make(map[types.RoomNID]string, len(roomIDs))
+	for i := 0; i < len(reports); i++ {
+		cachedRoomID := roomNIDIDCache[reports[i].RoomNID]
+		if cachedRoomID == "" {
+			// We need to query this again, as we otherwise don't have a way to match roomNID -> roomID
+			roomIDs, err = d.RoomsTable.BulkSelectRoomIDs(ctx, nil, []types.RoomNID{reports[i].RoomNID})
+			if err != nil {
+				return nil, 0, err
+			}
+			if len(roomIDs) == 0 || len(roomIDs) > 1 {
+				logrus.Warnf("unable to map roomNID %d to a roomID, was this room deleted?", roomNID)
+				continue
+			}
+			roomNIDIDCache[reports[i].RoomNID] = roomIDs[0]
+			cachedRoomID = roomIDs[0]
+		}
+
+		reports[i].EventID = eventIDMap[reports[i].EventNID]
+		reports[i].RoomID = cachedRoomID
+		roomName, canonicalAlias := findRoomNameAndCanonicalAlias(stateContent, cachedRoomID)
+		reports[i].RoomName = roomName
+		reports[i].CanonicalAlias = canonicalAlias
+		reports[i].Sender = userNIDMap[reports[i].SenderNID]
+		reports[i].UserID = userNIDMap[reports[i].ReportingUserNID]
+	}
+
+	return reports, count, nil
+}
+
+// findRoomNameAndCanonicalAlias loops over events to find the corresponding room name and canonicalAlias
+// for a given roomID.
+func findRoomNameAndCanonicalAlias(events []tables.StrippedEvent, roomID string) (name, canonicalAlias string) {
+	for _, ev := range events {
+		if ev.RoomID != roomID {
+			continue
+		}
+		if ev.EventType == spec.MRoomName {
+			name = ev.ContentValue
+		}
+		if ev.EventType == spec.MRoomCanonicalAlias {
+			canonicalAlias = ev.ContentValue
+		}
+		// We found both wanted values, break the loop
+		if name != "" && canonicalAlias != "" {
+			break
+		}
+	}
+	return name, canonicalAlias
+}
+
 // FIXME TODO: Remove all this - horrible dupe with roomserver/state. Can't use the original impl because of circular loops
 // it should live in this package!