dendrite/roomserver/storage/shared/storage.go

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package shared
import (
"context"
"database/sql"
"encoding/json"
"fmt"
"github.com/matrix-org/dendrite/internal/sqlutil"
"github.com/matrix-org/dendrite/roomserver/api"
"github.com/matrix-org/dendrite/roomserver/storage/tables"
"github.com/matrix-org/dendrite/roomserver/types"
"github.com/matrix-org/gomatrixserverlib"
"github.com/tidwall/gjson"
)
// Ideally, when we have both events we should redact the event JSON and forget about the redaction, but we currently
// don't because the redaction code is brand new. When we are more certain that redactions don't misbehave or are
// vulnerable to attacks from remote servers (e.g a server bypassing event auth rules shouldn't redact our data)
// then we should flip this to true. This will mean redactions /actually delete information irretrievably/ which
// will be necessary for compliance with the law. Note that downstream components (syncapi) WILL delete information
// in their database on receipt of a redaction. Also note that we still modify the event JSON to set the field
// unsigned.redacted_because - we just don't clear out the content fields yet.
//
// If this hasn't been done by 09/2020 this should be flipped to true.
const redactionsArePermanent = false
type Database struct {
DB *sql.DB
Writer sqlutil.TransactionWriter
EventsTable tables.Events
EventJSONTable tables.EventJSON
EventTypesTable tables.EventTypes
EventStateKeysTable tables.EventStateKeys
RoomsTable tables.Rooms
TransactionsTable tables.Transactions
StateSnapshotTable tables.StateSnapshot
StateBlockTable tables.StateBlock
RoomAliasesTable tables.RoomAliases
PrevEventsTable tables.PreviousEvents
InvitesTable tables.Invites
MembershipTable tables.Membership
PublishedTable tables.Published
RedactionsTable tables.Redactions
}
func (d *Database) SupportsConcurrentRoomInputs() bool {
return true
}
func (d *Database) EventTypeNIDs(
ctx context.Context, eventTypes []string,
) (map[string]types.EventTypeNID, error) {
return d.EventTypesTable.BulkSelectEventTypeNID(ctx, eventTypes)
}
func (d *Database) EventStateKeys(
ctx context.Context, eventStateKeyNIDs []types.EventStateKeyNID,
) (map[types.EventStateKeyNID]string, error) {
return d.EventStateKeysTable.BulkSelectEventStateKey(ctx, eventStateKeyNIDs)
}
func (d *Database) EventStateKeyNIDs(
ctx context.Context, eventStateKeys []string,
) (map[string]types.EventStateKeyNID, error) {
return d.EventStateKeysTable.BulkSelectEventStateKeyNID(ctx, eventStateKeys)
}
func (d *Database) StateEntriesForEventIDs(
ctx context.Context, eventIDs []string,
) ([]types.StateEntry, error) {
return d.EventsTable.BulkSelectStateEventByID(ctx, eventIDs)
}
func (d *Database) StateEntriesForTuples(
ctx context.Context,
stateBlockNIDs []types.StateBlockNID,
stateKeyTuples []types.StateKeyTuple,
) ([]types.StateEntryList, error) {
return d.StateBlockTable.BulkSelectFilteredStateBlockEntries(
ctx, stateBlockNIDs, stateKeyTuples,
)
}
func (d *Database) AddState(
ctx context.Context,
roomNID types.RoomNID,
stateBlockNIDs []types.StateBlockNID,
state []types.StateEntry,
) (stateNID types.StateSnapshotNID, err error) {
err = d.Writer.Do(d.DB, nil, func(txn *sql.Tx) error {
if len(state) > 0 {
var stateBlockNID types.StateBlockNID
stateBlockNID, err = d.StateBlockTable.BulkInsertStateData(ctx, txn, state)
if err != nil {
return fmt.Errorf("d.StateBlockTable.BulkInsertStateData: %w", err)
}
stateBlockNIDs = append(stateBlockNIDs[:len(stateBlockNIDs):len(stateBlockNIDs)], stateBlockNID)
}
stateNID, err = d.StateSnapshotTable.InsertState(ctx, txn, roomNID, stateBlockNIDs)
if err != nil {
return fmt.Errorf("d.StateSnapshotTable.InsertState: %w", err)
}
return nil
})
if err != nil {
return 0, fmt.Errorf("d.Writer.Do: %w", err)
}
return
}
func (d *Database) EventNIDs(
ctx context.Context, eventIDs []string,
) (map[string]types.EventNID, error) {
return d.EventsTable.BulkSelectEventNID(ctx, eventIDs)
}
func (d *Database) SetState(
ctx context.Context, eventNID types.EventNID, stateNID types.StateSnapshotNID,
) error {
return d.Writer.Do(d.DB, nil, func(txn *sql.Tx) error {
return d.EventsTable.UpdateEventState(ctx, txn, eventNID, stateNID)
})
}
func (d *Database) StateAtEventIDs(
ctx context.Context, eventIDs []string,
) ([]types.StateAtEvent, error) {
return d.EventsTable.BulkSelectStateAtEventByID(ctx, eventIDs)
}
func (d *Database) SnapshotNIDFromEventID(
ctx context.Context, eventID string,
) (types.StateSnapshotNID, error) {
_, stateNID, err := d.EventsTable.SelectEvent(ctx, nil, eventID)
return stateNID, err
}
func (d *Database) EventIDs(
ctx context.Context, eventNIDs []types.EventNID,
) (map[types.EventNID]string, error) {
return d.EventsTable.BulkSelectEventID(ctx, eventNIDs)
}
func (d *Database) EventsFromIDs(ctx context.Context, eventIDs []string) ([]types.Event, error) {
nidMap, err := d.EventNIDs(ctx, eventIDs)
if err != nil {
return nil, err
}
var nids []types.EventNID
for _, nid := range nidMap {
nids = append(nids, nid)
}
return d.Events(ctx, nids)
}
func (d *Database) RoomNID(ctx context.Context, roomID string) (types.RoomNID, error) {
roomNID, err := d.RoomsTable.SelectRoomNID(ctx, nil, roomID)
if err == sql.ErrNoRows {
return 0, nil
}
return roomNID, err
}
func (d *Database) RoomNIDExcludingStubs(ctx context.Context, roomID string) (roomNID types.RoomNID, err error) {
roomNID, err = d.RoomNID(ctx, roomID)
if err != nil {
return
}
latestEvents, _, err := d.RoomsTable.SelectLatestEventNIDs(ctx, nil, roomNID)
if err != nil {
return
}
if len(latestEvents) == 0 {
roomNID = 0
return
}
return
}
func (d *Database) LatestEventIDs(
ctx context.Context, roomNID types.RoomNID,
) (references []gomatrixserverlib.EventReference, currentStateSnapshotNID types.StateSnapshotNID, depth int64, err error) {
var eventNIDs []types.EventNID
eventNIDs, currentStateSnapshotNID, err = d.RoomsTable.SelectLatestEventNIDs(ctx, nil, roomNID)
if err != nil {
return
}
references, err = d.EventsTable.BulkSelectEventReference(ctx, nil, eventNIDs)
if err != nil {
return
}
depth, err = d.EventsTable.SelectMaxEventDepth(ctx, nil, eventNIDs)
if err != nil {
return
}
return
}
func (d *Database) StateBlockNIDs(
ctx context.Context, stateNIDs []types.StateSnapshotNID,
) ([]types.StateBlockNIDList, error) {
return d.StateSnapshotTable.BulkSelectStateBlockNIDs(ctx, stateNIDs)
}
func (d *Database) StateEntries(
ctx context.Context, stateBlockNIDs []types.StateBlockNID,
) ([]types.StateEntryList, error) {
return d.StateBlockTable.BulkSelectStateBlockEntries(ctx, stateBlockNIDs)
}
func (d *Database) GetRoomVersionForRoom(
ctx context.Context, roomID string,
) (gomatrixserverlib.RoomVersion, error) {
return d.RoomsTable.SelectRoomVersionForRoomID(
ctx, nil, roomID,
)
}
func (d *Database) GetRoomVersionForRoomNID(
ctx context.Context, roomNID types.RoomNID,
) (gomatrixserverlib.RoomVersion, error) {
return d.RoomsTable.SelectRoomVersionForRoomNID(
ctx, roomNID,
)
}
func (d *Database) SetRoomAlias(ctx context.Context, alias string, roomID string, creatorUserID string) error {
return d.Writer.Do(d.DB, nil, func(txn *sql.Tx) error {
return d.RoomAliasesTable.InsertRoomAlias(ctx, txn, alias, roomID, creatorUserID)
})
}
func (d *Database) GetRoomIDForAlias(ctx context.Context, alias string) (string, error) {
return d.RoomAliasesTable.SelectRoomIDFromAlias(ctx, alias)
}
func (d *Database) GetAliasesForRoomID(ctx context.Context, roomID string) ([]string, error) {
return d.RoomAliasesTable.SelectAliasesFromRoomID(ctx, roomID)
}
func (d *Database) GetCreatorIDForAlias(
ctx context.Context, alias string,
) (string, error) {
return d.RoomAliasesTable.SelectCreatorIDFromAlias(ctx, alias)
}
func (d *Database) RemoveRoomAlias(ctx context.Context, alias string) error {
return d.Writer.Do(d.DB, nil, func(txn *sql.Tx) error {
return d.RoomAliasesTable.DeleteRoomAlias(ctx, txn, alias)
})
}
func (d *Database) GetMembership(
ctx context.Context, roomNID types.RoomNID, requestSenderUserID string,
) (membershipEventNID types.EventNID, stillInRoom bool, err error) {
var requestSenderUserNID types.EventStateKeyNID
err = d.Writer.Do(d.DB, nil, func(txn *sql.Tx) error {
requestSenderUserNID, err = d.assignStateKeyNID(ctx, txn, requestSenderUserID)
return err
})
if err != nil {
return 0, false, fmt.Errorf("d.assignStateKeyNID: %w", err)
}
senderMembershipEventNID, senderMembership, err :=
d.MembershipTable.SelectMembershipFromRoomAndTarget(
ctx, roomNID, requestSenderUserNID,
)
if err == sql.ErrNoRows {
// The user has never been a member of that room
return 0, false, nil
} else if err != nil {
return
}
return senderMembershipEventNID, senderMembership == tables.MembershipStateJoin, nil
}
func (d *Database) GetMembershipEventNIDsForRoom(
ctx context.Context, roomNID types.RoomNID, joinOnly bool, localOnly bool,
) ([]types.EventNID, error) {
if joinOnly {
return d.MembershipTable.SelectMembershipsFromRoomAndMembership(
ctx, roomNID, tables.MembershipStateJoin, localOnly,
)
}
return d.MembershipTable.SelectMembershipsFromRoom(ctx, roomNID, localOnly)
}
func (d *Database) GetInvitesForUser(
ctx context.Context,
roomNID types.RoomNID,
targetUserNID types.EventStateKeyNID,
) (senderUserIDs []types.EventStateKeyNID, eventIDs []string, err error) {
return d.InvitesTable.SelectInviteActiveForUserInRoom(ctx, targetUserNID, roomNID)
}
func (d *Database) Events(
ctx context.Context, eventNIDs []types.EventNID,
) ([]types.Event, error) {
eventJSONs, err := d.EventJSONTable.BulkSelectEventJSON(ctx, eventNIDs)
if err != nil {
return nil, err
}
results := make([]types.Event, len(eventJSONs))
for i, eventJSON := range eventJSONs {
var roomNID types.RoomNID
var roomVersion gomatrixserverlib.RoomVersion
result := &results[i]
result.EventNID = eventJSON.EventNID
roomNID, err = d.EventsTable.SelectRoomNIDForEventNID(ctx, eventJSON.EventNID)
if err != nil {
return nil, err
}
roomVersion, err = d.RoomsTable.SelectRoomVersionForRoomNID(ctx, roomNID)
if err != nil {
return nil, err
}
result.Event, err = gomatrixserverlib.NewEventFromTrustedJSON(
eventJSON.EventJSON, false, roomVersion,
)
if err != nil {
return nil, err
}
}
if !redactionsArePermanent {
d.applyRedactions(results)
}
return results, nil
}
func (d *Database) GetTransactionEventID(
ctx context.Context, transactionID string,
sessionID int64, userID string,
) (string, error) {
eventID, err := d.TransactionsTable.SelectTransactionEventID(ctx, transactionID, sessionID, userID)
if err == sql.ErrNoRows {
return "", nil
}
return eventID, err
}
func (d *Database) MembershipUpdater(
ctx context.Context, roomID, targetUserID string,
targetLocal bool, roomVersion gomatrixserverlib.RoomVersion,
) (*MembershipUpdater, error) {
txn, err := d.DB.Begin()
if err != nil {
return nil, err
}
var updater *MembershipUpdater
_ = d.Writer.Do(d.DB, txn, func(txn *sql.Tx) error {
updater, err = NewMembershipUpdater(ctx, d, txn, roomID, targetUserID, targetLocal, roomVersion)
return nil
})
return updater, err
}
func (d *Database) GetLatestEventsForUpdate(
ctx context.Context, roomNID types.RoomNID,
) (*LatestEventsUpdater, error) {
txn, err := d.DB.Begin()
if err != nil {
return nil, err
}
var updater *LatestEventsUpdater
_ = d.Writer.Do(d.DB, txn, func(txn *sql.Tx) error {
updater, err = NewLatestEventsUpdater(ctx, d, txn, roomNID)
return nil
})
return updater, err
}
// nolint:gocyclo
func (d *Database) StoreEvent(
ctx context.Context, event gomatrixserverlib.Event,
txnAndSessionID *api.TransactionID, authEventNIDs []types.EventNID,
) (types.RoomNID, types.StateAtEvent, *gomatrixserverlib.Event, string, error) {
var (
roomNID types.RoomNID
eventTypeNID types.EventTypeNID
eventStateKeyNID types.EventStateKeyNID
eventNID types.EventNID
stateNID types.StateSnapshotNID
redactionEvent *gomatrixserverlib.Event
redactedEventID string
err error
)
err = d.Writer.Do(d.DB, nil, func(txn *sql.Tx) error {
if txnAndSessionID != nil {
if err = d.TransactionsTable.InsertTransaction(
ctx, txn, txnAndSessionID.TransactionID,
txnAndSessionID.SessionID, event.Sender(), event.EventID(),
); err != nil {
return fmt.Errorf("d.TransactionsTable.InsertTransaction: %w", err)
}
}
// TODO: Here we should aim to have two different code paths for new rooms
// vs existing ones.
// Get the default room version. If the client doesn't supply a room_version
// then we will use our configured default to create the room.
// https://matrix.org/docs/spec/client_server/r0.6.0#post-matrix-client-r0-createroom
// Note that the below logic depends on the m.room.create event being the
// first event that is persisted to the database when creating or joining a
// room.
var roomVersion gomatrixserverlib.RoomVersion
if roomVersion, err = extractRoomVersionFromCreateEvent(event); err != nil {
return fmt.Errorf("extractRoomVersionFromCreateEvent: %w", err)
}
if roomNID, err = d.assignRoomNID(ctx, txn, event.RoomID(), roomVersion); err != nil {
return fmt.Errorf("d.assignRoomNID: %w", err)
}
if eventTypeNID, err = d.assignEventTypeNID(ctx, txn, event.Type()); err != nil {
return fmt.Errorf("d.assignEventTypeNID: %w", err)
}
eventStateKey := event.StateKey()
// Assigned a numeric ID for the state_key if there is one present.
// Otherwise set the numeric ID for the state_key to 0.
if eventStateKey != nil {
if eventStateKeyNID, err = d.assignStateKeyNID(ctx, txn, *eventStateKey); err != nil {
return fmt.Errorf("d.assignStateKeyNID: %w", err)
}
}
if eventNID, stateNID, err = d.EventsTable.InsertEvent(
ctx,
txn,
roomNID,
eventTypeNID,
eventStateKeyNID,
event.EventID(),
event.EventReference().EventSHA256,
authEventNIDs,
event.Depth(),
); err != nil {
if err == sql.ErrNoRows {
// We've already inserted the event so select the numeric event ID
eventNID, stateNID, err = d.EventsTable.SelectEvent(ctx, txn, event.EventID())
}
if err != nil {
2020-07-21 16:21:48 +00:00
return err
}
}
if err = d.EventJSONTable.InsertEventJSON(ctx, txn, eventNID, event.JSON()); err != nil {
return fmt.Errorf("d.EventJSONTable.InsertEventJSON: %w", err)
}
redactionEvent, redactedEventID, err = d.handleRedactions(ctx, txn, eventNID, event)
return nil
})
if err != nil {
return 0, types.StateAtEvent{}, nil, "", fmt.Errorf("d.Writer.Do: %w", err)
}
return roomNID, types.StateAtEvent{
BeforeStateSnapshotNID: stateNID,
StateEntry: types.StateEntry{
StateKeyTuple: types.StateKeyTuple{
EventTypeNID: eventTypeNID,
EventStateKeyNID: eventStateKeyNID,
},
EventNID: eventNID,
},
}, redactionEvent, redactedEventID, nil
}
func (d *Database) PublishRoom(ctx context.Context, roomID string, publish bool) error {
return d.Writer.Do(d.DB, nil, func(txn *sql.Tx) error {
return d.PublishedTable.UpsertRoomPublished(ctx, txn, roomID, publish)
})
}
func (d *Database) GetPublishedRooms(ctx context.Context) ([]string, error) {
return d.PublishedTable.SelectAllPublishedRooms(ctx, true)
}
func (d *Database) assignRoomNID(
ctx context.Context, txn *sql.Tx,
roomID string, roomVersion gomatrixserverlib.RoomVersion,
) (types.RoomNID, error) {
// Check if we already have a numeric ID in the database.
roomNID, err := d.RoomsTable.SelectRoomNID(ctx, txn, roomID)
if err == sql.ErrNoRows {
// We don't have a numeric ID so insert one into the database.
roomNID, err = d.RoomsTable.InsertRoomNID(ctx, txn, roomID, roomVersion)
if err == sql.ErrNoRows {
// We raced with another insert so run the select again.
roomNID, err = d.RoomsTable.SelectRoomNID(ctx, txn, roomID)
}
}
return roomNID, err
}
func (d *Database) assignEventTypeNID(
ctx context.Context, txn *sql.Tx, eventType string,
) (eventTypeNID types.EventTypeNID, err error) {
// Check if we already have a numeric ID in the database.
eventTypeNID, err = d.EventTypesTable.SelectEventTypeNID(ctx, txn, eventType)
if err == sql.ErrNoRows {
// We don't have a numeric ID so insert one into the database.
eventTypeNID, err = d.EventTypesTable.InsertEventTypeNID(ctx, txn, eventType)
if err == sql.ErrNoRows {
// We raced with another insert so run the select again.
eventTypeNID, err = d.EventTypesTable.SelectEventTypeNID(ctx, txn, eventType)
}
}
return
}
func (d *Database) assignStateKeyNID(
ctx context.Context, txn *sql.Tx, eventStateKey string,
) (types.EventStateKeyNID, error) {
// Check if we already have a numeric ID in the database.
eventStateKeyNID, err := d.EventStateKeysTable.SelectEventStateKeyNID(ctx, txn, eventStateKey)
if err == sql.ErrNoRows {
// We don't have a numeric ID so insert one into the database.
eventStateKeyNID, err = d.EventStateKeysTable.InsertEventStateKeyNID(ctx, txn, eventStateKey)
if err == sql.ErrNoRows {
// We raced with another insert so run the select again.
eventStateKeyNID, err = d.EventStateKeysTable.SelectEventStateKeyNID(ctx, txn, eventStateKey)
}
}
return eventStateKeyNID, err
}
func extractRoomVersionFromCreateEvent(event gomatrixserverlib.Event) (
gomatrixserverlib.RoomVersion, error,
) {
var err error
var roomVersion gomatrixserverlib.RoomVersion
// Look for m.room.create events.
if event.Type() != gomatrixserverlib.MRoomCreate {
return gomatrixserverlib.RoomVersion(""), nil
}
roomVersion = gomatrixserverlib.RoomVersionV1
var createContent gomatrixserverlib.CreateContent
// The m.room.create event contains an optional "room_version" key in
// the event content, so we need to unmarshal that first.
if err = json.Unmarshal(event.Content(), &createContent); err != nil {
return gomatrixserverlib.RoomVersion(""), err
}
// A room version was specified in the event content?
if createContent.RoomVersion != nil {
roomVersion = gomatrixserverlib.RoomVersion(*createContent.RoomVersion)
}
return roomVersion, err
}
// handleRedactions manages the redacted status of events. There's two cases to consider in order to comply with the spec:
// "servers should not apply or send redactions to clients until both the redaction event and original event have been seen, and are valid."
// https://matrix.org/docs/spec/rooms/v3#authorization-rules-for-events
// These cases are:
// - This is a redaction event, redact the event it references if we know about it.
// - This is a normal event which may have been previously redacted.
// In the first case, check if we have the referenced event then apply the redaction, else store it
// in the redactions table with validated=FALSE. In the second case, check if there is a redaction for it:
// if there is then apply the redactions and set validated=TRUE.
//
// When an event is redacted, the redacted event JSON is modified to add an `unsigned.redacted_because` field. We use this field
// when loading events to determine whether to apply redactions. This keeps the hot-path of reading events quick as we don't need
// to cross-reference with other tables when loading.
//
// Returns the redaction event and the event ID of the redacted event if this call resulted in a redaction.
func (d *Database) handleRedactions(
ctx context.Context, txn *sql.Tx, eventNID types.EventNID, event gomatrixserverlib.Event,
) (*gomatrixserverlib.Event, string, error) {
var err error
isRedactionEvent := event.Type() == gomatrixserverlib.MRoomRedaction && event.StateKey() == nil
if isRedactionEvent {
// an event which redacts itself should be ignored
if event.EventID() == event.Redacts() {
return nil, "", nil
}
err = d.RedactionsTable.InsertRedaction(ctx, txn, tables.RedactionInfo{
Validated: false,
RedactionEventID: event.EventID(),
RedactsEventID: event.Redacts(),
})
if err != nil {
return nil, "", err
}
}
redactionEvent, redactedEvent, validated, err := d.loadRedactionPair(ctx, txn, eventNID, event)
if err != nil {
return nil, "", err
}
if validated || redactedEvent == nil || redactionEvent == nil {
// we've seen this redaction before or there is nothing to redact
return nil, "", nil
}
if redactedEvent.RoomID() != redactionEvent.RoomID() {
// redactions across rooms aren't allowed
return nil, "", nil
}
// mark the event as redacted
err = redactedEvent.SetUnsignedField("redacted_because", redactionEvent)
if err != nil {
return nil, "", err
}
if redactionsArePermanent {
redactedEvent.Event = redactedEvent.Redact()
}
// overwrite the eventJSON table
err = d.EventJSONTable.InsertEventJSON(ctx, txn, redactedEvent.EventNID, redactedEvent.JSON())
if err != nil {
return nil, "", err
}
return &redactionEvent.Event, redactedEvent.EventID(), d.RedactionsTable.MarkRedactionValidated(ctx, txn, redactionEvent.EventID(), true)
}
// loadRedactionPair returns both the redaction event and the redacted event, else nil.
func (d *Database) loadRedactionPair(
ctx context.Context, txn *sql.Tx, eventNID types.EventNID, event gomatrixserverlib.Event,
) (*types.Event, *types.Event, bool, error) {
var redactionEvent, redactedEvent *types.Event
var info *tables.RedactionInfo
var err error
isRedactionEvent := event.Type() == gomatrixserverlib.MRoomRedaction && event.StateKey() == nil
var eventBeingRedacted string
if isRedactionEvent {
eventBeingRedacted = event.Redacts()
redactionEvent = &types.Event{
EventNID: eventNID,
Event: event,
}
} else {
eventBeingRedacted = event.EventID() // maybe, we'll see if we have info
redactedEvent = &types.Event{
EventNID: eventNID,
Event: event,
}
}
info, err = d.RedactionsTable.SelectRedactionInfoByEventBeingRedacted(ctx, txn, eventBeingRedacted)
if err != nil {
return nil, nil, false, err
}
if info == nil {
// this event hasn't been redacted or we don't have the redaction for it yet
return nil, nil, false, nil
}
if isRedactionEvent {
redactedEvent = d.loadEvent(ctx, info.RedactsEventID)
} else {
redactionEvent = d.loadEvent(ctx, info.RedactionEventID)
}
return redactionEvent, redactedEvent, info.Validated, nil
}
// applyRedactions will redact events that have an `unsigned.redacted_because` field.
func (d *Database) applyRedactions(events []types.Event) {
for i := range events {
if result := gjson.GetBytes(events[i].Unsigned(), "redacted_because"); result.Exists() {
events[i].Event = events[i].Redact()
}
}
}
// loadEvent loads a single event or returns nil on any problems/missing event
func (d *Database) loadEvent(ctx context.Context, eventID string) *types.Event {
nids, err := d.EventNIDs(ctx, []string{eventID})
if err != nil {
return nil
}
if len(nids) == 0 {
return nil
}
evs, err := d.Events(ctx, []types.EventNID{nids[eventID]})
if err != nil {
return nil
}
if len(evs) != 1 {
return nil
}
return &evs[0]
}