bring in khatru and eventstore.

eventstore/lmdb/replace.go

@@ -0,0 +1,49 @@
+package lmdb
+
+import (
+	"context"
+	"fmt"
+	"math"
+
+	"github.com/PowerDNS/lmdb-go/lmdb"
+	"github.com/fiatjaf/eventstore/internal"
+	"github.com/nbd-wtf/go-nostr"
+)
+
+func (b *LMDBBackend) ReplaceEvent(ctx context.Context, evt *nostr.Event) error {
+	// sanity checking
+	if evt.CreatedAt > math.MaxUint32 || evt.Kind > math.MaxUint16 {
+		return fmt.Errorf("event with values out of expected boundaries")
+	}
+
+	return b.lmdbEnv.Update(func(txn *lmdb.Txn) error {
+		filter := nostr.Filter{Limit: 1, Kinds: []int{evt.Kind}, Authors: []string{evt.PubKey}}
+		if nostr.IsAddressableKind(evt.Kind) {
+			// when addressable, add the "d" tag to the filter
+			filter.Tags = nostr.TagMap{"d": []string{evt.Tags.GetD()}}
+		}
+
+		// now we fetch the past events, whatever they are, delete them and then save the new
+		results, err := b.query(txn, filter, 10) // in theory limit could be just 1 and this should work
+		if err != nil {
+			return fmt.Errorf("failed to query past events with %s: %w", filter, err)
+		}
+
+		shouldStore := true
+		for _, previous := range results {
+			if internal.IsOlder(previous.Event, evt) {
+				if err := b.delete(txn, previous.Event); err != nil {
+					return fmt.Errorf("failed to delete event %s for replacing: %w", previous.Event.ID, err)
+				}
+			} else {
+				// there is a newer event already stored, so we won't store this
+				shouldStore = false
+			}
+		}
+		if shouldStore {
+			return b.save(txn, evt)
+		}
+
+		return nil
+	})
+}