bring in khatru and eventstore.

eventstore/mmm/delete.go

@@ -0,0 +1,78 @@
+package mmm
+
+import (
+	"context"
+	"encoding/binary"
+	"encoding/hex"
+	"fmt"
+	"slices"
+
+	"github.com/PowerDNS/lmdb-go/lmdb"
+	"github.com/nbd-wtf/go-nostr"
+)
+
+func (il *IndexingLayer) DeleteEvent(ctx context.Context, evt *nostr.Event) error {
+	return il.mmmm.lmdbEnv.Update(func(mmmtxn *lmdb.Txn) error {
+		return il.lmdbEnv.Update(func(iltxn *lmdb.Txn) error {
+			return il.delete(mmmtxn, iltxn, evt)
+		})
+	})
+}
+
+func (il *IndexingLayer) delete(mmmtxn *lmdb.Txn, iltxn *lmdb.Txn, evt *nostr.Event) error {
+	zeroRefs := false
+	b := il.mmmm
+
+	b.Logger.Debug().Str("layer", il.name).Uint16("il", il.id).Msg("deleting")
+
+	// first in the mmmm txn we check if we have the event still
+	idPrefix8, _ := hex.DecodeString(evt.ID[0 : 8*2])
+	val, err := mmmtxn.Get(b.indexId, idPrefix8)
+	if err != nil {
+		if lmdb.IsNotFound(err) {
+			// we already do not have this anywhere
+			return nil
+		}
+		return fmt.Errorf("failed to check if we have the event %x: %w", idPrefix8, err)
+	}
+
+	// we have this, but do we have it in the current layer?
+	// val is [posb][il_idx][il_idx...]
+	pos := positionFromBytes(val[0:12])
+
+	// check references
+	currentLayer := binary.BigEndian.AppendUint16(nil, il.id)
+	for i := 12; i < len(val); i += 2 {
+		if slices.Equal(val[i:i+2], currentLayer) {
+			// we will remove the current layer if it's found
+			nextval := make([]byte, len(val)-2)
+			copy(nextval, val[0:i])
+			copy(nextval[i:], val[i+2:])
+
+			if err := mmmtxn.Put(b.indexId, idPrefix8, nextval, 0); err != nil {
+				return fmt.Errorf("failed to update references for %x: %w", idPrefix8, err)
+			}
+
+			// if there are no more layers we will delete everything later
+			zeroRefs = len(nextval) == 12
+
+			break
+		}
+	}
+
+	// calculate all index keys we have for this event and delete them
+	for k := range il.getIndexKeysForEvent(evt) {
+		if err := iltxn.Del(k.dbi, k.key, val[0:12]); err != nil && !lmdb.IsNotFound(err) {
+			return fmt.Errorf("index entry %v/%x deletion failed: %w", k.dbi, k.key, err)
+		}
+	}
+
+	// if there are no more refs we delete the event from the id index and mmap
+	if zeroRefs {
+		if err := b.purge(mmmtxn, idPrefix8, pos); err != nil {
+			panic(err)
+		}
+	}
+
+	return nil
+}