From 02e05e293545901f8c28bcbc38644f6e61bfa92e Mon Sep 17 00:00:00 2001
From: fiatjaf <fiatjaf@gmail.com>
Date: Mon, 6 Nov 2023 12:19:02 -0300
Subject: [PATCH] prevent saving duplicates in badger and lmdb.

---
 badger/delete.go |  1 -
 badger/save.go   | 17 +++++++++++++++++
 lmdb/save.go     | 11 +++++++++++
 3 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/badger/delete.go b/badger/delete.go
index 8c8b83d..e2d99b6 100644
--- a/badger/delete.go
+++ b/badger/delete.go
@@ -25,7 +25,6 @@ func (b *BadgerBackend) DeleteEvent(ctx context.Context, evt *nostr.Event) error
 		it := txn.NewIterator(opts)
 		it.Seek(prefix)
 		if it.ValidForPrefix(prefix) {
-			// the key is the last 32 bytes
 			idx = append(idx, it.Item().Key()[1+32:]...)
 		}
 		it.Close()
diff --git a/badger/save.go b/badger/save.go
index a2737c5..d937b6f 100644
--- a/badger/save.go
+++ b/badger/save.go
@@ -2,14 +2,31 @@ package badger
 
 import (
 	"context"
+	"encoding/hex"
 
 	"github.com/dgraph-io/badger/v4"
+	"github.com/fiatjaf/eventstore"
 	"github.com/nbd-wtf/go-nostr"
 	nostr_binary "github.com/nbd-wtf/go-nostr/binary"
 )
 
 func (b *BadgerBackend) SaveEvent(ctx context.Context, evt *nostr.Event) error {
 	return b.Update(func(txn *badger.Txn) error {
+		// query event by id to ensure we don't save duplicates
+		id, _ := hex.DecodeString(evt.ID)
+		prefix := make([]byte, 1+32)
+		copy(prefix[1:], id)
+		opts := badger.DefaultIteratorOptions
+		opts.PrefetchValues = false
+		it := txn.NewIterator(opts)
+		defer it.Close()
+		it.Seek(prefix)
+		if it.ValidForPrefix(prefix) {
+			// event exists
+			return eventstore.ErrDupEvent
+		}
+
+		// encode to binary
 		bin, err := nostr_binary.Marshal(evt)
 		if err != nil {
 			return err
diff --git a/lmdb/save.go b/lmdb/save.go
index 9eb9f4b..96e01eb 100644
--- a/lmdb/save.go
+++ b/lmdb/save.go
@@ -2,9 +2,11 @@ package lmdb
 
 import (
 	"context"
+	"encoding/hex"
 	"fmt"
 
 	"github.com/bmatsuo/lmdb-go/lmdb"
+	"github.com/fiatjaf/eventstore"
 	"github.com/nbd-wtf/go-nostr"
 	nostr_binary "github.com/nbd-wtf/go-nostr/binary"
 )
@@ -16,6 +18,15 @@ func (b *LMDBBackend) SaveEvent(ctx context.Context, evt *nostr.Event) error {
 	}
 
 	return b.lmdbEnv.Update(func(txn *lmdb.Txn) error {
+		// check if we already have this id
+		id, _ := hex.DecodeString(evt.ID)
+		_, err := txn.Get(b.indexId, id)
+		if operr, ok := err.(*lmdb.OpError); ok && operr.Errno != lmdb.NotFound {
+			// we will only proceed if we get a NotFound
+			return eventstore.ErrDupEvent
+		}
+
+		// encode to binary form so we'll save it
 		bin, err := nostr_binary.Marshal(evt)
 		if err != nil {
 			return err