sdk: use a prefix iterator on kvdb for storing relay urls associated with ids.

sdk/kvstore/badger/store.go

@@ -57,3 +57,28 @@ func (s *Store) Delete(key []byte) error {
 func (s *Store) Close() error {
 	return s.db.Close()
 }
+
+func (s *Store) Scan(prefix []byte, fn func(key []byte, value []byte) bool) error {
+	return s.db.View(func(txn *badger.Txn) error {
+		it := txn.NewIterator(badger.DefaultIteratorOptions)
+		defer it.Close()
+
+		for it.Seek(prefix); it.ValidForPrefix(prefix); it.Next() {
+			item := it.Item()
+			err := item.Value(func(v []byte) error {
+				k := item.Key()
+				if !fn(k, v) {
+					return badger.ErrStopIteration
+				}
+				return nil
+			})
+			if err == badger.ErrStopIteration {
+				break
+			}
+			if err != nil {
+				return err
+			}
+		}
+		return nil
+	})
+}

sdk/kvstore/interface.go

@@ -13,4 +13,8 @@ type KVStore interface {
 	
 	// Close releases any resources held by the store
 	Close() error
+
+	// Scan iterates through all keys with the given prefix.
+	// For each key-value pair, fn is called. If fn returns false, iteration stops.
+	Scan(prefix []byte, fn func(key []byte, value []byte) bool) error
 }

sdk/kvstore/lmdb/store.go

@@ -90,3 +90,23 @@ func (s *Store) Close() error {
 	s.env.Close()
 	return nil
 }
+
+func (s *Store) Scan(prefix []byte, fn func(key []byte, value []byte) bool) error {
+	return s.env.View(func(txn *lmdb.Txn) error {
+		cursor, err := txn.OpenCursor(s.dbi)
+		if err != nil {
+			return err
+		}
+		defer cursor.Close()
+
+		for k, v, err := cursor.Get(prefix, nil, lmdb.SetRange); err == nil; k, v, err = cursor.Get(nil, nil, lmdb.Next) {
+			if !bytes.HasPrefix(k, prefix) {
+				break
+			}
+			if !fn(k, v) {
+				break
+			}
+		}
+		return nil
+	})
+}

sdk/kvstore/memory/store.go

@@ -56,3 +56,18 @@ func (s *Store) Close() error {
 	s.data = nil
 	return nil
 }
+
+func (s *Store) Scan(prefix []byte, fn func(key []byte, value []byte) bool) error {
+	s.RLock()
+	defer s.RUnlock()
+
+	prefixStr := string(prefix)
+	for k, v := range s.data {
+		if strings.HasPrefix(k, prefixStr) {
+			if !fn([]byte(k), v) {
+				break
+			}
+		}
+	}
+	return nil
+}

sdk/system.go

@@ -139,6 +139,33 @@ func (sys *System) Close() {
 	}
 }
 
+// GetEventRelays returns all known relay URLs that have been seen to carry the given event.
+func (sys *System) GetEventRelays(eventID string) ([]string, error) {
+	// decode the event ID hex into bytes
+	idBytes, err := hex.DecodeString(eventID)
+	if err != nil || len(idBytes) < 8 {
+		return nil, fmt.Errorf("invalid event id")
+	}
+
+	// create prefix for scanning: 'r' + first 8 bytes of event ID
+	prefix := make([]byte, 9)
+	prefix[0] = eventRelayPrefix
+	copy(prefix[1:], idBytes[:8])
+
+	relays := make([]string, 0)
+	err = sys.KVStore.Scan(prefix, func(key []byte, value []byte) bool {
+		// extract relay URL from key (everything after prefix)
+		relay := string(key[9:])
+		relays = append(relays, relay)
+		return true
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	return relays, nil
+}
+
 func WithHintsDB(hdb hints.HintsDB) SystemModifier {
 	return func(sys *System) {
 		sys.Hints = hdb

sdk/tracker.go

@@ -110,6 +110,17 @@ func (sys *System) TrackEventHints(ie nostr.RelayEvent) {
 	}
 }
 
+const eventRelayPrefix = byte('r')
+
+func makeEventRelayKey(eventID []byte, relay string) []byte {
+	// Format: 'r' + first 8 bytes of event ID + relay URL
+	key := make([]byte, 1+8+len(relay))
+	key[0] = eventRelayPrefix
+	copy(key[1:], eventID[:8])
+	copy(key[9:], relay)
+	return key
+}
+
 func (sys *System) TrackEventRelays(ie nostr.RelayEvent) {
 	// decode the event ID hex into bytes
 	idBytes, err := hex.DecodeString(ie.ID)
@@ -117,11 +128,9 @@ func (sys *System) TrackEventRelays(ie nostr.RelayEvent) {
 		return
 	}
 
-	// store only first 8 bytes of event ID as key
-	key := idBytes[:8]
-
-	// store the relay URL as value
-	sys.KVStore.Set(key, []byte(ie.Relay.URL))
+	// store with prefix + eventid + relay format
+	key := makeEventRelayKey(idBytes, ie.Relay.URL)
+	sys.KVStore.Set(key, nil) // value is not needed since relay is in key
 }
 
 func (sys *System) TrackEventRelaysD(relay, id string) {
@@ -131,9 +140,7 @@ func (sys *System) TrackEventRelaysD(relay, id string) {
 		return
 	}
 
-	// store only first 8 bytes of event ID as key
-	key := idBytes[:8]
-
-	// store the relay URL as value
-	sys.KVStore.Set(key, []byte(relay))
+	// store with prefix + eventid + relay format
+	key := makeEventRelayKey(idBytes, relay)
+	sys.KVStore.Set(key, nil) // value is not needed since relay is in key
 }