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
+}