f-21: code: add list prefix

Signed-off-by: GnomeZworc <nicolas.boufidjeline@g3e.fr>

pkg/db/kv/listByPrefix.go

@@ -0,0 +1,33 @@
+package kv
+
+import (
+	"github.com/dgraph-io/badger/v4"
+)
+
+// ListByPrefix returns all key-value pairs whose key starts with prefix.
+func ListByPrefix(db *badger.DB, prefix string) (map[string]string, error) {
+	result := make(map[string]string)
+	p := []byte(prefix)
+
+	err := db.View(func(txn *badger.Txn) error {
+		opts := badger.DefaultIteratorOptions
+		opts.PrefetchSize = 10
+
+		it := txn.NewIterator(opts)
+		defer it.Close()
+
+		for it.Seek(p); it.ValidForPrefix(p); it.Next() {
+			item := it.Item()
+			key := string(item.Key())
+
+			val, err := item.ValueCopy(nil)
+			if err != nil {
+				return err
+			}
+			result[key] = string(val)
+		}
+		return nil
+	})
+
+	return result, err
+}