From 67b681d1ddc0c5f7d3a4a489d8b60b672c851db8 Mon Sep 17 00:00:00 2001
From: ZhuangYumin <zhuangyumin@sjtu.edu.cn>
Date: Thu, 14 Dec 2023 04:02:52 +0000
Subject: [PATCH] upd: add check for ISBN before change ISBN

---
 backend/src/engine.cpp | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/backend/src/engine.cpp b/backend/src/engine.cpp
index 5a5cacf..d97206f 100644
--- a/backend/src/engine.cpp
+++ b/backend/src/engine.cpp
@@ -314,6 +314,8 @@ std::vector<std::string> BookStoreEngineClass::ExecuteMOdify(
   if (login_stack.top().second == "" || login_stack.top().second == new_ISBN)
     return std::vector<std::string>({"Invalid"});
   // debugPrint("successfully checked ISBN");
+  if (new_ISBN != "" && book_data_base.HaveISBN(new_ISBN))
+    return std::vector<std::string>({"Invalid"});
   if (keyword != "") {
     std::vector<std::string> key_list;
     if (!KeyWordSpliter(keyword, key_list, false))