From 3e16bc22d6048c375bfab2f4305bbcf86f49f833 Mon Sep 17 00:00:00 2001
From: "Masaharu.Kato" <masaharu.kato@ivis.co.jp>
Date: Wed, 18 Jun 2025 11:47:25 +0900
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---
 .../todoapp/repository/ToBuysRepository.java  | 11 ++++++++++
 .../todoapp/service/ToBuysService.java        | 22 +++++++++++++++++--
 2 files changed, 31 insertions(+), 2 deletions(-)

diff --git a/backend/src/main/java/com/example/todoapp/repository/ToBuysRepository.java b/backend/src/main/java/com/example/todoapp/repository/ToBuysRepository.java
index 0778f5f..24d464f 100644
--- a/backend/src/main/java/com/example/todoapp/repository/ToBuysRepository.java
+++ b/backend/src/main/java/com/example/todoapp/repository/ToBuysRepository.java
@@ -47,6 +47,17 @@ public interface ToBuysRepository extends JpaRepository<ToBuys, Integer> {
      */
     @Query("SELECT t FROM ToBuys t WHERE t.user.id = :userId ORDER BY t.tobuyId ASC")
     List<ToBuys> findByUserIdOrderByTobuyIdAsc(@Param("userId") Long userId);
+    
+    /**
+     * 指定された「買うもの」IDに基づいて「買うもの」での数量を更新
+     *
+     * @param tobuyId 「買うもの」ID
+     * @param amount 「買うもの」数量
+     * @return 更新された行数
+     */
+    @Modifying
+    @Query("UPDATE ToBuys t SET t.amount = :amount WHERE t.tobuyId = :tobuyId")
+    int updateAmountByTobuyId(Long tobuyId, int amount);
 
     /**
      * 指定された「買うもの」IDに基づいて「買うもの」リストを削除
diff --git a/backend/src/main/java/com/example/todoapp/service/ToBuysService.java b/backend/src/main/java/com/example/todoapp/service/ToBuysService.java
index 2c0cc2a..323a447 100644
--- a/backend/src/main/java/com/example/todoapp/service/ToBuysService.java
+++ b/backend/src/main/java/com/example/todoapp/service/ToBuysService.java
@@ -171,6 +171,16 @@ public class ToBuysService {
         return toBuysRepository.findByUserIdOrderByTobuyIdAsc(user.getId());
     }
 
+    /**
+     * 指定された購入リストIDに基づいて「数量」を変更する
+     *
+     * @param tobuyId 購入リストID
+     */
+    @Transactional
+    public int updateToBuysAmountByTobuyId(Long tobuyId, int amount) {
+        return toBuysRepository.updateAmountByTobuyId(tobuyId, amount);
+    }
+
     /**
      * 指定された購入リストIDに基づいて「買うもの」を削除する
      *
@@ -207,9 +217,17 @@ public class ToBuysService {
         stock.setBuyDate(dto.getBuyDate());
         stock.setExpDate(dto.getExpDate());
 
-        // 買うものリストから削除
+        // まだ買うべき数量を計算
+        int remainAmount = Math.max(tobuy.getAmount() - dto.getAmount(), 0);
+        System.out.println("remainAmount=" + remainAmount);
+
+        // 買うものリストから削除または数量変更
         System.out.println("tobuy.getTobuyId()=" + tobuy.getTobuyId());
-        deleteToBuysByTobuyId(tobuy.getTobuyId());
+        if (remainAmount > 0) {
+            updateToBuysAmountByTobuyId(tobuy.getTobuyId(), remainAmount);
+        } else {
+            deleteToBuysByTobuyId(tobuy.getTobuyId());
+        }
 
         // データベースに保存
         return stocksRepository.save(stock);