fix(coupon): 修复订单取消时金额券未退还的bug

订单取消退券逻辑依赖 used_order_id 匹配，但金额券在下单时
不设置 used_order_id（仅在支付确认后设置），导致未支付订单
取消时 WHERE 条件匹配不到行，退券静默失败。

修复：去掉 used_order_id 条件，按券 ID 直接退还，增加幂等
校验和错误处理，兜底从流水回推预扣金额。

internal/service/user/orders_action.go

@@ -59,32 +59,66 @@ func (s *service) CancelOrder(ctx context.Context, userID int64, orderID int64,
 
 		// 4. 退还优惠券（恢复预扣的余额和状态）
 		if order.CouponID > 0 {
-			var oc struct {
+			// 幂等校验：若已记录过 cancel_refund 流水则跳过
-				AppliedAmount int64
+			refundExists, err := tx.UserCouponLedger.WithContext(ctx).Where(
+				tx.UserCouponLedger.UserCouponID.Eq(order.CouponID),
+				tx.UserCouponLedger.OrderID.Eq(order.ID),
+				tx.UserCouponLedger.Action.Eq("cancel_refund"),
+			).Count()
+			if err != nil {
+				return err
 			}
-			// 获取该订单实际扣减的优惠券金额
-			_ = tx.OrderCoupons.WithContext(ctx).Where(tx.OrderCoupons.OrderID.Eq(order.ID), tx.OrderCoupons.UserCouponID.Eq(order.CouponID)).Scan(&oc)
 
-			// 执行原子回退：增加余额 + 重置状态 + 清除占用订单
+			if refundExists == 0 {
-			res := tx.UserCoupons.WithContext(ctx).UnderlyingDB().Exec(`
+				var oc struct {
-				UPDATE user_coupons 
+					AppliedAmount int64
-				SET balance_amount = balance_amount + ?,
+				}
-					status = 1,
+				// 优先从 order_coupons 获取实际抵扣金额
-					used_order_id = 0,
+				if err := tx.OrderCoupons.WithContext(ctx).Where(
-					used_at = NULL
+					tx.OrderCoupons.OrderID.Eq(order.ID),
-				WHERE id = ? AND used_order_id = ?
+					tx.OrderCoupons.UserCouponID.Eq(order.CouponID),
-			`, oc.AppliedAmount, order.CouponID, order.ID)
+				).Scan(&oc); err != nil {
+					return err
+				}
 
-			if res.RowsAffected > 0 {
+				// 兜底：order_coupons 无记录时，从流水中回推预扣金额
-				// 记录退还流水
+				if oc.AppliedAmount <= 0 {
-				_ = tx.UserCouponLedger.WithContext(ctx).Create(&model.UserCouponLedger{
+					if err := tx.UserCouponLedger.WithContext(ctx).UnderlyingDB().Raw(`
-					UserID:       userID,
+						SELECT COALESCE(SUM(CASE WHEN change_amount < 0 THEN -change_amount ELSE 0 END), 0) AS applied_amount
-					UserCouponID: order.CouponID,
+						FROM user_coupon_ledger
-					ChangeAmount: oc.AppliedAmount,
+						WHERE user_id = ? AND user_coupon_id = ? AND order_id = ? AND action IN ('reserve', 'usage')
-					OrderID:      order.ID,
+					`, userID, order.CouponID, order.ID).Scan(&oc).Error; err != nil {
-					Action:       "cancel_refund",
+						return err
-					CreatedAt:    time.Now(),
+					}
-				})
+				}
+
+				if oc.AppliedAmount > 0 {
+					// 恢复余额 + 重置状态（不依赖 used_order_id）
+					res := tx.UserCoupons.WithContext(ctx).UnderlyingDB().Exec(`
+						UPDATE user_coupons
+						SET balance_amount = balance_amount + ?,
+							status = 1,
+							used_order_id = 0,
+							used_at = NULL
+						WHERE id = ?
+					`, oc.AppliedAmount, order.CouponID)
+					if res.Error != nil {
+						return res.Error
+					}
+
+					if res.RowsAffected > 0 {
+						if err := tx.UserCouponLedger.WithContext(ctx).Create(&model.UserCouponLedger{
+							UserID:       userID,
+							UserCouponID: order.CouponID,
+							ChangeAmount: oc.AppliedAmount,
+							OrderID:      order.ID,
+							Action:       "cancel_refund",
+							CreatedAt:    time.Now(),
+						}); err != nil {
+							return err
+						}
+					}
+				}
 			}
 		}