完善套餐与账单接口 & 完善支付数据保存，记录实付价格并关联优惠券

web/services/coupon.go

@@ -0,0 +1,64 @@
+package services
+
+import (
+	"errors"
+	"fmt"
+	"platform/web/core"
+	m "platform/web/models"
+	q "platform/web/queries"
+	"time"
+
+	"github.com/shopspring/decimal"
+	"gorm.io/gorm"
+)
+
+var Coupon = &couponService{}
+
+type couponService struct{}
+
+func (s *couponService) GetCouponAvailableByCode(code string, amount decimal.Decimal, uid *int32) (*m.Coupon, error) {
+	// 获取优惠券
+	coupon, err := q.Coupon.Where(
+		q.Coupon.Code.Eq(code),
+		q.Coupon.Status.Eq(int(m.CouponStatusUnused)),
+		q.Coupon.
+			Where(q.Coupon.ExpireAt.Gt(time.Now())).
+			Or(q.Coupon.ExpireAt.IsNull()),
+	).Take()
+	if errors.Is(err, gorm.ErrRecordNotFound) {
+		return nil, core.NewBizErr("优惠券不存在或已失效")
+	}
+	if err != nil {
+		return nil, core.NewBizErr("获取优惠券数据失败", err)
+	}
+
+	// 检查最小使用额度
+	if amount.Cmp(coupon.MinAmount) < 0 {
+		return nil, core.NewBizErr(fmt.Sprintf("使用此优惠券的最小额度为 %s", coupon.MinAmount))
+	}
+
+	// 检查所属
+	if coupon.UserID != nil {
+		if uid == nil {
+			return nil, core.NewBizErr("检查优惠券所属用户失败")
+		}
+		if *coupon.UserID != *uid {
+			return nil, core.NewBizErr("优惠券不属于当前用户")
+		}
+	}
+
+	return coupon, nil
+}
+
+func (s *couponService) UseCoupon(q *q.Query, id int32) error {
+	_, err := q.Coupon.
+		Where(
+			q.Coupon.ID.Eq(id),
+			q.Coupon.Status.Eq(int(m.CouponStatusUnused)),
+			q.Coupon.ExpireAt.Gt(time.Now()),
+		).
+		UpdateSimple(
+			q.Coupon.Status.Value(int(m.CouponStatusUsed)),
+		)
+	return err
+}