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
}