package services

import (
	"errors"
	"fmt"
	"platform/pkg/u"
	"platform/web/core"
	m "platform/web/models"
	q "platform/web/queries"
	"time"

	"github.com/shopspring/decimal"
	"gorm.io/gen/field"
	"gorm.io/gorm"
)

var Coupon = &couponService{}

type couponService struct{}

func (s *couponService) All() (result []*m.Coupon, err error) {
	return q.Coupon.Order(q.Coupon.CreatedAt.Desc()).Find()
}

func (s *couponService) Page(req *core.PageReq) (result []*m.Coupon, count int64, err error) {
	return q.Coupon.Order(q.Coupon.CreatedAt.Desc()).FindByPage(req.GetOffset(), req.GetLimit())
}

func (s *couponService) Create(data CreateCouponData) error {
	return q.Coupon.Create(&m.Coupon{
		Name:       data.Name,
		Amount:     data.Amount,
		MinAmount:  data.MinAmount,
		Count:      int32(u.Else(data.Count, 1)),
		Status:     u.Else(data.Status, m.CouponStatusEnabled),
		ExpireType: u.Else(data.ExpireType, m.CouponExpireTypeNever),
		ExpireAt:   data.ExpireAt,
		ExpireIn:   data.ExpireIn,
	})
}

type CreateCouponData struct {
	Name       string              `json:"name" validate:"required"`
	Amount     decimal.Decimal     `json:"amount" validate:"required"`
	MinAmount  decimal.Decimal     `json:"min_amount"`
	Count      *int                `json:"count"`
	Status     *m.CouponStatus     `json:"status"`
	ExpireType *m.CouponExpireType `json:"expire_type"`
	ExpireAt   *time.Time          `json:"expire_at"`
	ExpireIn   *int                `json:"expire_in"`
}

func (s *couponService) Update(data UpdateCouponData) error {
	do := make([]field.AssignExpr, 0)
	if data.Name != nil {
		do = append(do, q.Coupon.Name.Value(*data.Name))
	}
	if data.Amount != nil {
		do = append(do, q.Coupon.Amount.Value(*data.Amount))
	}
	if data.MinAmount != nil {
		do = append(do, q.Coupon.MinAmount.Value(*data.MinAmount))
	}
	if data.Count != nil {
		do = append(do, q.Coupon.Count_.Value(int32(*data.Count)))
	}
	if data.Status != nil {
		do = append(do, q.Coupon.Status.Value(int(*data.Status)))
	}
	if data.ExpireType != nil {
		do = append(do, q.Coupon.ExpireType.Value(int(*data.ExpireType)))
	}
	if data.ExpireAt != nil {
		do = append(do, q.Coupon.ExpireAt.Value(*data.ExpireAt))
	}
	if data.ExpireIn != nil {
		do = append(do, q.Coupon.ExpireIn.Value(*data.ExpireIn))
	}

	_, err := q.Coupon.Where(q.Coupon.ID.Eq(data.ID)).UpdateSimple(do...)
	return err
}

type UpdateCouponData struct {
	ID         int32               `json:"id" validate:"required"`
	Name       *string             `json:"name"`
	Amount     *decimal.Decimal    `json:"amount"`
	MinAmount  *decimal.Decimal    `json:"min_amount"`
	Count      *int                `json:"count"`
	Status     *m.CouponStatus     `json:"status"`
	ExpireType *m.CouponExpireType `json:"expire_type"`
	ExpireAt   *time.Time          `json:"expire_at"`
	ExpireIn   *int                `json:"expire_in"`
}

func (s *couponService) Delete(id int32) error {
	_, err := q.Coupon.Where(q.Coupon.ID.Eq(id)).UpdateColumn(q.Coupon.DeletedAt, time.Now())
	return err
}

// GetUserCoupon 获取用户的指定优惠券
func (s *couponService) GetUserCoupon(uid int32, cuid int32, amount decimal.Decimal) (*m.CouponUser, error) {
	// 获取优惠券
	assigned, err := q.CouponUser.Joins(q.CouponUser.Coupon).Where(
		q.CouponUser.ID.Eq(cuid),
		q.CouponUser.UserID.Eq(uid),
		q.CouponUser.Status.Eq(int(m.CouponUserStatusUnused)),
		q.CouponUser.ExpireAt.Gt(time.Now()),
	).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(assigned.Coupon.MinAmount) < 0 {
		return nil, core.NewBizErr(fmt.Sprintf("使用此优惠券的最小额度为 %s", assigned.Coupon.MinAmount))
	}

	return assigned, nil
}

func (s *couponService) UseCoupon(q *q.Query, cuid int32) error {
	_, err := q.CouponUser.
		Where(
			q.CouponUser.ID.Eq(cuid),
			q.CouponUser.Status.Eq(int(m.CouponUserStatusUnused)),
		).
		UpdateSimple(
			q.CouponUser.Status.Value(int(m.CouponUserStatusUsed)),
			q.CouponUser.UsedAt.Value(time.Now()),
		)
	return err
}