package services

import (
	"errors"
	"fmt"
	"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.Find()
}

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

func (s *couponService) Create(data CreateCouponData) error {
	return q.Coupon.Create(&m.Coupon{
		UserID:    data.UserID,
		Code:      data.Code,
		Remark:    data.Remark,
		Amount:    data.Amount,
		MinAmount: data.MinAmount,
		Status:    m.CouponStatusUnused,
		ExpireAt:  data.ExpireAt,
	})
}

type CreateCouponData struct {
	UserID    *int32          `json:"user_id"`
	Code      string          `json:"code" validate:"required"`
	Remark    *string         `json:"remark"`
	Amount    decimal.Decimal `json:"amount" validate:"required"`
	MinAmount decimal.Decimal `json:"min_amount"`
	ExpireAt  *time.Time      `json:"expire_at"`
}

func (s *couponService) Update(data UpdateCouponData) error {
	do := make([]field.AssignExpr, 0)

	if data.UserID != nil {
		do = append(do, q.Coupon.UserID.Value(*data.UserID))
	}
	if data.Code != nil {
		do = append(do, q.Coupon.Code.Value(*data.Code))
	}
	if data.Remark != nil {
		do = append(do, q.Coupon.Remark.Value(*data.Remark))
	}
	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.Status != nil {
		do = append(do, q.Coupon.Status.Value(int(*data.Status)))
	}
	if data.ExpireAt != nil {
		do = append(do, q.Coupon.ExpireAt.Value(*data.ExpireAt))
	}

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

type UpdateCouponData struct {
	ID        int32            `json:"id" validate:"required"`
	UserID    *int32           `json:"user_id"`
	Code      *string          `json:"code"`
	Remark    *string          `json:"remark"`
	Amount    *decimal.Decimal `json:"amount"`
	MinAmount *decimal.Decimal `json:"min_amount"`
	Status    *m.CouponStatus  `json:"status"`
	ExpireAt  *time.Time       `json:"expire_at"`
}

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

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
}