package user

import (
	"context"
	"errors"
	"fmt"
	"time"

	"bindbox-game/internal/repository/mysql/model"

	"gorm.io/gorm"
)

// TransferCoupon 转赠优惠券给另一个用户
// fromUserID: 发送方用户ID
// toUserID: 接收方用户ID
// userCouponID: 用户持有的优惠券记录ID
func (s *service) TransferCoupon(ctx context.Context, fromUserID, toUserID, userCouponID int64) error {
	if fromUserID <= 0 || toUserID <= 0 || userCouponID <= 0 {
		return fmt.Errorf("invalid_params")
	}
	if fromUserID == toUserID {
		return fmt.Errorf("cannot_transfer_to_self")
	}

	// 1. 校验发送方持有该优惠券
	uc, err := s.readDB.UserCoupons.WithContext(ctx).
		Where(s.readDB.UserCoupons.ID.Eq(userCouponID)).
		Where(s.readDB.UserCoupons.UserID.Eq(fromUserID)).
		First()
	if err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return fmt.Errorf("coupon_not_found")
		}
		return err
	}

	// 2. 校验优惠券状态为可用
	if uc.Status != 1 {
		return fmt.Errorf("coupon_not_available")
	}

	// 3. 校验接收方用户存在
	_, err = s.readDB.Users.WithContext(ctx).Where(s.readDB.Users.ID.Eq(toUserID)).First()
	if err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return fmt.Errorf("receiver_not_found")
		}
		return err
	}

	// 4. 执行转赠：更新 user_id
	db := s.repo.GetDbW()
	err = db.Transaction(func(tx *gorm.DB) error {
		// 更新优惠券归属
		if err := tx.Model(&model.UserCoupons{}).
			Where("id = ? AND user_id = ? AND status = 1", userCouponID, fromUserID).
			Update("user_id", toUserID).Error; err != nil {
			return err
		}

		// 记录转出日志
		transferOutLog := &model.UserCouponLedger{
			UserID:       fromUserID,
			UserCouponID: userCouponID,
			ChangeAmount: 0, // 转赠不涉及金额变动
			BalanceAfter: uc.BalanceAmount,
			OrderID:      0,
			Action:       "transfer_out",
			CreatedAt:    time.Now(),
		}
		if err := tx.Create(transferOutLog).Error; err != nil {
			return err
		}

		// 记录转入日志
		transferInLog := &model.UserCouponLedger{
			UserID:       toUserID,
			UserCouponID: userCouponID,
			ChangeAmount: 0,
			BalanceAfter: uc.BalanceAmount,
			OrderID:      0,
			Action:       "transfer_in",
			CreatedAt:    time.Now(),
		}
		if err := tx.Create(transferInLog).Error; err != nil {
			return err
		}

		return nil
	})

	if err != nil {
		return err
	}

	fmt.Printf("[优惠券转赠] 成功: coupon_id=%d from=%d to=%d\n", userCouponID, fromUserID, toUserID)
	return nil
}