pay-bridge/backend/internal/service/service_fee.go

package service

import (
	"context"
	"fmt"
	"log/slog"
	"math"

	"pay-bridge/internal/channel"
	"pay-bridge/internal/model"
	"pay-bridge/internal/repository"
)

// ServiceFeeService 服务费服务
type ServiceFeeService struct {
	feeRepo    *repository.ServiceFeeRepository
	tradeRepo  *repository.TradeOrderRepository
	channelSvc *ChannelService
}

func NewServiceFeeService(
	feeRepo *repository.ServiceFeeRepository,
	tradeRepo *repository.TradeOrderRepository,
	channelSvc *ChannelService,
) *ServiceFeeService {
	return &ServiceFeeService{
		feeRepo:    feeRepo,
		tradeRepo:  tradeRepo,
		channelSvc: channelSvc,
	}
}

// ChargeServiceFee 交易完成后扣收服务费
func (s *ServiceFeeService) ChargeServiceFee(ctx context.Context, tradeNo string) error {
	order, err := s.tradeRepo.GetByTradeNo(ctx, tradeNo)
	if err != nil || order == nil {
		return fmt.Errorf("order not found: %s", tradeNo)
	}

	// 幂等检查
	existing, err := s.feeRepo.GetLog(ctx, tradeNo, "CHARGE")
	if err != nil {
		return err
	}
	if existing != nil {
		return nil // 已扣收
	}

	// 获取服务费配置
	group := model.PayMethodToGroup(order.PayMethod)
	cfg, err := s.feeRepo.GetConfig(ctx, order.AppID, group)
	if err != nil {
		return err
	}
	if cfg == nil || cfg.FeeRate == 0 {
		return nil // 未配置或费率为0
	}

	// 计算服务费（四舍五入到分）
	feeAmount := calculateFee(order.Amount, cfg.FeeRate)
	if feeAmount <= 0 {
		return nil // 不足1分不扣收
	}

	// 更新订单服务费金额快照
	s.tradeRepo.UpdateStatus(ctx, tradeNo, model.TradeStatusPaid, model.TradeStatusPaid,
		map[string]any{"service_fee_amount": feeAmount})

	// 创建服务费流水
	log := &model.ServiceFeeLog{
		TradeNo:            tradeNo,
		ConfigID:           cfg.ID,
		FeeAmount:          feeAmount,
		FeeRate:            cfg.FeeRate,
		ReceiverMerchantID: cfg.FeeReceiverMerchantID,
		Action:             "CHARGE",
		Status:             "PENDING",
	}
	if err := s.feeRepo.CreateLog(ctx, log); err != nil {
		return err
	}

	// 调用渠道分账
	ch, err := s.channelSvc.GetChannel(ctx, order.AppID, order.ChannelCode)
	if err != nil {
		s.feeRepo.UpdateLogStatus(ctx, log.ID, "FAILED", "")
		return err
	}

	resp, err := ch.ProfitSharing(ctx, &channel.ProfitSharingReq{
		TradeNo:            tradeNo,
		ChannelTradeNo:     order.ChannelTradeNo,
		SharingNo:          fmt.Sprintf("FEE%s", tradeNo),
		ReceiverMerchantID: cfg.FeeReceiverMerchantID,
		Amount:             feeAmount,
	})
	if err != nil {
		s.feeRepo.UpdateLogStatus(ctx, log.ID, "FAILED", "")
		slog.WarnContext(ctx, "charge service fee failed", "trade_no", tradeNo, "err", err)
		return err
	}

	s.feeRepo.UpdateLogStatus(ctx, log.ID, "SUCCESS", resp.ChannelSharingNo)
	slog.InfoContext(ctx, "service fee charged", "trade_no", tradeNo, "fee_amount", feeAmount)
	return nil
}

// RollbackServiceFee 退款时回退服务费
func (s *ServiceFeeService) RollbackServiceFee(ctx context.Context, tradeNo string) error {
	// 幂等检查
	existing, err := s.feeRepo.GetLog(ctx, tradeNo, "ROLLBACK")
	if err != nil {
		return err
	}
	if existing != nil {
		return nil // 已回退
	}

	chargeLog, err := s.feeRepo.GetLog(ctx, tradeNo, "CHARGE")
	if err != nil {
		return err
	}
	if chargeLog == nil || chargeLog.Status != "SUCCESS" {
		return nil // 没有成功扣收，无需回退
	}

	order, err := s.tradeRepo.GetByTradeNo(ctx, tradeNo)
	if err != nil || order == nil {
		return fmt.Errorf("order not found: %s", tradeNo)
	}

	rollbackLog := &model.ServiceFeeLog{
		TradeNo:            tradeNo,
		ConfigID:           chargeLog.ConfigID,
		FeeAmount:          chargeLog.FeeAmount,
		FeeRate:            chargeLog.FeeRate,
		ReceiverMerchantID: chargeLog.ReceiverMerchantID,
		Action:             "ROLLBACK",
		Status:             "PENDING",
	}
	if err := s.feeRepo.CreateLog(ctx, rollbackLog); err != nil {
		return err
	}

	ch, err := s.channelSvc.GetChannel(ctx, order.AppID, order.ChannelCode)
	if err != nil {
		return err
	}

	sharingNo := fmt.Sprintf("FEE%s", tradeNo)
	if err := ch.RollbackProfitSharing(ctx, &channel.RollbackSharingReq{
		SharingNo:        sharingNo,
		ChannelSharingNo: chargeLog.ChannelSharingNo,
		TradeNo:          tradeNo,
	}); err != nil {
		s.feeRepo.UpdateLogStatus(ctx, rollbackLog.ID, "FAILED", "")
		return err
	}

	s.feeRepo.UpdateLogStatus(ctx, rollbackLog.ID, "SUCCESS", "")
	return nil
}

// CalculateAndValidate 下单时校验分润+服务费不超过订单金额
func (s *ServiceFeeService) CalculateAndValidate(ctx context.Context, appID string, payMethod model.PayMethod, orderAmount, sharingAmount int64) (int64, error) {
	group := model.PayMethodToGroup(payMethod)
	cfg, err := s.feeRepo.GetConfig(ctx, appID, group)
	if err != nil {
		return 0, err
	}

	var feeAmount int64
	if cfg != nil && cfg.FeeRate > 0 {
		feeAmount = calculateFee(orderAmount, cfg.FeeRate)
	}

	if sharingAmount+feeAmount > orderAmount {
		return 0, fmt.Errorf(errSharingFeeExceed)
	}
	return feeAmount, nil
}

const errSharingFeeExceed = "30007" // errcode.ErrSharingFeeExceed

// calculateFee 计算服务费（四舍五入到分）
func calculateFee(amount int64, rate float64) int64 {
	fee := float64(amount) * rate
	return int64(math.Round(fee))
}