@Service
public class UserService {
    // 整个容器中只有一个 UserService 实例
}

// Controller 层
@RestController
@RequestMapping("/api/credit")
public class CreditController {

    @Autowired
    private CreditService creditService;

    @PostMapping("/apply")
    public Result<CreditApplyResponse> apply(@RequestBody CreditApplyRequest request) {
        return Result.success(creditService.apply(request));
    }
}

// Service 层
@Service
public class CreditService {

    @Autowired
    private CustomerMapper customerMapper;

    @Autowired
    private CreditRecordMapper creditRecordMapper;

    @Autowired
    private RiskEngineClient riskEngineClient;

    @Transactional
    public CreditApplyResponse apply(CreditApplyRequest request) {
        // 1. 查询客户信息
        CustomerDO customer = customerMapper.selectById(request.getCustomerId());
        if (customer == null) {
            throw new BusinessException("客户不存在");
        }

        // 2. 校验客户状态
        if (!"ACTIVE".equals(customer.getStatus())) {
            throw new BusinessException("客户状态异常，无法申请授信");
        }

        // 3. 校验是否已有有效授信
        CreditRecordDO existingCredit = creditRecordMapper
            .selectByCustomerId(request.getCustomerId());
        if (existingCredit != null && "VALID".equals(existingCredit.getStatus())) {
            throw new BusinessException("已存在有效授信，无需重复申请");
        }

        // 4. 调用风控引擎
        RiskResult riskResult = riskEngineClient.evaluate(buildRiskRequest(customer));
        if (!riskResult.isPassed()) {
            CreditRecordDO failedRecord = new CreditRecordDO();
            failedRecord.setCustomerId(request.getCustomerId());
            failedRecord.setStatus("REJECTED");
            failedRecord.setRejectReason(riskResult.getReason());
            failedRecord.setCreateTime(new Date());
            creditRecordMapper.insert(failedRecord);
            return CreditApplyResponse.rejected(riskResult.getReason());
        }

        // 5. 计算授信额度
        BigDecimal creditAmount = calculateCreditAmount(customer, riskResult);

        // 6. 保存授信记录
        CreditRecordDO record = new CreditRecordDO();
        record.setCustomerId(request.getCustomerId());
        record.setCreditAmount(creditAmount);
        record.setStatus("VALID");
        record.setEffectiveDate(new Date());
        record.setExpireDate(calculateExpireDate());
        record.setCreateTime(new Date());
        creditRecordMapper.insert(record);

        return CreditApplyResponse.success(creditAmount);
    }

    private BigDecimal calculateCreditAmount(CustomerDO customer, RiskResult riskResult) {
        BigDecimal baseAmount = customer.getAnnualIncome()
            .multiply(new BigDecimal("0.5"));
        BigDecimal adjustedAmount = baseAmount
            .multiply(riskResult.getCreditMultiplier());
        return adjustedAmount.min(new BigDecimal("500000"));
    }
}

// 数据对象（贫血模型）
@Data
@TableName("t_customer")
public class CustomerDO {
    private Long id;
    private String name;
    private String idCard;
    private String phone;
    private String status;
    private BigDecimal annualIncome;
    private String companyName;
    private Date createTime;
    private Date updateTime;
}

@Data
@TableName("t_credit_record")
public class CreditRecordDO {
    private Long id;
    private Long customerId;
    private BigDecimal creditAmount;
    private String status;
    private String rejectReason;
    private Date effectiveDate;
    private Date expireDate;
    private Date createTime;
}