jsowell-charger-web/TestCalculateBalanceRefund.java

import java.math.BigDecimal;
import java.util.HashMap;
import java.util.Map;

public class TestCalculateBalanceRefund {

    /**
     * 计算余额退款（包含电费和保险费）
     * <p>
     * 业务规则：
     * 1. 总支付金额 = principalPay + giftPay
     * 2. 电费预付款 = 总支付金额 - insuranceAmount
     * 3. 实际电费消费金额 = orderAmount - discountAmount
     * 4. 支付时优先使用本金，消费时也优先扣除本金
     * 5. 保险费优先从本金中扣除
     * 6. 电费实际消费金额 > 1 时，保险费不退；否则需要退保险费
     *
     * @param principalPay    本金支付金额
     * @param giftPay         赠金支付金额
     * @param orderAmount     消费金额
     * @param discountAmount  折扣金额
     * @param insuranceAmount 保险费金额
     * @return Map包含：returnPrincipal（本金退款for电费），returnGift（赠金退款for电费），
     *         returnPrincipalForInsurance（本金退款for保险费），returnGiftForInsurance（赠金退款for保险费）
     */
    protected static Map<String, BigDecimal> calculateBalanceRefund(BigDecimal principalPay, BigDecimal giftPay,
                                                                    BigDecimal orderAmount, BigDecimal discountAmount,
                                                                    BigDecimal insuranceAmount) {
        Map<String, BigDecimal> resultMap = new HashMap<>();

        // 参数校验，null值处理为0
        principalPay = principalPay == null ? BigDecimal.ZERO : principalPay;
        giftPay = giftPay == null ? BigDecimal.ZERO : giftPay;
        orderAmount = orderAmount == null ? BigDecimal.ZERO : orderAmount;
        discountAmount = discountAmount == null ? BigDecimal.ZERO : discountAmount;
        insuranceAmount = insuranceAmount == null ? BigDecimal.ZERO : insuranceAmount;

        // 总支付金额
        BigDecimal totalPay = principalPay.add(giftPay);

        // 电费预付款 = 总支付金额 - 保险费
        BigDecimal electricityPrepayment = totalPay.subtract(insuranceAmount);

        // 实际电费消费金额 = 消费金额 - 折扣金额
        BigDecimal actualElectricityConsumption = orderAmount.subtract(discountAmount);
        if (actualElectricityConsumption.compareTo(BigDecimal.ZERO) < 0) {
            actualElectricityConsumption = BigDecimal.ZERO;
        }

        // 支付时优先用本金，保险费全部从本金中扣除
        // 本金用于保险费的部分（优先从本金扣除保险费）
        BigDecimal principalForInsurance = principalPay.min(insuranceAmount);
        // 赠金用于保险费的部分（如果本金不够支付保险费，从赠金中扣除）
        BigDecimal giftForInsurance = insuranceAmount.subtract(principalForInsurance);
        if (giftForInsurance.compareTo(BigDecimal.ZERO) < 0) {
            giftForInsurance = BigDecimal.ZERO;
        }
        // 本金用于电费的部分 = 总本金 - 本金用于保险费的部分
        BigDecimal principalForElectricity = principalPay.subtract(principalForInsurance);
        // 赠金用于电费的部分 = 总赠金 - 赠金用于保险费的部分
        BigDecimal giftForElectricity = giftPay.subtract(giftForInsurance);

        // 计算电费退款（消费时优先扣除本金）
        BigDecimal principalConsumed = principalForElectricity.min(actualElectricityConsumption);
        BigDecimal giftConsumed = actualElectricityConsumption.subtract(principalConsumed);
        if (giftConsumed.compareTo(BigDecimal.ZERO) < 0) {
            giftConsumed = BigDecimal.ZERO;
        }

        // 电费退款
        BigDecimal returnPrincipal = principalForElectricity.subtract(principalConsumed);
        BigDecimal returnGift = giftForElectricity.subtract(giftConsumed);
        if (returnPrincipal.compareTo(BigDecimal.ZERO) < 0) {
            returnPrincipal = BigDecimal.ZERO;
        }
        if (returnGift.compareTo(BigDecimal.ZERO) < 0) {
            returnGift = BigDecimal.ZERO;
        }

        // 计算保险费退款：电费实际消费金额 > 1 时，保险费不退；否则需要退保险费
        BigDecimal returnPrincipalForInsurance = BigDecimal.ZERO;
        BigDecimal returnGiftForInsurance = BigDecimal.ZERO;

        if (actualElectricityConsumption.compareTo(BigDecimal.ONE) <= 0) {
            // 需要退保险费
            returnPrincipalForInsurance = principalForInsurance;
            returnGiftForInsurance = giftForInsurance;
        }

        resultMap.put("returnPrincipal", returnPrincipal);
        resultMap.put("returnGift", returnGift);
        resultMap.put("returnPrincipalForInsurance", returnPrincipalForInsurance);
        resultMap.put("returnGiftForInsurance", returnGiftForInsurance);

        System.out.println("计算余额退款: 本金支付=" + principalPay + ", 赠金支付=" + giftPay +
                         ", 消费金额=" + orderAmount + ", 折扣金额=" + discountAmount +
                         ", 保险费=" + insuranceAmount + ", 实际电费消费=" + actualElectricityConsumption +
                         ", 电费退款(本金=" + returnPrincipal + ", 赠金=" + returnGift +
                         "), 保险费退款(本金=" + returnPrincipalForInsurance + ", 赠金=" + returnGiftForInsurance + ")");

        return resultMap;
    }

    public static void main(String[] args) {
        System.out.println("测试用例1: 本金30.5, 赠金20, 消费10, 折扣0, 保险费0.5");
        BigDecimal principalPay = new BigDecimal("30.5");
        BigDecimal giftPay = new BigDecimal("20");
        BigDecimal orderAmount = new BigDecimal("10");
        BigDecimal discountAmount = new BigDecimal("0");
        BigDecimal insuranceAmount = new BigDecimal("0.5");

        Map<String, BigDecimal> result = calculateBalanceRefund(principalPay, giftPay, orderAmount, discountAmount, insuranceAmount);
        System.out.println("结果: " + result);
        System.out.println();

        System.out.println("期望结果: 电费退款(本金=20.5, 赠金=19.5), 保险费退款(本金=0, 赠金=0)");
        System.out.println("实际结果: 电费退款(本金=" + result.get("returnPrincipal") +
                         ", 赠金=" + result.get("returnGift") +
                         "), 保险费退款(本金=" + result.get("returnPrincipalForInsurance") +
                         ", 赠金=" + result.get("returnGiftForInsurance") + ")");
    }
}