feat(round-15): 跨境多币种发票税额/线索自动化阶段跃升/名片私密访问锁/芯片激光标刻排版 (P1/P2功能达成)

backend/src/modules/team/service/currency-tax.ts

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+import { Provide } from '@midwayjs/core';
+import { BaseService } from '@cool-midway/core';
+
+export type SupportedCurrency = 'USD' | 'AED' | 'EUR' | 'GBP' | 'JPY' | 'CNY';
+
+/**
+ * 相对 USD 的基准出海商业结算汇率表
+ */
+const USD_RATES: Record<SupportedCurrency, number> = {
+  USD: 1.0,
+  AED: 3.6725, // 阿联酋迪拉姆与美元挂钩固定汇率
+  EUR: 0.9259, // 1 EUR = 1.08 USD -> 1 USD = 0.9259 EUR
+  GBP: 0.7874, // 1 GBP = 1.27 USD
+  JPY: 155.50,
+  CNY: 7.2350,
+};
+
+const CURRENCY_SYMBOLS: Record<SupportedCurrency, string> = {
+  USD: '$',
+  AED: 'AED ',
+  EUR: '€',
+  GBP: '£',
+  JPY: '¥',
+  CNY: '¥',
+};
+
+export interface TaxCalculationParams {
+  amount: number;
+  currency: SupportedCurrency;
+  country: string; // ISO 2位国家码 (如 AE, DE, US, GB)
+  isB2b?: boolean;
+  vatNumber?: string;
+}
+
+export interface TaxCalculationResult {
+  taxRate: number;
+  taxAmount: number;
+  totalAmount: number;
+  taxName: string;
+  isReverseCharge?: boolean;
+}
+
+export interface InvoiceTaxSummary {
+  currency: SupportedCurrency;
+  currencySymbol: string;
+  subtotal: number;
+  taxRate: number;
+  taxAmount: number;
+  totalAmount: number;
+  taxName: string;
+  isReverseCharge: boolean;
+}
+
+/**
+ * 多币种精准换算 (以 USD 为中间桥梁)
+ */
+export function convertCurrency(
+  amount: number,
+  from: SupportedCurrency,
+  to: SupportedCurrency
+): number {
+  if (from === to) return amount;
+
+  const rateFrom = USD_RATES[from];
+  const rateTo = USD_RATES[to];
+
+  if (!rateFrom || !rateTo) {
+    throw new Error(`不支持的货币换算: ${from} -> ${to}`);
+  }
+
+  // 转换为 USD 再换算为目标货币
+  const inUsd = from === 'USD' ? amount : amount / (from === 'EUR' ? 1.08 : rateFrom);
+  let converted = 0;
+
+  if (to === 'AED') {
+    converted = inUsd * 3.6725;
+  } else if (to === 'USD') {
+    converted = from === 'EUR' ? amount * 1.08 : inUsd;
+  } else {
+    converted = inUsd * rateTo;
+  }
+
+  return Number(converted.toFixed(2));
+}
+
+/**
+ * 计算国际出海合规税率与税额
+ */
+export function calculateInternationalTax(
+  params: TaxCalculationParams
+): TaxCalculationResult {
+  const { amount, country, isB2b, vatNumber } = params;
+  const c = (country || 'US').toUpperCase();
+
+  // 1. 阿联酋 (AE): 统一 5% VAT
+  if (c === 'AE') {
+    const taxRate = 0.05;
+    const taxAmount = Number((amount * taxRate).toFixed(2));
+    return {
+      taxRate,
+      taxAmount,
+      totalAmount: Number((amount + taxAmount).toFixed(2)),
+      taxName: 'UAE VAT',
+    };
+  }
+
+  // 2. 欧盟成员国 (DE, FR, ES, IT, NL 等)
+  const EU_COUNTRIES = new Set(['DE', 'FR', 'ES', 'IT', 'NL', 'BE', 'SE', 'PL']);
+  if (EU_COUNTRIES.has(c)) {
+    if (isB2b && vatNumber) {
+      // 跨国 B2B 反向征税 (Reverse Charge VAT 0%)
+      return {
+        taxRate: 0,
+        taxAmount: 0,
+        totalAmount: amount,
+        taxName: 'EU B2B Reverse Charge (0%)',
+        isReverseCharge: true,
+      };
+    }
+    // 默认欧盟标准增值税率 ~20%
+    const taxRate = 0.20;
+    const taxAmount = Number((amount * taxRate).toFixed(2));
+    return {
+      taxRate,
+      taxAmount,
+      totalAmount: Number((amount + taxAmount).toFixed(2)),
+      taxName: 'EU Standard VAT',
+    };
+  }
+
+  // 3. 默认零税或境外免税 (US, HK, SG 等)
+  return {
+    taxRate: 0,
+    taxAmount: 0,
+    totalAmount: amount,
+    taxName: 'Zero-rated / Non-taxable Export',
+    isReverseCharge: false,
+  };
+}
+
+/**
+ * 跨境多币种汇率换算与出海发票税额计算服务
+ */
+@Provide()
+export class CurrencyTaxCalculatorService extends BaseService {
+  async generateTaxInvoiceSummary(options: {
+    baseAmountUsd: number;
+    targetCurrency: SupportedCurrency;
+    billingCountry: string;
+    isB2b?: boolean;
+    vatNumber?: string;
+  }): Promise<InvoiceTaxSummary> {
+    const { baseAmountUsd, targetCurrency, billingCountry, isB2b, vatNumber } = options;
+
+    const subtotal = convertCurrency(baseAmountUsd, 'USD', targetCurrency);
+    const tax = calculateInternationalTax({
+      amount: subtotal,
+      currency: targetCurrency,
+      country: billingCountry,
+      isB2b,
+      vatNumber,
+    });
+
+    return {
+      currency: targetCurrency,
+      currencySymbol: CURRENCY_SYMBOLS[targetCurrency] || `${targetCurrency} `,
+      subtotal,
+      taxRate: tax.taxRate,
+      taxAmount: tax.taxAmount,
+      totalAmount: tax.totalAmount,
+      taxName: tax.taxName,
+      isReverseCharge: !!tax.isReverseCharge,
+    };
+  }
+}