feat: link deposits to bill payment

apps/server/src/bills/bills.service.ts

@@ -1,6 +1,6 @@
-import { Injectable, NotFoundException } from '@nestjs/common';
+import { BadRequestException, Injectable, NotFoundException } from '@nestjs/common';
 import { InjectRepository } from '@nestjs/typeorm';
-import { Repository, In, DataSource } from 'typeorm';
+import { Repository, In, DataSource, EntityManager } from 'typeorm';
 import { Bill } from '../entities/bill.entity';
 import { BillItem } from '../entities/bill-item.entity';
 import { RoomExpense } from '../entities/room-expense.entity';
@@ -28,26 +28,15 @@ export class BillsService {
    * 核心计费引擎：按"人天数"加权分摊
    */
   async generateBills(dto: GenerateBillsDto) {
-    const { periodStart, periodEnd } = dto;
+    const { periodStart, periodEnd } = this.resolveBillingPeriod(dto.billingMonth);
     const pStart = new Date(periodStart);
     const pEnd = new Date(periodEnd);
 
-    // 删除该周期已有的草稿账单
-    const existingDrafts = await this.billRepo.find({
-      where: { periodStart, periodEnd, status: 'draft' },
+    const existingBills = await this.billRepo.find({
+      where: { periodStart, periodEnd },
     });
-    if (existingDrafts.length > 0) {
-      const draftIds = existingDrafts.map((b) => b.id);
-      await this.itemRepo
-        .createQueryBuilder()
-        .delete()
-        .where('billId IN (:...ids)', { ids: draftIds })
-        .execute();
-      await this.billRepo
-        .createQueryBuilder()
-        .delete()
-        .where('id IN (:...ids)', { ids: draftIds })
-        .execute();
+    if (existingBills.length > 0) {
+      throw new BadRequestException(`${dto.billingMonth} 月账单已生成，不能重复生成`);
     }
 
     // 获取账单周期内所有有费用的宿舍
@@ -208,7 +197,41 @@ export class BillsService {
       bills.push(savedBill);
     }
 
-    return { message: `成功生成 ${bills.length} 条账单`, count: bills.length, bills };
+    return {
+      message: `成功生成 ${dto.billingMonth} 月 ${bills.length} 条账单`,
+      count: bills.length,
+      periodStart,
+      periodEnd,
+      bills,
+    };
+  }
+
+  private resolveBillingPeriod(billingMonth: string) {
+    const matched = /^(\d{4})-(\d{2})$/.exec(billingMonth || '');
+    if (!matched) {
+      throw new BadRequestException('账单月份格式错误，请使用 YYYY-MM');
+    }
+
+    const year = Number(matched[1]);
+    const month = Number(matched[2]);
+    if (month < 1 || month > 12) {
+      throw new BadRequestException('账单月份格式错误，请使用 YYYY-MM');
+    }
+
+    const targetMonthStart = new Date(year, month - 1, 1);
+    const currentMonthStart = new Date();
+    currentMonthStart.setDate(1);
+    currentMonthStart.setHours(0, 0, 0, 0);
+    if (targetMonthStart >= currentMonthStart) {
+      throw new BadRequestException('只能生成已结束月份的账单');
+    }
+
+    const targetMonthEnd = new Date(year, month, 0);
+    const pad = (value: number) => String(value).padStart(2, '0');
+    return {
+      periodStart: `${year}-${pad(month)}-01`,
+      periodEnd: `${year}-${pad(month)}-${pad(targetMonthEnd.getDate())}`,
+    };
   }
 
   async findAll(query?: {
@@ -242,9 +265,9 @@ export class BillsService {
 
   /**
    * 给账单挂上"押金联动"信息：
-   * - availableDeposit: 当前学生处于已缴未退状态(paid)的押金总额
-   * - depositApplied:   本张账单可从押金抵扣的金额（min(押金, 应付总额)）
-   * - amountAfterDeposit: 抵扣押金后学生需另外支付的金额
+   * - availableDeposit: 学生当前实时可用押金余额，生成账单时不会冻结
+   * - depositSufficient: 草稿账单是否已有足够余额可确认
+   * - depositDeductedAmount: 已确认账单实际扣除的押金金额
    */
   private async attachDepositInfo(bills: Bill[]): Promise<any[]> {
     if (!bills || bills.length === 0) return bills;
@@ -253,7 +276,6 @@ export class BillsService {
     const deposits = await this.depositRepo
       .createQueryBuilder('d')
       .where('d.studentId IN (:...ids)', { ids: studentIds })
-      .andWhere('d.status = :status', { status: 'paid' })
       .getMany();
     const depMap = new Map<number, number>();
     for (const d of deposits) {
@@ -262,42 +284,83 @@ export class BillsService {
     return bills.map((b) => {
       const total = Number(b.totalAmount || 0);
       const available = Number((depMap.get(b.studentId) || 0).toFixed(2));
-      const applied = Number(Math.min(available, total).toFixed(2));
-      const afterDeposit = Number(Math.max(0, total - applied).toFixed(2));
       return Object.assign({}, b, {
         availableDeposit: available,
-        depositApplied: applied,
-        amountAfterDeposit: afterDeposit,
+        depositSufficient: available >= total,
+        depositDeductedAmount: Number(b.depositDeductedAmount || 0),
       });
     });
   }
 
   async updateStatus(id: number, dto: UpdateBillStatusDto) {
-    const bill = await this.billRepo.findOne({ where: { id } });
-    if (!bill) throw new NotFoundException('账单不存在');
-    bill.status = dto.status;
-    return this.billRepo.save(bill);
+    if (dto.status !== 'paid') {
+      throw new BadRequestException('账单只能通过确认支付完成扣款');
+    }
+    return this.dataSource.transaction((manager) => this.payBill(manager, id));
   }
 
   async batchUpdateStatus(ids: number[], status: string) {
-    await this.billRepo
-      .createQueryBuilder()
-      .update()
-      .set({ status })
-      .where('id IN (:...ids)', { ids })
-      .execute();
-    return { message: `成功更新 ${ids.length} 条账单状态` };
+    if (status !== 'paid') {
+      throw new BadRequestException('账单只能通过确认支付完成扣款');
+    }
+    const uniqueIds = Array.from(new Set(ids));
+    await this.dataSource.transaction(async (manager) => {
+      for (const id of uniqueIds) await this.payBill(manager, id);
+    });
+    return { message: `成功确认 ${uniqueIds.length} 条账单并扣除押金` };
+  }
+
+  private async payBill(manager: EntityManager, id: number) {
+    const billRepo = manager.getRepository(Bill);
+    const depositRepo = manager.getRepository(Deposit);
+    const lock = this.supportsPessimisticLocks()
+      ? ({ mode: 'pessimistic_write' } as const)
+      : undefined;
+    const bill = await billRepo.findOne({ where: { id }, ...(lock ? { lock } : {}) });
+    if (!bill) throw new NotFoundException(`账单 ${id} 不存在`);
+    if (bill.status === 'paid') return bill;
+    if (bill.status !== 'draft') throw new BadRequestException(`账单 ${id} 当前状态无法确认支付`);
+
+    const deposit = await depositRepo.findOne({
+      where: { studentId: bill.studentId },
+      ...(lock ? { lock } : {}),
+    });
+    const available = Number(deposit?.amount || 0);
+    const required = Number(bill.totalAmount || 0);
+    if (!deposit || available < required) {
+      throw new BadRequestException(
+        `账单 ${id} 押金不足：需 ¥${required.toFixed(2)}，当前可用 ¥${available.toFixed(2)}，请先到押金管理收取押金`,
+      );
+    }
+
+    deposit.amount = Number((available - required).toFixed(2));
+    deposit.status = deposit.amount > 0 ? 'paid' : 'depleted';
+    bill.depositDeductedAmount = required;
+    bill.status = 'paid';
+    await depositRepo.save(deposit);
+    return billRepo.save(bill);
+  }
+
+  private supportsPessimisticLocks() {
+    return ['mysql', 'mariadb', 'postgres', 'cockroachdb', 'mssql', 'oracle'].includes(
+      String(this.dataSource.options.type),
+    );
   }
 
   async remove(id: number) {
     const exists = await this.billRepo.findOne({ where: { id } });
     if (!exists) throw new NotFoundException('账单不存在');
+    if (exists.status === 'paid') throw new BadRequestException('已支付账单不能删除');
     await this.itemRepo.delete({ billId: id });
     await this.billRepo.delete(id);
     return { message: '账单已删除' };
   }
 
   async batchRemove(ids: number[]) {
+    const bills = await this.billRepo.find({ where: { id: In(ids) } });
+    if (bills.some((bill) => bill.status === 'paid')) {
+      throw new BadRequestException('已支付账单不能删除');
+    }
     await this.itemRepo
       .createQueryBuilder()
       .delete()