test: harden business boundary conditions

apps/server/src/wallets/wallets.service.spec.ts

@@ -50,3 +50,70 @@ describe('WalletsService payment rules', () => {
     expect(ctx.saved.some((row) => row.type === 'bill_refund' && Number(row.amount) === 40)).toBe(true);
   });
 });
+
+describe('WalletsService financial boundaries', () => {
+  it('caps a debit at total minus already paid even when outstandingAmount is stale', async () => {
+    const ctx = manager(50);
+    const service = new WalletsService({} as any, {} as any, {} as any, {} as any);
+    const bill = {
+      id: 10,
+      studentId: 10,
+      totalAmount: 100,
+      paidAmount: 90,
+      outstandingAmount: 100,
+      status: 'partially_paid',
+    } as Bill;
+
+    await service.debitBill(ctx.value as any, bill);
+
+    expect(bill).toMatchObject({ paidAmount: 100, outstandingAmount: 0, status: 'paid' });
+    expect(ctx.wallet.balance).toBe(40);
+    expect(ctx.saved.some((row) => row.type === 'bill_payment' && row.amount === -10)).toBe(true);
+  });
+
+  it('caps a refund at the bill total when paidAmount is corrupt', async () => {
+    const ctx = manager(10);
+    const service = new WalletsService({} as any, {} as any, {} as any, {} as any);
+    const bill = {
+      id: 11,
+      studentId: 10,
+      totalAmount: 100,
+      paidAmount: 150,
+      outstandingAmount: 0,
+      status: 'paid',
+    } as Bill;
+
+    await service.refundBill(ctx.value as any, bill, '冲正');
+
+    expect(ctx.wallet.balance).toBe(110);
+    expect(ctx.saved.some((row) => row.type === 'bill_refund' && row.amount === 100)).toBe(true);
+  });
+
+  it('does not issue a second refund for an already cancelled bill', async () => {
+    const ctx = manager(10);
+    const service = new WalletsService({} as any, {} as any, {} as any, {} as any);
+    const bill = {
+      id: 12,
+      studentId: 10,
+      totalAmount: 100,
+      paidAmount: 100,
+      outstandingAmount: 0,
+      status: 'cancelled',
+    } as Bill;
+
+    await service.refundBill(ctx.value as any, bill, '重复取消');
+
+    expect(ctx.wallet.balance).toBe(10);
+    expect(ctx.saved).toHaveLength(0);
+  });
+
+  it('rejects an amount that rounds to zero before opening a transaction', async () => {
+    const dataSource = { transaction: jest.fn() };
+    const service = new WalletsService({} as any, {} as any, {} as any, dataSource as any);
+
+    await expect(service.changeBalance({ studentId: 1, amount: 0.004, type: 'adjustment' })).rejects.toBeInstanceOf(
+      BadRequestException,
+    );
+    expect(dataSource.transaction).not.toHaveBeenCalled();
+  });
+});

apps/server/src/wallets/wallets.service.ts

@@ -61,12 +61,17 @@ export class WalletsService {
   }
 
   async changeBalance(dto: ChangeWalletBalanceDto, recordedBy?: number) {
-    if (dto.type === 'recharge' && dto.amount <= 0) throw new BadRequestException('充值金额必须大于 0');
+    const amount = money(dto.amount);
+    if (!Number.isFinite(dto.amount) || Math.abs(dto.amount * 100 - Math.round(dto.amount * 100)) > 1e-8) {
+      throw new BadRequestException('调账金额最多保留两位小数');
+    }
+    if (amount === 0) throw new BadRequestException('调账金额不能为 0');
+    if (dto.type === 'recharge' && amount <= 0) throw new BadRequestException('充值金额必须大于 0');
     const student = await this.studentRepo.findOne({ where: { id: dto.studentId } });
     if (!student) throw new NotFoundException('学生不存在');
     return this.dataSource.transaction(async (manager) => {
       const wallet = await this.getOrCreateWallet(manager, dto.studentId);
-      const nextBalance = money(Number(wallet.balance) + dto.amount);
+      const nextBalance = money(Number(wallet.balance) + amount);
       if (nextBalance < 0) throw new BadRequestException('调账后余额不能小于 0');
       wallet.balance = nextBalance;
       await manager.save(wallet);
@@ -75,29 +80,43 @@ export class WalletsService {
           studentId: dto.studentId,
           billId: null,
           type: dto.type,
-          amount: money(dto.amount),
+          amount,
           balanceAfter: nextBalance,
           description: dto.description || (dto.type === 'recharge' ? '财务充值' : '余额调账'),
           recordedBy: recordedBy || null,
         }),
       );
-      const payments = dto.amount > 0 ? await this.settleOutstandingBills(manager, dto.studentId, recordedBy) : [];
+      const payments = amount > 0 ? await this.settleOutstandingBills(manager, dto.studentId, recordedBy) : [];
       const finalWallet = await manager.findOneByOrFail(StudentWallet, { studentId: dto.studentId });
       return { wallet: finalWallet, payments };
     });
   }
 
   async debitBill(manager: EntityManager, bill: Bill, recordedBy?: number) {
-    if (bill.status === 'cancelled' || money(bill.outstandingAmount) <= 0) return bill;
-    const wallet = await this.getOrCreateWallet(manager, bill.studentId);
-    const amount = money(Math.min(Number(wallet.balance), Number(bill.outstandingAmount)));
-    if (amount <= 0) {
-      bill.status = money(bill.paidAmount) > 0 ? 'partially_paid' : 'unpaid';
+    if (bill.status === 'cancelled') return bill;
+
+    const total = money(bill.totalAmount);
+    const paid = Math.max(0, Math.min(money(bill.paidAmount), total));
+    const remaining = money(Math.max(0, total - paid));
+    if (remaining <= 0) {
+      bill.paidAmount = total;
+      bill.outstandingAmount = 0;
+      bill.status = 'paid';
       return manager.save(bill);
     }
+
+    const wallet = await this.getOrCreateWallet(manager, bill.studentId);
+    const amount = money(Math.min(Math.max(0, money(wallet.balance)), remaining));
+    if (amount <= 0) {
+      bill.paidAmount = paid;
+      bill.outstandingAmount = remaining;
+      bill.status = paid > 0 ? 'partially_paid' : 'unpaid';
+      return manager.save(bill);
+    }
+
     wallet.balance = money(Number(wallet.balance) - amount);
-    bill.paidAmount = money(Number(bill.paidAmount) + amount);
-    bill.outstandingAmount = money(Number(bill.totalAmount) - Number(bill.paidAmount));
+    bill.paidAmount = money(paid + amount);
+    bill.outstandingAmount = money(Math.max(0, total - Number(bill.paidAmount)));
     bill.status = bill.outstandingAmount <= 0 ? 'paid' : 'partially_paid';
     await manager.save(wallet);
     await manager.save(bill);
@@ -109,14 +128,16 @@ export class WalletsService {
         amount: -amount,
         balanceAfter: wallet.balance,
         description: `账单 #${bill.id} 自动扣款`,
-        recordedBy: recordedBy || null,
+        recordedBy: recordedBy ?? null,
       }),
     );
     return bill;
   }
 
   async refundBill(manager: EntityManager, bill: Bill, reason: string, recordedBy?: number) {
-    const paid = money(bill.paidAmount);
+    if (bill.status === 'cancelled') return bill;
+
+    const paid = Math.max(0, Math.min(money(bill.paidAmount), money(bill.totalAmount)));
     if (paid > 0) {
       const wallet = await this.getOrCreateWallet(manager, bill.studentId);
       wallet.balance = money(Number(wallet.balance) + paid);
@@ -129,7 +150,7 @@ export class WalletsService {
           amount: paid,
           balanceAfter: wallet.balance,
           description: `取消账单 #${bill.id} 冲正：${reason}`,
-          recordedBy: recordedBy || null,
+          recordedBy: recordedBy ?? null,
         }),
       );
     }