feat: balance api

api_v1/views/business/balance/__init__.py

@@ -0,0 +1,4 @@
+"""
+余额相关 API 视图。
+"""
+

api_v1/views/business/balance/views.py

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+from decimal import Decimal
+
+from rest_framework import views
+from rest_framework.permissions import IsAuthenticated
+from rest_framework.response import Response
+
+from basic_info import models as basic_models
+from business import services as business_services
+from api_v1.views.stock_change_views.mixins import StockChangeViewMixin
+
+
+class CustomerBalanceView(StockChangeViewMixin, views.APIView):
+    permission_classes = [IsAuthenticated]
+
+    def get(self, request, customer_id: int):
+        if not self.check_employee_permission(request):
+            return self.permission_error_response('无权限访问')
+
+        merchant = request.user.employee.merchant
+        try:
+            customer = basic_models.Customer.objects.get(id=customer_id, merchant=merchant)
+        except basic_models.Customer.DoesNotExist:
+            return self.not_found_response('客户不存在')
+
+        balance: Decimal = business_services.BalanceService.get_customer_balance(
+            merchant=merchant,
+            customer=customer,
+        )
+        return Response(
+            {
+                'customer': customer.id,
+                'customer_name': customer.name,
+                'balance': str(balance),
+            }
+        )
+