feat: add math engine and puzzle services

backend/toolbox/views.py

@@ -0,0 +1,22 @@
+from rest_framework import permissions
+from rest_framework.exceptions import ValidationError
+from rest_framework.response import Response
+from rest_framework.throttling import ScopedRateThrottle
+from rest_framework.views import APIView
+
+from .engine import calculate
+
+
+class CalculatorView(APIView):
+    permission_classes = [permissions.AllowAny]
+    throttle_classes = [ScopedRateThrottle]
+    throttle_scope = "calculator"
+
+    def post(self, request):
+        try:
+            payload = calculate(request.data)
+        except ValidationError:
+            raise
+        except (ArithmeticError, NotImplementedError, TypeError, ValueError) as exc:
+            raise ValidationError({"expression": "该计算暂时无法完成，请缩小表达式范围"}) from exc
+        return Response(payload)