first implementation

backend/routes/sum.py

@@ -0,0 +1,31 @@
+"""Sum calculation routes."""
+from fastapi import APIRouter, Depends
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from auth import require_permission
+from database import get_db
+from models import User, SumRecord, Permission
+from schemas import SumRequest, SumResponse
+
+
+router = APIRouter(prefix="/api/sum", tags=["sum"])
+
+
+@router.post("", response_model=SumResponse)
+async def calculate_sum(
+    data: SumRequest,
+    db: AsyncSession = Depends(get_db),
+    current_user: User = Depends(require_permission(Permission.USE_SUM)),
+) -> SumResponse:
+    """Calculate the sum of two numbers and record it."""
+    result = data.a + data.b
+    record = SumRecord(
+        user_id=current_user.id,
+        a=data.a,
+        b=data.b,
+        result=result,
+    )
+    db.add(record)
+    await db.commit()
+    return SumResponse(a=data.a, b=data.b, result=result)
+