AI edits: add a calculator feature

py-server/api/controllers/calculatorController.py

@@ -0,0 +1,76 @@
+from fastapi import APIRouter, HTTPException
+from pydantic import BaseModel
+import ast
+import operator
+
+# Data model for the request body
+class ExpressionRequest(BaseModel):
+    expression: str
+
+# Mapping of allowed binary operators
+_BINARY_OPERATORS = {
+    ast.Add: operator.add,
+    ast.Sub: operator.sub,
+    ast.Mult: operator.mul,
+    ast.Div: operator.truediv,
+    ast.Pow: operator.pow,
+    ast.Mod: operator.mod,
+}
+
+# Mapping of allowed unary operators
+_UNARY_OPERATORS = {
+    ast.UAdd: operator.pos,
+    ast.USub: operator.neg,
+}
+
+def _eval_node(node: ast.AST) -> float:
+    """Recursively evaluate an AST node safely."""
+    if isinstance(node, ast.Constant):  # Python 3.8+
+        if isinstance(node.value, (int, float)):
+            return node.value
+        raise ValueError("Only numeric constants are allowed.")
+    if isinstance(node, ast.Num):  # Python <3.8
+        return node.n
+    if isinstance(node, ast.BinOp):
+        left = _eval_node(node.left)
+        right = _eval_node(node.right)
+        op_func = _BINARY_OPERATORS.get(type(node.op))
+        if op_func is None:
+            raise ValueError(f"Unsupported binary operator: {type(node.op).__name__}")
+        return op_func(left, right)
+    if isinstance(node, ast.UnaryOp):
+        operand = _eval_node(node.operand)
+        op_func = _UNARY_OPERATORS.get(type(node.op))
+        if op_func is None:
+            raise ValueError(f"Unsupported unary operator: {type(node.op).__name__}")
+        return op_func(operand)
+    raise ValueError(f"Unsupported expression type: {type(node).__name__}")
+
+def safe_eval(expression: str) -> float:
+    """
+    Safely evaluate a mathematical expression containing only numbers
+    and the operators +, -, *, /, **, and %.
+    """
+    try:
+        parsed = ast.parse(expression, mode="eval")
+    except SyntaxError as exc:
+        raise ValueError("Invalid syntax") from exc
+
+    return _eval_node(parsed.body)
+
+router = APIRouter()
+
+@router.post("/calculator")
+async def calculate(request: ExpressionRequest):
+    """
+    Evaluate a mathematical expression sent in the request body.
+    The request body must contain a JSON object with an 'expression' field.
+    """
+    try:
+        result = safe_eval(request.expression)
+    except Exception as exc:
+        raise HTTPException(status_code=400, detail=str(exc))
+
+    return {"result": result}
+
+__all__ = ["router"]