# tools/calculator.py
import ast, operator as op
from smolagents import tool

_ops = {
    ast.Add: op.add, ast.Sub: op.sub, ast.Mult: op.mul,
    ast.Div: op.truediv, ast.Pow: op.pow, ast.Mod: op.mod,
    ast.USub: op.neg
}

def _safe_eval(node):
    if isinstance(node, ast.Expression):
        return _safe_eval(node.body)
    if isinstance(node, ast.Constant):
        return node.value
    if isinstance(node, ast.BinOp):
        return _ops[type(node.op)](_safe_eval(node.left), _safe_eval(node.right))
    if isinstance(node, ast.UnaryOp):
        return _ops[type(node.op)](_safe_eval(node.operand))
    raise ValueError("Unsupported expression")

@tool
def calculator(expression: str) -> str:
    """Evaluate a simple arithmetic expression safely.
    Args:
        expression: The math expression to evaluate.
    """
    tree = ast.parse(expression, mode="eval")
    return str(_safe_eval(tree))