import ast
from typing import Any, Dict


def safe_calculator(expr: str) -> float:
    """
    Parse arithmetic expressions using ast and support + - * / ** and parentheses.
    """
    allowed_nodes = {
        ast.Expression,
        ast.BinOp,
        ast.UnaryOp,
        ast.Add,
        ast.Sub,
        ast.Mult,
        ast.Div,
        ast.Pow,
        ast.USub,
        ast.UAdd,
        ast.Constant,
        ast.Load,
        ast.Mod,
    }

    node = ast.parse(expr, mode="eval")
    if not all(isinstance(n, tuple(allowed_nodes)) for n in ast.walk(node)):
        raise ValueError("Unsupported expression")
    return eval(compile(node, "<safe_calculator>", mode="eval"))


def get_calculator_tools() -> list[Dict[str, Any]]:
    """Get calculator tool definitions for LLM function calling."""
    return [
        {
            "type": "function",
            "function": {
                "name": "safe_calculator",
                "description": "Perform simple arithmetic calculations",
                "parameters": {
                    "type": "object",
                    "properties": {
                        "expression": {
                            "type": "string",
                            "description": "Arithmetic expression to evaluate (supports +, -, *, /, **, %, and parentheses). Example: 2000 + 5000",
                        }
                    },
                    "required": ["expression"],
                },
            },
        }
    ]