from typing import Dict, Any
from langchain_core.tools import BaseTool


class CalculatorTool(BaseTool):
    """用于数学运算的简单计算器工具"""
    
    name: str = "calculator"
    description: str = "Perform mathematical calculations. Input should be a mathematical expression like '2 + 2' or '10 * (3 + 5)'"
    
    def _run(self, expression: str) -> str:
        """计算数学表达式"""
        try:
            # 安全：仅允许安全的数学运算
            allowed_chars = set("0123456789+-*/(). ")
            if not all(c in allowed_chars for c in expression):
                return "Error: Expression contains invalid characters"
            
            # 计算表达式
            result = eval(expression)
            return f"Result: {result}"
        except Exception as e:
            return f"Error calculating expression: {str(e)}"
    
    async def _arun(self, expression: str) -> str:
        """工具的异步版本"""
        return self._run(expression)