import logging
from langchain_core.tools import StructuredTool
from pydantic import BaseModel, Field

logger = logging.getLogger(__name__)

class CalculatorInput(BaseModel):
    expression: str = Field(description="Mathematical expression to evaluate")

async def calculator_func(expression: str) -> str:
    """
    Evaluate a mathematical expression and return the result as a string.
    
    Args:
        expression (str): Mathematical expression (e.g., '2 + 2').
    
    Returns:
        str: Result of the expression.
    """
    try:
        logger.info(f"Evaluating expression: {expression}")
        result = eval(expression, {"__builtins__": {}}, {})  # Safe eval
        if isinstance(result, float):
            return f"{result:.2f}" if "USD" in expression else str(result)
        return str(result)
    except Exception as e:
        logger.error(f"Calculator error: {e}")
        return f"Error: {e}"

calculator_tool = StructuredTool.from_function(
    func=calculator_func,
    name="calculator_tool",
    args_schema=CalculatorInput,
    coroutine=calculator_func
)