# ════════════════════════════════════════════════════════════════
# tools/calculator.py
# ════════════════════════════════════════════════════════════════
"""安全的数学表达式计算工具（AST 解析，防注入）"""

import ast
import operator

from config.settings import settings
from tools.base_tool import BaseTool, ToolResult


class CalculatorTool(BaseTool):
    name        = "calculator"
    description = "计算数学表达式，支持加减乘除、幂运算、括号等"
    parameters  = {
        "expression": {"type": "string", "description": "数学表达式，例如 '(1+2)*3'"},
    }

    _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,
        ast.USub: operator.neg,
    }

    def __init__(self):
        super().__init__()
        # 从配置读取精度
        self._precision = settings.tools['calculator']['precision']
        self.logger.debug(f"⚙️  Calculator 精度: {self._precision}")

    def execute(self, expression: str, **_) -> ToolResult:
        try:
            tree   = ast.parse(expression, mode="eval")
            result = self._eval_node(tree.body)
            result = round(result, self._precision)
            return ToolResult(
                success=True,
                output=f"{expression} = {result}",
                metadata={"expression": expression, "result": result},
            )
        except (ValueError, TypeError, ZeroDivisionError) as exc:
            return ToolResult(success=False, output=f"计算错误: {exc}")

    def _eval_node(self, node: ast.AST) -> float:
        match node:
            case ast.Constant(value=v) if isinstance(v, (int, float)):
                return v
            case ast.BinOp(left=left, op=op, right=right):
                fn = self._OPERATORS.get(type(op))
                if fn is None:
                    raise ValueError(f"不支持的运算符: {type(op).__name__}")
                return fn(self._eval_node(left), self._eval_node(right))
            case ast.UnaryOp(op=op, operand=operand):
                fn = self._OPERATORS.get(type(op))
                if fn is None:
                    raise ValueError(f"不支持的一元运算符: {type(op).__name__}")
                return fn(self._eval_node(operand))
            case _:
                raise ValueError(f"不支持的节点: {type(node).__name__}")