#!/usr/bin/env python3
"""calc.py — command-line arithmetic calculator.

Usage: python calc.py "<expression>"
"""

import sys

from calc.evaluator import EvalError, evaluate
from calc.lexer import LexError, tokenize
from calc.parser import ParseError, parse


def main():
    if len(sys.argv) != 2:
        print("Usage: calc.py <expression>", file=sys.stderr)
        sys.exit(1)

    expr = sys.argv[1]
    try:
        tokens = tokenize(expr)
        ast = parse(tokens)
        result = evaluate(ast)
        print(result)
    except (LexError, ParseError, EvalError) as e:
        print(f"Error: {e}", file=sys.stderr)
        sys.exit(1)


if __name__ == '__main__':
    main()