"""calc.py — CLI entry point: 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:
        result = evaluate(parse(tokenize(expr)))
    except (LexError, ParseError, EvalError) as e:
        print(f"Error: {e}", file=sys.stderr)
        sys.exit(1)
    print(result)


if __name__ == "__main__":
    main()