"""CLI entry point: python calc.py "<expression>" """

import sys

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


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()