#!/usr/bin/env python3

import argparse
from typing import Optional, Sequence


def positive_int(value: str) -> int:
    """Convert a string to a positive integer."""
    number = int(value)
    if number < 1:
        raise argparse.ArgumentTypeError("must be a positive integer")
    return number


def build_parser() -> argparse.ArgumentParser:
    """Create the command-line argument parser."""
    parser = argparse.ArgumentParser(description="Print a friendly greeting.")
    parser.add_argument("name", help="name of the person to greet")
    parser.add_argument(
        "-n",
        "--times",
        type=positive_int,
        default=1,
        help="number of greetings to print (default: 1)",
    )
    parser.add_argument(
        "-u",
        "--uppercase",
        action="store_true",
        help="print the greeting in uppercase",
    )
    return parser


def format_greeting(name: str, uppercase: bool = False) -> str:
    """Return a greeting.

    >>> format_greeting("Ada")
    'Hello, Ada!'
    >>> format_greeting("Ada", uppercase=True)
    'HELLO, ADA!'
    """
    greeting = f"Hello, {name}!"
    return greeting.upper() if uppercase else greeting


def main(argv: Optional[Sequence[str]] = None) -> int:
    """Parse arguments and run the CLI."""
    args = build_parser().parse_args(argv)
    greeting = format_greeting(args.name, args.uppercase)

    for _ in range(args.times):
        print(greeting)

    return 0


if __name__ == "__main__":
    raise SystemExit(main())