#!/usr/bin/env python3
from __future__ import annotations

import argparse
import sys
import unittest
from dataclasses import dataclass
from typing import Sequence


@dataclass(frozen=True)
class Options:
    name: str
    count: int
    shout: bool


def positive_int(value: str) -> int:
    """Parse a positive integer for argparse."""
    try:
        number = int(value)
    except ValueError as exc:
        raise argparse.ArgumentTypeError(f"{value!r} is not an integer") from exc

    if number < 1:
        raise argparse.ArgumentTypeError("value must be at least 1")
    return number


def build_parser() -> argparse.ArgumentParser:
    parser = argparse.ArgumentParser(description="Print a configurable greeting.")
    parser.add_argument("name", nargs="?", default="world", help="name to greet")
    parser.add_argument("-n", "--count", type=positive_int, default=1, help="number of greetings")
    parser.add_argument("--shout", action="store_true", help="print the greeting in uppercase")
    parser.add_argument("--self-test", action="store_true", help=argparse.SUPPRESS)
    return parser


def options_from_args(args: argparse.Namespace) -> Options:
    return Options(name=args.name, count=args.count, shout=args.shout)


def render_greeting(options: Options) -> str:
    greeting = f"Hello, {options.name}!"
    if options.shout:
        greeting = greeting.upper()

    # Repeat by joining lines so output has no extra trailing newline.
    return "\n".join(greeting for _ in range(options.count))


def main(argv: Sequence[str] | None = None) -> int:
    parser = build_parser()
    args = parser.parse_args(argv)

    if args.self_test:
        suite = unittest.defaultTestLoader.loadTestsFromTestCase(ParserTests)
        result = unittest.TextTestRunner(verbosity=2).run(suite)
        return 0 if result.wasSuccessful() else 1

    print(render_greeting(options_from_args(args)))
    return 0


class ParserTests(unittest.TestCase):
    def test_defaults(self) -> None:
        args = build_parser().parse_args([])
        self.assertEqual(options_from_args(args), Options(name="world", count=1, shout=False))

    def test_render_repeated_shout(self) -> None:
        output = render_greeting(Options(name="Ada", count=2, shout=True))
        self.assertEqual(output, "HELLO, ADA!\nHELLO, ADA!")


if __name__ == "__main__":
    raise SystemExit(main(sys.argv[1:]))