#!/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
    excited: bool
    run_tests: bool


def positive_int(value: str) -> int:
    number = int(value)
    if number < 1:
        raise argparse.ArgumentTypeError("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("-c", "--count", type=positive_int, default=1, help="number of greetings")
    parser.add_argument("--excited", action="store_true", help="add an exclamation mark")
    parser.add_argument("--run-tests", action="store_true", help="run parser tests and exit")
    return parser


def parse_args(argv: Sequence[str]) -> Options:
    args = build_parser().parse_args(argv)
    return Options(
        name=args.name,
        count=args.count,
        excited=args.excited,
        run_tests=args.run_tests,
    )


def render_greeting(options: Options) -> str:
    punctuation = "!" if options.excited else "."
    return "\n".join(f"Hello, {options.name}{punctuation}" for _ in range(options.count))


def main(argv: Sequence[str] | None = None) -> int:
    options = parse_args(sys.argv[1:] if argv is None else argv)

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

    print(render_greeting(options))
    return 0


class ParserTests(unittest.TestCase):
    def test_defaults(self) -> None:
        self.assertEqual(parse_args([]), Options("world", 1, False, False))

    def test_custom_values(self) -> None:
        self.assertEqual(parse_args(["Ada", "--count", "2", "--excited"]), Options("Ada", 2, True, False))


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