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

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


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


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

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


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 times to print the greeting",
    )
    parser.add_argument(
        "-u",
        "--uppercase",
        action="store_true",
        help="print the greeting in uppercase",
    )
    return parser


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


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


def main(argv: Sequence[str] | None = None, stdout: TextIO = sys.stdout) -> int:
    options = parse_options(sys.argv[1:] if argv is None else argv)
    print(render_greeting(options), file=stdout)
    return 0


class CliTests(unittest.TestCase):
    def test_defaults(self) -> None:
        self.assertEqual(parse_options([]), Options(name="world", count=1, uppercase=False))

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


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