#!/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
    shout: 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 friendly 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 to print",
    )
    parser.add_argument(
        "-s",
        "--shout",
        action="store_true",
        help="print the greeting in uppercase",
    )
    parser.add_argument(
        "--run-tests",
        action="store_true",
        help="run the built-in tests and exit",
    )
    return parser


def parse_options(argv: Sequence[str] | None = None) -> Options:
    args = build_parser().parse_args(argv)
    return Options(
        name=args.name,
        count=args.count,
        shout=args.shout,
        run_tests=args.run_tests,
    )


def make_greeting(name: str, shout: bool = False) -> str:
    greeting = f"Hello, {name}!"
    return greeting.upper() if shout else greeting


def run_cli(options: Options, stdout: TextIO = sys.stdout) -> int:
    # Keep output logic separate so it is easy to test.
    for _ in range(options.count):
        print(make_greeting(options.name, options.shout), file=stdout)
    return 0


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

    def test_custom_arguments(self) -> None:
        self.assertEqual(
            parse_options(["Ada", "--count", "2", "--shout"]),
            Options(name="Ada", count=2, shout=True, run_tests=False),
        )


def main(argv: Sequence[str] | None = None) -> int:
    options = parse_options(argv)
    if options.run_tests:
        suite = unittest.defaultTestLoader.loadTestsFromTestCase(ParserTests)
        result = unittest.TextTestRunner(verbosity=2).run(suite)
        return 0 if result.wasSuccessful() else 1
    return run_cli(options)


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