#!/usr/bin/env python3
"""A tiny JSON pretty-printer."""

from __future__ import annotations

import argparse
import json
import sys
import unittest
from pathlib import Path
from typing import Any


def read_json(path: str | None) -> Any:
    """Read JSON from a file path, or stdin when no path is given."""
    if path is None or path == "-":
        return json.load(sys.stdin)

    with Path(path).open("r", encoding="utf-8") as handle:
        return json.load(handle)


def pretty_json(value: Any, indent: int = 2, sort_keys: bool = False) -> str:
    """Return formatted JSON text."""
    return json.dumps(
        value,
        indent=indent,
        sort_keys=sort_keys,
        ensure_ascii=False,
    ) + "\n"


def build_parser() -> argparse.ArgumentParser:
    parser = argparse.ArgumentParser(description="Pretty-print JSON.")
    parser.add_argument("path", nargs="?", help="JSON file to read, or stdin if omitted")
    parser.add_argument("-i", "--indent", type=int, default=2, help="spaces per indent level")
    parser.add_argument("-s", "--sort-keys", action="store_true", help="sort object keys")
    parser.add_argument("--test", action="store_true", help="run tests and exit")
    return parser


class PrettyJsonTests(unittest.TestCase):
    def test_pretty_json_formats_nested_values(self) -> None:
        data: dict[str, Any] = {"name": "Ada", "items": [1, {"ok": True}]}
        expected = '{\n  "name": "Ada",\n  "items": [\n    1,\n    {\n      "ok": true\n    }\n  ]\n}\n'
        self.assertEqual(pretty_json(data), expected)

    def test_pretty_json_can_sort_keys(self) -> None:
        self.assertEqual(pretty_json({"b": 1, "a": 2}, sort_keys=True), '{\n  "a": 2,\n  "b": 1\n}\n')


def run_tests() -> int:
    result = unittest.TextTestRunner(verbosity=2).run(
        unittest.defaultTestLoader.loadTestsFromTestCase(PrettyJsonTests)
    )
    return 0 if result.wasSuccessful() else 1


def main() -> int:
    args = build_parser().parse_args()

    if args.test:
        return run_tests()

    try:
        data = read_json(args.path)
        sys.stdout.write(pretty_json(data, indent=args.indent, sort_keys=args.sort_keys))
    except (OSError, json.JSONDecodeError) as exc:
        print(f"error: {exc}", file=sys.stderr)
        return 1

    return 0


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