#!/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, TextIO


def load_json(stream: TextIO) -> Any:
    """Read one JSON document from a text stream."""
    return json.load(stream)


def format_json(data: Any, *, indent: int, sort_keys: bool) -> str:
    """Render JSON in a stable, readable form."""
    return json.dumps(data, indent=indent, sort_keys=sort_keys, ensure_ascii=False) + "\n"


def pretty_print(stream: TextIO, *, indent: int = 2, sort_keys: bool = False) -> str:
    """Load JSON from stream and return pretty-printed text."""
    return format_json(load_json(stream), indent=indent, sort_keys=sort_keys)


def build_parser() -> argparse.ArgumentParser:
    parser = argparse.ArgumentParser(description="Pretty-print JSON from a file or stdin.")
    parser.add_argument("file", nargs="?", help="JSON file to read; defaults to stdin")
    parser.add_argument("-i", "--indent", type=int, default=2, help="number of spaces per indent")
    parser.add_argument("-s", "--sort-keys", action="store_true", help="sort object keys")
    parser.add_argument("--test", action="store_true", help="run the built-in tests")
    return parser


class PrettyPrintTests(unittest.TestCase):
    def test_formats_nested_json(self) -> None:
        result = pretty_print(stream_from('{"name":"Ada","items":[1,true,null]}'))
        self.assertEqual(
            result,
            '{\n'
            '  "name": "Ada",\n'
            '  "items": [\n'
            '    1,\n'
            '    true,\n'
            '    null\n'
            '  ]\n'
            '}\n',
        )

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


def stream_from(text: str) -> TextIO:
    # Imported lazily to keep the normal CLI path minimal.
    from io import StringIO

    return StringIO(text)


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

    if args.test:
        suite = unittest.defaultTestLoader.loadTestsFromTestCase(PrettyPrintTests)
        return 0 if unittest.TextTestRunner().run(suite).wasSuccessful() else 1

    try:
        if args.file:
            with Path(args.file).open("r", encoding="utf-8") as stream:
                output = pretty_print(stream, indent=args.indent, sort_keys=args.sort_keys)
        else:
            output = pretty_print(sys.stdin, indent=args.indent, sort_keys=args.sort_keys)
    except (OSError, json.JSONDecodeError) as exc:
        print(f"jsonpp: {exc}", file=sys.stderr)
        return 1

    print(output, end="")
    return 0


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