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

import argparse
import json
import sys
from pathlib import Path
from typing import Any, TextIO


def format_json(text: str, *, indent: int = 2, sort_keys: bool = False) -> str:
    """Parse JSON text and return a pretty-printed version."""
    data: Any = json.loads(text)
    return json.dumps(data, indent=indent, sort_keys=sort_keys, ensure_ascii=False) + "\n"


def read_input(path: str | None, stdin: TextIO) -> str:
    # Missing path or "-" means stdin, matching common command-line tools.
    if path is None or path == "-":
        return stdin.read()
    return Path(path).read_text(encoding="utf-8")


def run_tests() -> None:
    assert format_json('{"b":2,"a":[1,true,null]}') == (
        '{\n'
        '  "b": 2,\n'
        '  "a": [\n'
        '    1,\n'
        '    true,\n'
        '    null\n'
        '  ]\n'
        '}\n'
    )
    assert format_json('{"b":2,"a":1}', sort_keys=True) == (
        '{\n'
        '  "a": 1,\n'
        '  "b": 2\n'
        '}\n'
    )


def build_parser() -> argparse.ArgumentParser:
    parser = argparse.ArgumentParser(description="Pretty-print JSON from a file or stdin.")
    parser.add_argument("path", nargs="?", help="JSON file to read, or '-' for stdin")
    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 basic self-tests")
    return parser


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

    if args.test:
        run_tests()
        print("tests passed", file=sys.stderr)
        return 0

    try:
        text = read_input(args.path, sys.stdin)
        sys.stdout.write(format_json(text, indent=args.indent, sort_keys=args.sort_keys))
    except (OSError, json.JSONDecodeError, ValueError) as exc:
        print(f"error: {exc}", file=sys.stderr)
        return 1

    return 0


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