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

import argparse
import json
import sys
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 provided."""
    text = sys.stdin.read() if path is None or path == "-" else Path(path).read_text(encoding="utf-8")
    return json.loads(text)


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


def run_tests() -> None:
    # Basic object formatting.
    assert pretty_json({"b": 1, "a": 2}, sort_keys=True) == '{\n  "a": 2,\n  "b": 1\n}\n'

    # Nested values and unicode should round-trip cleanly.
    data = {"name": "Ada", "items": [True, None, "π"]}
    assert json.loads(pretty_json(data)) == data


def build_parser() -> argparse.ArgumentParser:
    parser = argparse.ArgumentParser(description="Tiny JSON pretty-printer.")
    parser.add_argument("file", nargs="?", help="JSON file to format; reads stdin when omitted or '-'")
    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 built-in tests")
    return parser


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

    if args.test:
        run_tests()
        return 0

    try:
        value = read_json(args.file)
        sys.stdout.write(pretty_json(value, 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())