"""Atomic file write utilities."""

import json
import logging
import os
import tempfile
from pathlib import Path

logger = logging.getLogger(__name__)


def atomic_write_json(file_path: Path, data: dict, indent: int = 2) -> None:
    """Write JSON data to file atomically via temp file + rename.

    Prevents data corruption if the process crashes or loses power
    mid-write. The rename operation is atomic on most filesystems.
    """
    file_path = Path(file_path)
    file_path.parent.mkdir(parents=True, exist_ok=True)

    # Write to a temp file in the same directory (same filesystem for atomic rename)
    fd, tmp_path = tempfile.mkstemp(
        dir=file_path.parent,
        prefix=f".{file_path.stem}_",
        suffix=".tmp",
    )
    try:
        with os.fdopen(fd, "w", encoding="utf-8") as f:
            json.dump(data, f, indent=indent, ensure_ascii=False)
        os.replace(tmp_path, file_path)
    except BaseException:
        # Clean up temp file on any error
        try:
            os.unlink(tmp_path)
        except OSError as e:
            logger.debug("Failed to clean up temp file %s: %s", tmp_path, e)
            pass
        raise