"""Atomic file writes: first a .tmp in the same directory, then os.replace.

A crash leaves at most a .tmp file behind — never a half-written target
file. The .tmp is overwritten on the next successful write.
"""

import json
import os
from pathlib import Path


def atomic_write_text(path: Path, text: str) -> None:
    tmp = path.with_name(path.name + ".tmp")
    with open(tmp, "w", encoding="utf-8") as f:
        f.write(text)
        f.flush()
        os.fsync(f.fileno())
    os.replace(tmp, path)


def atomic_write_json(path: Path, obj, **dumps_kwargs) -> None:
    atomic_write_text(path, json.dumps(obj, ensure_ascii=False, **dumps_kwargs))
