"""Publish complete files without replacing a usable file after a failed write."""
from contextlib import contextmanager
import os
from pathlib import Path
import tempfile


@contextmanager
def atomic_output(path, mode="wb"):
    path = Path(path)
    path.parent.mkdir(parents=True, exist_ok=True)
    handle = tempfile.NamedTemporaryFile(mode=mode, dir=path.parent,
        prefix=path.name + ".", suffix=".partial", delete=False,
        **({"encoding": "utf-8"} if "b" not in mode else {}))
    temporary = Path(handle.name)
    try:
        with handle:
            yield handle
            handle.flush()
            os.fsync(handle.fileno())
        os.replace(temporary, path)
        if os.name != "nt":
            descriptor = os.open(path.parent, os.O_RDONLY)
            try:
                os.fsync(descriptor)
            finally:
                os.close(descriptor)
    finally:
        temporary.unlink(missing_ok=True)