# SPDX-FileCopyrightText: 2020 The Magma Authors.
# SPDX-FileCopyrightText: 2022 Open Networking Foundation <support@opennetworking.org>
#
# SPDX-License-Identifier: BSD-3-Clause

import codecs
import os


def write_to_file_atomically(filename, value, temp_filename=None):
    """
    Atomically write to a file by first writing the value to a temp file, then
    moving that temp file to the specified file location.

    This function will create all directories necessary for the file as well.

    Args:
        filename: full path to the file to write to
        value: value to write to the file
        temp_filename: requested path of the intermediate temp file
        mode: mode to open the file
    """
    os.makedirs(os.path.dirname(filename), exist_ok=True)
    temp_filename = temp_filename or '{}.tmp'.format(filename)
    with codecs.open(temp_filename, 'w', encoding='utf8') as f:
        f.write(value)
        f.flush()
        os.fsync(f.fileno())
    os.replace(temp_filename, filename)