"""Module providing Function to generate UUID version 4."""
################################################################################
# The MIT License (MIT)
#
# Author: DerBroader71 (Tudor Davies)
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
#
################################################################################
import os
import struct

def generate_uuid_v4():
    """Function to be called that generates UUIDv4."""
    # Get random bytes from the operating system
    random_bytes = bytearray(os.urandom(16))
    # Set the version number (4 bits) and variant (2 bits)
    random_bytes[6] = (random_bytes[6] & 0x0f) | 0x40
    random_bytes[8] = (random_bytes[8] & 0x3f) | 0x80
    random_bytes = bytes(random_bytes)
    # Format the bytes as a string
    return '{:02x}{:02x}{:02x}{:02x}-{:02x}{:02x}-{:02x}{:02x}-{:02x}{:02x}-{:02x}{:02x}{:02x}{:02x}{:02x}{:02x}'.format(
        *struct.unpack('16B', random_bytes))
