import ipaddress
import dns.name

def reverse_zone(network):
    """
    Reverse a network zone

    Takes an network object (`ipaddress.IPv4Network` or
    `ipaddress.IPv6Network`) as an input and returns a DNS name object
    (`dns.name.Name`) corresponding to the reverse DNS entry correctly
    formated.

    Parameters
    ----------
    network: ipaddress.IPv4Network or ipaddress.IPv6Network
        The Network IP and mask object

    Return
    ------
    reversed_zone: dns.name.Name
        The reverse zone as a DNS Name oject

    Examples
    --------
    >>> # Some IPv4 Networks
    >>> net1 = ipaddress.IPv4Network("10.128.12.0/24")
    >>> net2 = ipaddress.IPv4Network("10.129.0.0/16")
    >>> net3 = ipaddress.IPv4Network("10.0.0.0/8")
    >>> # Some IPv6 Networks
    >>> net4 = ipaddress.IPv6Network("2001:470:142:3::/64")
    >>> net5 = ipaddress.IPv6Network("2001:470:142::/48")
    >>> net6 = ipaddress.IPv6Network("2a09:6840::/32")
    >>> # And the expected outputs
    >>> reverse_zone(net1)
    '12.128.10.in-addr.arpa'
    >>> reverse_zone(net2)
    '129.10.in-addr.arpa'
    >>> reverse_zone(net3)
    '10.in-addr.arpa'
    >>> reverse_zone(net4)
    '3.0.0.0.2.4.1.0.0.7.4.0.1.0.0.2.ip6.arpa'
    >>> reverse_zone(net5)
    '2.4.1.0.0.7.4.0.1.0.0.2.ip6.arpa'
    >>> reverse_zone(net6)
    '0.4.8.6.9.0.a.2.ip6.arpa'

    See also
    --------
    dnspython: https://dnspython.readthedocs.io
    ipaddress: https://docs.python.org/3/library/ipaddress.html

    References
    ----------
    [1] RFC 1035: DOMAIN NAMES - IMPLEMENTATION AND SPECIFICATION,
    IETF, Network Working Group, November 1987.
    """

    if network.version == 4:
        boundary = 8  # break to the byte
    elif network.version == 6:
        boundary = 4  # break to the nibble

    assert network.prefixlen % boundary == 0
    length = (network.prefixlen // boundary)

    full_network_reverse = network.network_address.reverse_pointer

    splitted = full_network_reverse.split(".")
    splitting_len = int(network.max_prefixlen / boundary)
    splitted = splitted[splitting_len - length:]

    reversed_zone = ".".join(splitted)

    return dns.name.from_text(reversed_zone)