#-----------------------------------------------------------------------------
#   Copyright (c) 2008-2015, David P. D. Moss. All rights reserved.
#
#   Released under the BSD license. See the LICENSE file for details.
#-----------------------------------------------------------------------------
"""
IPv6 address logic.
"""
import struct as _struct

OPT_IMPORTS = False

#   Check whether we need to use fallback code or not.
try:
    import socket as _socket
    #   These might all generate exceptions on different platforms.
    if not _socket.has_ipv6:
        raise Exception('IPv6 disabled')
    _socket.inet_pton
    _socket.AF_INET6
    from _socket import (inet_pton as _inet_pton, inet_ntop as _inet_ntop,
                         AF_INET6)
    OPT_IMPORTS = True
except Exception:
    from netaddr.fbsocket import (inet_pton as _inet_pton, inet_ntop as _inet_ntop,
                                 AF_INET6)

from netaddr.core import AddrFormatError
from netaddr.strategy import (
    valid_words as _valid_words, int_to_words as _int_to_words,
    words_to_int as _words_to_int, valid_bits as _valid_bits,
    bits_to_int as _bits_to_int, int_to_bits as _int_to_bits,
    valid_bin as _valid_bin, int_to_bin as _int_to_bin,
    bin_to_int as _bin_to_int)

#: The width (in bits) of this address type.
width = 128

#: The individual word size (in bits) of this address type.
word_size = 16

#: The separator character used between each word.
word_sep = ':'

#: The AF_* constant value of this address type.
family = AF_INET6

#: A friendly string name address type.
family_name = 'IPv6'

#: The version of this address type.
version = 6

#: The number base to be used when interpreting word values as integers.
word_base = 16

#: The maximum integer value that can be represented by this address type.
max_int = 2 ** width - 1

#: The number of words in this address type.
num_words = width // word_size

#: The maximum integer value for an individual word in this address type.
max_word = 2 ** word_size - 1

#: A dictionary mapping IPv6 CIDR prefixes to the equivalent netmasks.
prefix_to_netmask = dict(
    [(i, max_int ^ (2 ** (width - i) - 1)) for i in range(0, width+1)])

#: A dictionary mapping IPv6 netmasks to their equivalent CIDR prefixes.
netmask_to_prefix = dict(
    [(max_int ^ (2 ** (width - i) - 1), i) for i in range(0, width+1)])

#: A dictionary mapping IPv6 CIDR prefixes to the equivalent hostmasks.
prefix_to_hostmask = dict(
    [(i, (2 ** (width - i) - 1)) for i in range(0, width+1)])

#: A dictionary mapping IPv6 hostmasks to their equivalent CIDR prefixes.
hostmask_to_prefix = dict(
    [((2 ** (width - i) - 1), i) for i in range(0, width+1)])

#-----------------------------------------------------------------------------
#   Dialect classes.
#-----------------------------------------------------------------------------

class ipv6_compact(object):
    """An IPv6 dialect class - compact form."""
    #: The format string used to converting words into string values.
    word_fmt = '%x'

    #: Boolean flag indicating if IPv6 compaction algorithm should be used.
    compact = True

class ipv6_full(ipv6_compact):
    """An IPv6 dialect class - 'all zeroes' form."""

    #: Boolean flag indicating if IPv6 compaction algorithm should be used.
    compact = False

class ipv6_verbose(ipv6_compact):
    """An IPv6 dialect class - extra wide 'all zeroes' form."""

    #: The format string used to converting words into string values.
    word_fmt = '%.4x'

    #: Boolean flag indicating if IPv6 compaction algorithm should be used.
    compact = False


def valid_str(addr, flags=0):
    """
    :param addr: An IPv6 address in presentation (string) format.

    :param flags: decides which rules are applied to the interpretation of the
        addr value. Future use - currently has no effect.

    :return: ``True`` if IPv6 address is valid, ``False`` otherwise.
    """
    if addr == '':
        raise AddrFormatError('Empty strings are not supported!')

    try:
        _inet_pton(AF_INET6, addr)
    except:
        return False
    return True


def str_to_int(addr, flags=0):
    """
    :param addr: An IPv6 address in string form.

    :param flags: decides which rules are applied to the interpretation of the
        addr value. Future use - currently has no effect.

    :return: The equivalent unsigned integer for a given IPv6 address.
    """
    try:
        packed_int = _inet_pton(AF_INET6, addr)
        return packed_to_int(packed_int)
    except Exception:
        raise AddrFormatError('%r is not a valid IPv6 address string!' % addr)


def int_to_str(int_val, dialect=None):
    """
    :param int_val: An unsigned integer.

    :param dialect: (optional) a Python class defining formatting options.

    :return: The IPv6 presentation (string) format address equivalent to the
        unsigned integer provided.
    """
    if dialect is None:
        dialect = ipv6_compact

    addr = None

    try:
        packed_int = int_to_packed(int_val)
        if dialect.compact:
            #   Default return value.
            addr = _inet_ntop(AF_INET6, packed_int)
        else:
            #   Custom return value.
            words = list(_struct.unpack('>8H', packed_int))
            tokens = [dialect.word_fmt % word for word in words]
            addr = word_sep.join(tokens)
    except Exception:
        raise ValueError('%r is not a valid 128-bit unsigned integer!' % int_val)

    return addr


def int_to_arpa(int_val):
    """
    :param int_val: An unsigned integer.

    :return: The reverse DNS lookup for an IPv6 address in network byte
        order integer form.
    """
    addr = int_to_str(int_val, ipv6_verbose)
    tokens = list(addr.replace(':', ''))
    tokens.reverse()
    #   We won't support ip6.int here - see RFC 3152 for details.
    tokens = tokens + ['ip6', 'arpa', '']
    return '.'.join(tokens)


def int_to_packed(int_val):
    """
    :param int_val: the integer to be packed.

    :return: a packed string that is equivalent to value represented by an
    unsigned integer.
    """
    words = int_to_words(int_val, 4, 32)
    return _struct.pack('>4I', *words)


def packed_to_int(packed_int):
    """
    :param packed_int: a packed string containing an unsigned integer.
        It is assumed that string is packed in network byte order.

    :return: An unsigned integer equivalent to value of network address
        represented by packed binary string.
    """
    words = list(_struct.unpack('>4I', packed_int))

    int_val = 0
    for i, num in enumerate(reversed(words)):
        word = num
        word = word << 32 * i
        int_val = int_val | word

    return int_val


def valid_words(words):
    return _valid_words(words, word_size, num_words)


def int_to_words(int_val, num_words=None, word_size=None):
    if num_words is None:
        num_words = globals()['num_words']
    if word_size is None:
        word_size = globals()['word_size']
    return _int_to_words(int_val, word_size, num_words)


def words_to_int(words):
    return _words_to_int(words, word_size, num_words)


def valid_bits(bits):
    return _valid_bits(bits, width, word_sep)


def bits_to_int(bits):
    return _bits_to_int(bits, width, word_sep)


def int_to_bits(int_val, word_sep=None):
    if word_sep is None:
        word_sep = globals()['word_sep']
    return _int_to_bits(int_val, word_size, num_words, word_sep)


def valid_bin(bin_val):
    return _valid_bin(bin_val, width)


def int_to_bin(int_val):
    return _int_to_bin(int_val, width)


def bin_to_int(bin_val):
    return _bin_to_int(bin_val, width)
