# isan.py - functions for handling International Standard Audiovisual Numbers
#           (ISANs)
#
# Copyright (C) 2010, 2011, 2012 Arthur de Jong
#
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
#
# This library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with this library; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
# 02110-1301 USA

"""ISAN (International Standard Audiovisual Number).

The ISAN (International Standard Audiovisual Number) is used to identify
audiovisual works.

The number is hexadecimal and can consists of at least a root identifier,
and an episode or part. After that an optional check digit, optional
version and optionally another check digit can be provided. The check
digits are validated using the ISO 7064 Mod 37, 36 algorithm.


>>> is_valid('000000018947000000000000')
True
>>> compact('0000-0000-D07A-0090-Q-0000-0000-X')
'00000000D07A009000000000'
>>> is_valid('0000-0001-8CFA-0000-I-0000-0000-K')
True
>>> is_valid('0000-0001-8CFA-0000-A-0000-0000-K') # invalid check digit
False
>>> format('000000018947000000000000')
'0000-0001-8947-0000-8-0000-0000-D'

>>> to_urn('00000000D07A009000000000')
'URN:ISAN:0000-0000-D07A-0090-Q-0000-0000-X'
>>> to_xml('1881-66C7-3420-6541-Y-9F3A-0245-O')
'<ISAN root="1881-66C7-3420" episode="6541" version="9F3A-0245" />'
"""


from stdnum.iso7064 import mod_37_36
from stdnum.util import clean


def split(number):
    """Splits the number into a root, an episode or part, a check digit a
    version and another check digit. If any of the parts are missing an
    empty string is returned."""
    number = clean(number, ' -').strip().upper()
    if len(number) == 17 or len(number) == 26:
        return number[0:12], number[12:16], number[16], number[17:25], number[25:]
    elif len(number) > 16:
        return number[0:12], number[12:16], '', number[16:24], number[24:]
    else:
        return number[0:12], number[12:16], number[16:], '', ''


def compact(number, strip_check_digits=True):
    """Convert the ISAN to the minimal representation. This strips the number
    of any valid separators and removes surrounding whitespace. The check
    digits are also removed by default."""
    number = list(split(number))
    number[2] = number[4] = ''
    return ''.join(number)


def _check(number, length, required=True):
    if (number or required) and length != len(number):
        return False
    for x in number:
        if x not in '0123456789ABCDEF':
            return False
    return True


def is_valid(number):
    """Checks to see if the number provided is a valid ISAN. If check digits
    are present in the number they are validated."""
    try:
        (root, episode, check1, version, check2) = split(number)
        return _check(root, 12) and _check(episode, 4) and _check(version, 8, False) \
           and (not check1 or mod_37_36.is_valid(root + episode + check1)) \
           and (not check2 or mod_37_36.is_valid(root + episode + version + check2))
    except:
        return False


def format(number, separator='-', strip_check_digits=False, add_check_digits=True):
    """Reformat the passed number to the standard format. If
    add_check_digits is True the check digit will be added if they are not
    present yet. If both strip_check_digits and add_check_digits are True the
    check digits will be recalculated."""
    (root, episode, check1, version, check2) = split(number)
    if strip_check_digits:
        check1 = check2 = ''
    if add_check_digits and not check1:
        check1 = mod_37_36.calc_check_digit(root + episode)
    if add_check_digits and not check2 and version:
        check2 = mod_37_36.calc_check_digit(root + episode + version)
    number = [root[i:i + 4] for i in range(0, 12, 4)] + [episode]
    if check1:
        number.append(check1)
    if version:
        number.extend((version[0:4], version[4:]))
    if check2:
        number.append(check2)
    return separator.join(number)


def to_binary(number):
    """Convert the number to it's binary representation (without the check
    digits)."""
    return compact(number, strip_check_digits=True).decode('hex')


def to_xml(number):
    """Returns the XML form of the ISAN as a string."""
    number = format(number, strip_check_digits=True, add_check_digits=False)
    return '<ISAN root="%s" episode="%s" version="%s" />' % (
              number[0:14], number[15:19], number[20:])


def to_urn(number):
    """Returns the URN representation of the ISAN."""
    return 'URN:ISAN:' + format(number, add_check_digits=True)