# isan.py - functions for handling International Standard Audiovisual Numbers
#           (ISANs)
#
# Copyright (C) 2010 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

"""Module for handling ISANs (International Standard Audiovisual Numbers),
used to identify audiovisual works.

>>> 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 import iso7064


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 = number.replace(' ','').replace('-','').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 iso7064.mod_37_36.is_valid(root+episode+check1) ) \
           and ( not check2 or iso7064.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 = iso7064.mod_37_36.calc_check_digit(root+episode)
    if add_check_digits and not check2 and version:
        check2 = iso7064.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)