# grid.py - functions for handling Global Release Identifier (GRid) numbers
#
# 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 GRid (Global Release Identifier) numbers, used to
identify releases of digital sound recordings.

>>> is_valid('A12425GABC1234002M')
True
>>> is_valid('Grid: A1-2425G-ABC1234002-M')
True
>>> is_valid('A1-2425G-ABC1234002-Q') # incorrect check digit
False
>>> is_valid(None) # method should be robust
False
>>> compact('A1-2425G-ABC1234002-M')
'A12425GABC1234002M'
>>> format('A12425GABC1234002M')
'A1-2425G-ABC1234002-M'
"""

def compact(number):
    """Convert the GRid to the minimal representation. This strips the
    number of any valid separators and removes surrounding whitespace."""
    number = number.replace(' ','').replace('-','').strip().upper()
    if number.startswith('GRID:'):
        number = number[5:]
    return number

def is_valid(number):
    """Checks to see if the number provided is a valid GRid."""
    from stdnum import iso7064
    try:
        number = compact(number)
    except:
        return False
    return len(number) == 18 and iso7064.mod_37_36.is_valid(number)

def format(number, separator='-', add_check_digit=False):
    """Reformat the passed number to the standard format."""
    number = compact(number)
    number = ( number[0:2], number[2:7], number[7:17], number[17:] )
    return separator.join(x for x in number if x)