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# ogm_vcs.py - functions for handling Belgian OGM-VCS
# coding: utf-8
#
# Copyright (C) 2025 Cédric Krier
#
# 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
"""Belgian OGM-VCS.
The OGM-VCS is used in bank transfer as structured communication.
* https://febelfin.be/en/publications/2023/febelfin-banking-standards-for-online-banking
>>> validate('+++010/8068/17183+++')
'010806817183'
>>> validate('010/8068/17180')
Traceback (most recent call last):
...
InvalidChecksum: ...
>>> format('010806817183')
'010/8068/17183'
>>> calc_check_digits('0108068171')
'83'
"""
from __future__ import annotations
from stdnum.exceptions import *
from stdnum.util import clean, isdigits
def compact(number: str) -> str:
"""Convert the number to the minimal representation. This strips the number
of any invalid separators and removes surrounding whitespace."""
return clean(number, ' +/').strip()
def calc_check_digits(number: str) -> str:
"""Calculate the check digit that should be added."""
number = compact(number)
return '%02d' % ((int(number[:10]) % 97) or 97)
def validate(number: str) -> str:
"""Check if the number is a valid OGM-VCS."""
number = compact(number)
if not isdigits(number) or int(number) <= 0:
raise InvalidFormat()
if len(number) != 12:
raise InvalidLength()
if calc_check_digits(number) != number[-2:]:
raise InvalidChecksum()
return number
def is_valid(number: str) -> bool:
"""Check if the number is a valid VAT number."""
try:
return bool(validate(number))
except ValidationError:
return False
def format(number: str) -> str:
"""Format the number provided for output."""
number = compact(number)
number = number.rjust(12, '0')
return f'{number[:3]}/{number[3:7]}/{number[7:]}'
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