91 lines
3.2 KiB
Python
91 lines
3.2 KiB
Python
# at_02.py - functions for handling AT-02 (SEPA Creditor identifier)
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#
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# Copyright (C) 2014-2016 Sergi Almacellas Abellana
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#
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# This library is free software; you can redistribute it and/or
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# modify it under the terms of the GNU Lesser General Public
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# License as published by the Free Software Foundation; either
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# version 2.1 of the License, or (at your option) any later version.
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#
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# This library is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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# Lesser General Public License for more details.
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#
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# You should have received a copy of the GNU Lesser General Public
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# License along with this library; if not, write to the Free Software
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# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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# 02110-1301 USA
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"""SEPA Identifier of the Creditor (AT-02).
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This identifier is indicated in the ISO 20022 data element `Creditor Scheme
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Identification`. The creditor can be a legal entity, or an association that
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is not a legal entity, or a person.
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The first two digits contain the ISO country code, the next two are check
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digits for the ISO 7064 Mod 97, 10 checksum, the next tree contain the
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Creditor Business Code (or `ZZZ` if no business code used) and the remainder
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contains the country-specific identifier.
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>>> validate('ES 23 ZZZ 47690558N')
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'ES23ZZZ47690558N'
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>>> validate('ES2300047690558N')
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'ES2300047690558N'
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>>> compact('ES++()+23ZZZ4//7690558N')
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'ES23ZZZ47690558N'
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>>> calc_check_digits('ESXXZZZ47690558N')
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'23'
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"""
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from __future__ import annotations
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from stdnum.exceptions import *
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from stdnum.iso7064 import mod_97_10
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from stdnum.util import clean
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# the valid characters we have
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_alphabet = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ'
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def compact(number: str) -> str:
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"""Convert the AT-02 number to the minimal representation. This strips
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the number of any valid separators and removes invalid characters."""
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return clean(number, ' -/?:().m\'+"').strip().upper()
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def _to_base10(number: str) -> str:
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"""Prepare the number to its base10 representation so it can be checked
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with the ISO 7064 Mod 97, 10 algorithm. That means excluding positions 5
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to 7 and moving the first four digits to the end."""
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return ''.join(str(_alphabet.index(x)) for x in number[7:] + number[:4])
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def validate(number: str) -> str:
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"""Check if the number provided is a valid AT-02."""
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number = compact(number)
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try:
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test_number = _to_base10(number)
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except Exception: # noqa: B902
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raise InvalidFormat()
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# ensure that checksum is valid
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mod_97_10.validate(test_number)
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return number
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def is_valid(number: str) -> bool:
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"""Check if the number provided is a valid AT-02."""
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try:
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return bool(validate(number))
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except ValidationError:
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return False
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def calc_check_digits(number: str) -> str:
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"""Calculate the check digits that should be put in the number to make it
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valid. Check digits in the supplied number are ignored."""
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number = compact(number)
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# replace check digits with placeholders
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number = ''.join((number[:2], '00', number[4:]))
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return mod_97_10.calc_check_digits(_to_base10(number)[:-2])
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