Add support for Panama TIN

Note this only adds support for the legal person's TIN number.

Closes arthurdejong#102

Author: unho

Diff for: stdnum/pa/__init__.py

@@ -0,0 +1,24 @@
+# __init__.py - collection of Panamanian numbers
+# coding: utf-8
+#
+# Copyright (C) 2023 Leandro Regueiro
+#
+# 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
+
+"""Collection of Panamanian numbers."""
+
+# provide aliases
+from stdnum.pa import ruc as vat  # noqa: F401

Diff for: stdnum/pa/ruc.py

@@ -0,0 +1,167 @@
+# ruc.py - functions for handling Panama RUC numbers
+# coding: utf-8
+#
+# Copyright (C) 2023 Leandro Regueiro
+#
+# 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
+
+"""RUC (Registro Único del Contribuyente, Panama tax number).
+
+The Registro Único del Contribuyente (RUC) is an identifier of legal entities
+for tax purposes.
+
+This number has different variants both for natural and legal persons, each
+with its own structure, but basically it consists on a number of digits and
+letters (only for natural persons) usually separated by hyphens (the number and
+position of these varies according to the variant), then followed by a check
+number (dígito verificador) consisting in up to two digits.
+
+More information:
+
+* https://www.oecd.org/tax/automatic-exchange/crs-implementation-and-assistance/tax-identification-numbers/Panama-TIN.pdf
+* https://studylib.es/doc/545131/algoritmo-para-el-calculo-del-digito-verificador-de-la-ru
+
+>>> validate('253-92-57027 DV 76')
+'00000002530092057027DV76'
+>>> validate('155587169-2-2014    D.V. 9')
+'01555871690002002014DV09'
+>>> validate('253-92-57027 DV 23')
+Traceback (most recent call last):
+    ...
+InvalidChecksum: ...
+>>> validate('12345678')
+Traceback (most recent call last):
+    ...
+InvalidLength: ...
+>>> format('253-92-57027 DV 76')
+'0000000253-0092-057027 DV76'
+"""  # noqa: E501
+
+from stdnum.exceptions import *
+from stdnum.util import clean, isdigits
+
+
+ARRVAL = {
+    '00': '00',
+    '10': '01',
+    '11': '02',
+    '12': '03',
+    '13': '04',
+    '14': '05',
+    '15': '06',
+    '16': '07',
+    '17': '08',
+    '18': '09',
+    '19': '01',
+    '20': '02',
+    '21': '03',
+    '22': '04',
+    '23': '07',
+    '24': '08',
+    '25': '09',
+    '26': '02',
+    '27': '03',
+    '28': '04',
+    '29': '05',
+    '30': '06',
+    '31': '07',
+    '32': '08',
+    '33': '09',
+    '34': '01',
+    '35': '02',
+    '36': '03',
+    '37': '04',
+    '38': '05',
+    '39': '06',
+    '40': '07',
+    '41': '08',
+    '42': '09',
+    '43': '01',
+    '44': '02',
+    '45': '03',
+    '46': '04',
+    '47': '05',
+    '48': '06',
+    '49': '07',
+}
+
+
+def compact(number):
+    """Convert the number to the minimal representation.
+
+    This strips the number of any valid separators and removes surrounding
+    whitespace.
+    """
+    parts = clean(number, ' .').strip().upper().split('-')
+
+    # We can currently only compact legal person's RUC numbers with check digit.
+    if len(parts) != 3 or len(parts[0]) in (1, 2) or 'DV' not in parts[2]:
+        return ''
+
+    parts[2], dv = parts[2].split('DV')
+
+    return ''.join([parts[0].zfill(10), parts[1].zfill(4),
+                    parts[2].strip().zfill(6), 'DV', dv.strip().zfill(2)])
+
+
+def calc_check_digit(number, is_old_legal_ruc):
+    """Calculate the check digit."""
+    if is_old_legal_ruc:
+        weights = list(range(2, 12)) + list(range(11, len(number) + 1))
+    else:
+        weights = list(range(2, len(number) + 2))
+    total = sum(int(n) * w for w, n in zip(weights, reversed(number)))
+    r = total % 11
+    return str(11 - r) if r > 1 else '0'
+
+
+def validate(number):
+    """Check if the number is a valid Panama RUC number.
+
+    This checks the length, formatting and check digits.
+    """
+    number = compact(number)
+    if len(number) != 24:
+        raise InvalidLength()
+    if not isdigits(number[:-4]) or not isdigits(number[-2:]):
+        raise InvalidComponent()
+    if number[-4:-2] != 'DV':
+        raise InvalidComponent()
+    is_old_legal_ruc = number[3:6] in ('000', '001', '002', '003', '004')
+    if is_old_legal_ruc and number[5:7] in ARRVAL:
+        number = number[:5] + ARRVAL[number[5:7]] + number[7:]
+    dv1 = calc_check_digit(number[:-4], is_old_legal_ruc)
+    if number[-2] != dv1:
+        raise InvalidChecksum()
+    dv2 = calc_check_digit(number[:-4] + dv1, is_old_legal_ruc)
+    if number[-1] != dv2:
+        raise InvalidChecksum()
+    return number
+
+
+def is_valid(number):
+    """Check if the number is a valid Panama RUC number."""
+    try:
+        return bool(validate(number))
+    except ValidationError:
+        return False
+
+
+def format(number):
+    """Reformat the number to the standard presentation format."""
+    number = compact(number)
+    return ''.join([number[:10], '-', number[10:14], '-', number[14:-4], ' ',
+                    number[-4:]])