Add support for Philippines TIN

Fixes arthurdejong#116

stdnum/ph/__init__.py

@@ -0,0 +1,24 @@
+# __init__.py - collection of Philippines 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 Philippines numbers."""
+
+# provide aliases
+from stdnum.ph import tin as vat  # noqa: F401

stdnum/ph/tin.py

@@ -0,0 +1,114 @@
+# nit.py - functions for handling Philippines TIN 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
+
+"""TIN (Taxpayer Identification Number, Philippines tax number).
+
+This number consists of 9 digits (for individual taxpayers), or 12 digits (for
+bussinesses). A thirteenth digit will be added in the future for businesses).
+It is usually separated using hyphens to make it easier to read, like
+XXX-XXX-XXX-XXX.
+
+The first digit identifies the type of taxpayer: 0 for businesses and 1 to 9
+for individual taxpayers. The following seven digits are a sequence. The ninth
+digit is the check digit.
+
+The last three digits (four in the future), for businesses only, correspond to
+the branch code. If the branch code is not specified, then it defaults to 000.
+
+It is not specified in the official documents, but it is not uncommon that some
+letters are appended to the businesses TIN to tell whether it is subject to
+VAT, usually N to say it is not subject and V to tell that it is.
+
+More information:
+
+* https://www.ntrc.gov.ph/images/journal/j20141112a.pdf
+* https://wiki.scn.sap.com/wiki/display/CRM/Philippines
+* https://help.sap.com/doc/saphelp_erp2005/6.0/ja-JP/d8/663e399265df0ee10000000a11402f/content.htm
+* https://world.salestaxhandbook.com/ph-philippines
+
+>>> validate('239-072-842')
+'239072842'
+>>> validate('239-072-842-000')
+'239072842000'
+>>> validate('12345')
+Traceback (most recent call last):
+    ...
+InvalidLength: ...
+>>> validate('12345678X')
+Traceback (most recent call last):
+    ...
+InvalidFormat: ...
+>>> format('239072842000')
+'239-072-842-000'
+"""  # noqa: E501
+
+from stdnum.exceptions import *
+from stdnum.util import clean, isdigits
+
+
+def compact(number):
+    """Convert the number to the minimal representation.
+
+    This strips the number of any valid separators and removes surrounding
+    whitespace.
+    """
+    number = clean(number, ' -').upper().strip()
+    # Normalize unofficial code telling whether it is subject or not to VAT.
+    number = number.replace('NONVAT', 'N')
+    number = number.replace('NVAT', 'N')
+    number = number.replace('NV', 'N')
+    number = number.replace('VAT', 'V')
+    # Append the default branch code for business TIN numbers having unofficial
+    # VAT letter.
+    if len(number) == 10 and number[-1] in ('N', 'V'):
+        number = number[:-1] + '000' + number[-1]
+    return number
+
+
+def validate(number):
+    """Check if the number is a valid Philippines TIN number.
+
+    This checks the length and formatting.
+    """
+    number = compact(number)
+    if len(number) not in (9, 12, 13, 14):
+        raise InvalidLength()
+    has_wrong_format = not (isdigits(number) or
+                            (number[-1] in ('N', 'V') and
+                             isdigits(number[:-1])))
+    if has_wrong_format:
+        raise InvalidFormat()
+    return number
+
+
+def is_valid(number):
+    """Check if the number is a valid Philippines TIN number."""
+    try:
+        return bool(validate(number))
+    except ValidationError:
+        return False
+
+
+def format(number):
+    """Reformat the number to the standard presentation format."""
+    number = compact(number)
+    if len(number) < 12:
+        return '-'.join([number[:3], number[3:6], number[6:]])
+    return '-'.join([number[:3], number[3:6], number[6:9], number[9:]])