Add support for Singapore Unique Entity Number

Fixes #111.

Author: unho

stdnum/sg/__init__.py

@@ -0,0 +1,22 @@
+# __init__.py - collection of Singapore numbers
+# coding: utf-8
+#
+# Copyright (C) 2020 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 Singapore numbers."""
+from stdnum.sg import uen as vat  # noqa: F401

stdnum/sg/uen.py

@@ -0,0 +1,182 @@
+# uen.py - functions for handling Singapore UEN numbers
+# coding: utf-8
+#
+# Copyright (C) 2020 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
+
+"""UEN (Singapore's Unique Entity Number).
+
+There are four different UEN numbers:
+
+* UEN – Business (ROB): It has a total length of 9 characters. Consists
+  of 8 digits followed by a check letter.
+* UEN – Local Company (ROC): It has a total length of 10 characters.
+  Consists of 9 digits (the 4 leftmost digits represent the year of
+  issuance) followed by a check letter.
+* UEN – Foreign Companies: It has a total length of 10 characters.
+  Begins with the letter F, followed by either 3 zeroes or
+  alternatively 3 whitespaces, then followed by 5 digits, and finally
+  by a check letter.
+* UEN – Others: It has a total length of 10 characters. Begins with
+  either the R letter, or the S letter or the T letter (where R
+  represents '18', S represents '19' and T represents '20') followed by
+  2 digits representing the last two digits of the issuance year. After
+  that come two letters representing the entity type, followed by 4
+  digits, and finally by a check letter.
+
+  For example 'T08' means year 2008, 'S99' means year 1999, and 'R00'
+  means year 1800.
+
+  Entity type must be one of the following:
+    'CC', 'CD', 'CH', 'CL', 'CM', 'CP', 'CS', 'CX', 'DP', 'FB', 'FC',
+    'FM', 'FN', 'GA', 'GB', 'GS', 'HS', 'LL', 'LP', 'MB', 'MC', 'MD',
+    'MH', 'MM', 'MQ', 'NB', 'NR', 'PA', 'PB', 'PF', 'RF', 'RP', 'SM',
+    'SS', 'TC', 'TU', 'VH', 'XL'.
+
+  For example, the UEN for a limited liability partnership (LLP) formed
+  on 1 January 2009 could be 'T09LL0001B'.
+
+More information:
+
+* https://www.oecd.org/tax/automatic-exchange/crs-implementation-and-assistance/tax-identification-numbers/Singapore-TIN.pdf
+* https://www.uen.gov.sg/ueninternet/faces/pages/admin/aboutUEN.jspx
+
+>>> validate('00192200M')
+'00192200M'
+>>> validate('197401143C')
+'197401143C'
+>>> validate('F00056789H')
+'F00056789H'
+>>> validate('F   56789H')
+'F00056789H'
+>>> validate('S16FC0121D')
+'S16FC0121D'
+>>> validate('T01FC6132D')
+'T01FC6132D'
+>>> validate('123456')
+Traceback (most recent call last):
+    ...
+InvalidLength: ...
+>>> format('F   56789H')
+'F00056789H'
+"""
+
+from datetime import datetime
+
+from stdnum.exceptions import *
+from stdnum.util import clean, isdigits
+
+
+OTHER_UEN_ENTITY_TYPES = ('CC', 'CD', 'CH', 'CL', 'CM', 'CP', 'CS', 'CX',
+                          'DP', 'FB', 'FC', 'FM', 'FN', 'GA', 'GB', 'GS',
+                          'HS', 'LL', 'LP', 'MB', 'MC', 'MD', 'MH', 'MM',
+                          'MQ', 'NB', 'NR', 'PA', 'PB', 'PF', 'RF', 'RP',
+                          'SM', 'SS', 'TC', 'TU', 'VH', 'XL')
+
+
+def compact(number):
+    """Convert the number to the minimal representation.
+
+    This converts to uppercase and removes surrounding whitespace. It
+    also replaces the whitespace in UEN for foreign companies with
+    zeroes.
+    """
+    return clean(number).upper().strip().replace(' ', '0')
+
+
+def _validate_business_uen(number):
+    """Perform validation on UEN – Business (ROB) numbers."""
+    if not isdigits(number[:-1]):
+        raise InvalidFormat()
+    if not number[-1].isalpha():
+        raise InvalidFormat()
+
+
+def _validate_local_company_uen(number):
+    """Perform validation on UEN – Local Company (ROC) numbers."""
+    if not isdigits(number[:-1]):
+        raise InvalidFormat()
+    current_year = str(datetime.now().year)
+    if number[:4] > current_year:
+        raise InvalidComponent()
+    if not number[-1].isalpha():
+        raise InvalidFormat()
+
+
+def _validate_foreign_companies_uen(number):
+    """Perform validation on UEN – Foreign Companies numbers."""
+    if number[1:4] not in ('000', '   '):
+        raise InvalidComponent()
+    if not isdigits(number[4:-1]):
+        raise InvalidFormat()
+    if not number[-1].isalpha():
+        raise InvalidFormat()
+
+
+def _validate_other_uen(number):
+    """Perform validation on other UEN numbers."""
+    if number[0] not in ('R', 'S', 'T'):
+        raise InvalidComponent()
+    if not isdigits(number[1:3]):
+        raise InvalidFormat()
+    current_year = str(datetime.now().year)
+    if number[0] == 'T' and number[1:3] > current_year[2:]:
+        raise InvalidComponent()
+    if number[3:5] not in OTHER_UEN_ENTITY_TYPES:
+        raise InvalidComponent()
+    if not isdigits(number[5:-1]):
+        raise InvalidFormat()
+    if not number[-1].isalpha():
+        raise InvalidFormat()
+
+
+def validate(number):
+    """Check if the number is a valid Singapore UEN number.
+
+    This checks the length and formatting.
+    """
+    number = compact(number)
+    if len(number) not in (9, 10):
+        raise InvalidLength()
+    # UEN – Business (ROB).
+    if len(number) == 9:
+        _validate_business_uen(number)
+        return number
+    # UEN – Local Company (ROC).
+    if not number[0].isalpha():
+        _validate_local_company_uen(number)
+        return number
+    # UEN – Foreign Companies.
+    if number[0] == 'F':
+        _validate_foreign_companies_uen(number)
+        return number
+    # UEN – Others.
+    _validate_other_uen(number)
+    return number
+
+
+def is_valid(number):
+    """Check if the number is a valid Singapore UEN number."""
+    try:
+        return bool(validate(number))
+    except ValidationError:
+        return False
+
+
+def format(number):
+    """Reformat the number to the standard presentation format."""
+    return compact(number)