Add support for Hong Kong TIN

Fixes #320.

Author: unho

stdnum/hk/__init__.py

@@ -0,0 +1,24 @@
+# __init__.py - collection of Hong Kong numbers
+# coding: utf-8
+#
+# Copyright (C) 2022 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 Hong Kong numbers."""
+
+# provide aliases
+from stdnum.hk import brn as vat  # noqa: F401

stdnum/hk/brn.py

@@ -0,0 +1,84 @@
+# nit.py - functions for handling Hong Kong BR numbers
+# coding: utf-8
+#
+# Copyright (C) 2022 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
+
+"""BRN (Bussiness Registration number, Hong Kong tax number).
+
+Sometimes also called "商業登記號碼" or "BR No."
+
+This number consists of 8 digits. It is the first 8 digits at the front of the
+Business Registration Certificate Number, which in turn has the
+22222222-XXX-XX-XX-X format. It is provided by the Inland Revenue Department
+(IRD) of Hong Kong at the date of incorporation.
+
+More information:
+
+* https://www.oecd.org/tax/automatic-exchange/crs-implementation-and-assistance/tax-identification-numbers/Hong-Kong-TIN.pdf
+* https://sleek.com/hk/resources/hong-kong-business-registration-number-vs-company-registration-number/
+* https://blog.startupr.hk/hong-kong-business-registration-number-brn/
+
+>>> validate('31130878')
+'31130878'
+>>> validate('1767 4094')
+'17674094'
+>>> validate('12345')
+Traceback (most recent call last):
+    ...
+InvalidLength: ...
+>>> format('1767 4094')
+'17674094'
+"""  # 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.
+    """
+    return clean(number, ' -')
+
+
+def validate(number):
+    """Check if the number is a valid Hong Kong BR number.
+
+    This checks the length and formatting.
+    """
+    number = compact(number)
+    if len(number) != 8:
+        raise InvalidLength()
+    if not isdigits(number):
+        raise InvalidFormat()
+    return number
+
+
+def is_valid(number):
+    """Check if the number is a valid Hong Kong BR number."""
+    try:
+        return bool(validate(number))
+    except ValidationError:
+        return False
+
+
+def format(number):
+    """Reformat the number to the standard presentation format."""
+    return compact(number)

tests/test_hk_brn.doctest

@@ -0,0 +1,70 @@
+test_hk_brn.doctest - more detailed doctests for stdnum.hk.brn module
+
+Copyright (C) 2022 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
+
+
+This file contains more detailed doctests for the stdnum.hk.brn module. It
+tries to test more corner cases and detailed functionality that is not really
+useful as module documentation.
+
+>>> from stdnum.hk import brn
+
+
+Tests for some corner cases.
+
+>>> brn.validate('31130878')
+'31130878'
+>>> brn.validate('1767 4094')
+'17674094'
+>>> brn.format('1767 4094')
+'17674094'
+>>> brn.validate('12345')
+Traceback (most recent call last):
+    ...
+InvalidLength: ...
+>>> brn.validate('X2345678')
+Traceback (most recent call last):
+    ...
+InvalidFormat: ...
+
+
+These have been found online and should all be valid numbers.
+
+>>> numbers = '''
+...
+... 31130878
+... 52399423
+... 71623118
+... 33120398
+... 34647541
+... 58443527
+... 34214805
+... 12004664
+... 71536751
+... 1767 4094
+... 13603580
+... 34773491
+... 34395970
+... 33833767
+... 65556656
+... 15538767
+... 58650623
+...
+... '''
+>>> [x for x in numbers.splitlines() if x and not brn.is_valid(x)]
+[]