Add Indian virtual identity number

Closes #428

Author: deolekar

stdnum/in_/vid.py

@@ -0,0 +1,109 @@
+# vid.py - functions for handling Indian personal virtual identity numbers
+#
+# Copyright (C) 2024 Atul Deolekar
+#
+# 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
+
+"""VID (Indian personal virtual identity number).
+
+VID is a temporary, revocable 16-digit random number mapped with the Aadhaar number.
+VID is used in lieu of Aadhaar number whenever authentication or e-KYC services
+are performed.
+
+VID is made up of 16 digits where the last digits is a check digit
+calculated using the Verhoeff algorithm. The numbers are generated in a
+random, non-repeating sequence and do not begin with 0 or 1.
+
+More information:
+
+* https://uidai.gov.in/en/contact-support/have-any-question/284-faqs/aadhaar-online-services/virtual-id-vid.html
+* https://uidai.gov.in/images/resource/UIDAI_Circular_11012018.pdf
+
+>>> validate('2341234123412341')
+'2341234123412341'
+>>> validate('2341234123412342')
+Traceback (most recent call last):
+    ...
+InvalidChecksum: ...
+>>> validate('1341234123412341')  # number should not start with 0 or 1
+Traceback (most recent call last):
+    ...
+InvalidFormat: ...
+>>> validate('13412341234123')
+Traceback (most recent call last):
+    ...
+InvalidLength: ...
+>>> validate('2222222222222222')  # number cannot be a palindrome
+Traceback (most recent call last):
+    ...
+InvalidFormat: ...
+>>> format('2341234123412342')
+'2341 2341 2341 2342'
+>>> mask('2341234123412342')
+'XXXX XXXX  XXXX 2342'
+"""
+
+import re
+
+from stdnum import verhoeff
+from stdnum.exceptions import *
+from stdnum.util import clean
+
+
+_vid_re = re.compile(r'^[2-9][0-9]{15}$')
+"""Regular expression used to check syntax of VID numbers."""
+
+
+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, ' -').strip()
+
+
+def validate(number):
+    """Check if the number provided is a valid VID number. This checks
+    the length, formatting and check digit."""
+    number = compact(number)
+    if len(number) != 16:
+        raise InvalidLength()
+    if not _vid_re.match(number):
+        raise InvalidFormat()
+    if number == number[::-1]:
+        raise InvalidFormat()  # VID cannot be a palindrome
+    verhoeff.validate(number)
+    return number
+
+
+def is_valid(number):
+    """Check if the number provided is a valid VID number. This checks
+    the length, formatting and check digit."""
+    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[:4], number[4:8], number[8:12], number[12:]))
+
+
+def mask(number):
+    """Masks the first 8 digits as per Ministry of Electronics and
+    Information Technology (MeitY) guidelines."""
+    number = compact(number)
+    return 'XXXX XXXX XXXX ' + number[-4:]