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Shared/lib/python3.4/site-packages/stdnum/lv/pvn.py

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+# pvn.py - functions for handling Latvian PVN (VAT) numbers
+# coding: utf-8
+#
+# Copyright (C) 2012, 2013 Arthur de Jong
+#
+# 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
+
+"""PVN (Pievienotās vērtības nodokļa, Latvian VAT number).
+
+The PVN is a 11-digit number that can either be a reference to a legal
+entity (in which case the first digit > 3) or a natural person (in which
+case it should be the same as the personal code (personas kods)). Personal
+codes start with 6 digits to denote the birth date in the form ddmmyy.
+
+>>> validate('LV 4000 3521 600')
+'40003521600'
+>>> validate('40003521601')  # invalid check digit
+Traceback (most recent call last):
+    ...
+InvalidChecksum: ...
+>>> validate('161175-19997')  # personal code
+'16117519997'
+>>> validate('161375-19997')  # invalid date
+Traceback (most recent call last):
+    ...
+InvalidComponent: ...
+"""
+
+import datetime
+
+from stdnum.exceptions import *
+from stdnum.util import clean
+
+
+# validation functions are available on-line but it is not allowed
+# to perform automated queries:
+# http://www6.vid.gov.lv/VID_PDB?aspxerrorpath=/vid_pdb/pvn.asp
+
+
+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()
+    if number.startswith('LV'):
+        number = number[2:]
+    return number
+
+
+def checksum(number):
+    """Calculate the checksum for legal entities."""
+    weights = (9, 1, 4, 8, 3, 10, 2, 5, 7, 6, 1)
+    return sum(weights[i] * int(n) for i, n in enumerate(number)) % 11
+
+
+def calc_check_digit_pers(number):
+    """Calculate the check digit for personal codes. The number passed
+    should not have the check digit included."""
+    # note that this algorithm has not been confirmed by an independent source
+    weights = (10, 5, 8, 4, 2, 1, 6, 3, 7, 9)
+    check = 1 + sum(weights[i] * int(n) for i, n in enumerate(number))
+    return str(check % 11 % 10)
+
+
+def get_birth_date(number):
+    """Split the date parts from the number and return the birth date."""
+    day = int(number[0:2])
+    month = int(number[2:4])
+    year = int(number[4:6])
+    year += 1800 + int(number[6]) * 100
+    try:
+        return datetime.date(year, month, day)
+    except ValueError:
+        raise InvalidComponent()
+
+
+def validate(number):
+    """Checks to see if the number provided is a valid VAT number. This checks
+    the length, formatting and check digit."""
+    number = compact(number)
+    if not number.isdigit():
+        raise InvalidFormat()
+    if len(number) != 11:
+        raise InvalidLength()
+    if number[0] > '3':
+        # legal entity
+        if checksum(number) != 3:
+            raise InvalidChecksum()
+    else:
+        # natural resident, check if birth date is valid
+        birth_date = get_birth_date(number)
+        # TODO: check that the birth date is not in the future
+        if calc_check_digit_pers(number[:-1]) != number[-1]:
+            raise InvalidChecksum()
+    return number
+
+
+def is_valid(number):
+    """Checks to see if the number provided is a valid VAT number. This checks
+    the length, formatting and check digit."""
+    try:
+        return bool(validate(number))
+    except ValidationError:
+        return False