Fix #35 - implement Austria tax id number (#206)

idnumbers/nationalid/AUT.py

@@ -0,0 +1,67 @@
+import re
+from types import SimpleNamespace
+from .util import validate_regexp
+
+
+def normalize(id_number):
+    """strip out useless characters/whitespaces"""
+    return re.sub(r'[-/]', '', id_number)
+
+
+class TaxIDNumber:
+    """
+    Austria tax id number format
+    https://www.oecd.org/tax/automatic-exchange/crs-implementation-and-assistance/tax-identification-numbers/Austria-TIN.pdf
+    """
+    METADATA = SimpleNamespace(**{
+        'iso3166_alpha2': 'AT',
+        # length without insignificant chars
+        'min_length': 9,
+        'max_length': 9,
+        # has parse function
+        'parsable': False,
+        # has checksum function
+        'checksum': True,
+        # regular expression to validate the id
+        'regexp': re.compile(r'^(\d{2}-?\d{3}/?\d{4})$')
+    })
+
+    MULTIPLIER = [1, 2, 1, 2, 1, 2, 1, 2]
+    """The multiplier for checksum"""
+    OVERFLOW_SUM = {
+        10: 1,
+        12: 3,
+        14: 5,
+        16: 7,
+        18: 9
+    }
+    """checksum algorithm shows we have to sum the two digits if the weighted value > 9"""
+
+    @staticmethod
+    def validate(id_number: str) -> bool:
+        """
+        Validate the tax id number
+        """
+        if not validate_regexp(id_number, TaxIDNumber.METADATA.regexp):
+            return False
+        return TaxIDNumber.checksum(id_number)
+
+    @staticmethod
+    def checksum(id_number: str) -> bool:
+        if not validate_regexp(id_number, TaxIDNumber.METADATA.regexp):
+            return False
+        """algorithm: https://en.wikipedia.org/wiki/Tax_file_number#Check_digit"""
+        normalized = normalize(id_number)
+        numbers = [int(char) for char in list(normalized)]
+        total = 0
+        for (index, value) in enumerate(numbers[:-1]):
+            weighted = value * TaxIDNumber.MULTIPLIER[index]
+            if weighted in TaxIDNumber.OVERFLOW_SUM:
+                weighted = TaxIDNumber.OVERFLOW_SUM[weighted]
+            total += weighted
+        checksum = (100 - total) % 10
+        return checksum == numbers[-1]
+
+
+NationalID = TaxIDNumber
+"""alias of TaxIDNumber"""

tests/nationalid/test_AUT.py

@@ -0,0 +1,10 @@
+from unittest import TestCase
+from idnumbers.nationalid import AUT
+
+
+class TestAUTValidation(TestCase):
+    def test_normal_case(self):
+        self.assertTrue(AUT.TaxIDNumber.validate('931736581'))
+
+    def test_error_case(self):
+        self.assertFalse(AUT.TaxIDNumber.validate('931736580'))