Implemented seperate EAN validators

To be used in Swiss SSN implementation

localflavor/generic/checksums.py

@@ -3,9 +3,10 @@
 """
 from django.utils import six
 
-__all__ = ['luhn']
+__all__ = ['luhn', 'ean']
 
 LUHN_ODD_LOOKUP = (0, 2, 4, 6, 8, 1, 3, 5, 7, 9)  # sum_of_digits(index * 2)
+EAN_LOOKUP = (3, 1)
 
 
 def luhn(candidate):
@@ -22,3 +23,24 @@ def luhn(candidate):
         return ((evens + odds) % 10 == 0)
     except ValueError:  # Raised if an int conversion fails
         return False
+
+
+def ean(candidate):
+    """
+    Checks a candidate number for validity according to the EAN checksum calculation.
+    Note that this validator does not enforce any length checks (usually 13 or 8).
+
+    http://en.wikipedia.org/wiki/International_Article_Number_(EAN)
+    """
+    if not isinstance(candidate, six.string_types):
+        candidate = str(candidate)
+    if len(candidate) <= 1:
+        return False
+    given_number, given_checksum = candidate[:-1], candidate[-1]
+    try:
+        calculated_checksum = sum(
+            int(digit) * EAN_LOOKUP[i % 2] for i, digit in enumerate(reversed(given_number)))
+        calculated_checksum = 10 - (calculated_checksum % 10)
+        return str(calculated_checksum) == given_checksum
+    except ValueError:  # Raised if an int conversion fails
+        return False

localflavor/generic/validators.py

@@ -1,11 +1,15 @@
 # -*- coding: utf-8 -*-
 from __future__ import unicode_literals
 
+import re
+
 import string
 
 from django.core.exceptions import ValidationError, ImproperlyConfigured
 from django.utils.translation import ugettext_lazy as _
+
 from .countries.iso_3166 import ISO_3166_1_ALPHA2_COUNTRY_CODES
+from . import checksums
 
 # Dictionary of ISO country code to IBAN length.
 #
@@ -20,6 +24,7 @@
 # http://www.ecbs.org/iban/france-bank-account-number.html
 # https://www.nordea.com/V%C3%A5ra+tj%C3%A4nster/Internationella+produkter+och+tj%C3%A4nster/Cash+Management/IBAN+countries/908472.html
 
+
 IBAN_COUNTRY_CODE_LENGTH = {'AL': 28,  # Albania
                             'AD': 24,  # Andorra
                             'AE': 23,  # United Arab Emirates
@@ -209,3 +214,25 @@ def __call__(self, value):
         country_code = value[4:6]
         if country_code not in ISO_3166_1_ALPHA2_COUNTRY_CODES:
             raise ValidationError(_('%s is not a valid country code.') % country_code)
+
+
+class EANValidator(object):
+    """
+    A generic validator for EAN like codes with the last digit being the checksum.
+
+    http://en.wikipedia.org/wiki/International_Article_Number_(EAN)
+    """
+    message = _('Not a valid EAN code.')
+
+    def __init__(self, strip_nondigits=False, message=None):
+        if message is not None:
+            self.message = message
+        self.strip_nondigits = strip_nondigits
+
+    def __call__(self, value):
+        if value is None:
+            return value
+        if self.strip_nondigits:
+            value = re.compile(r'[^\d]+').sub('', value)
+        if not checksums.ean(value):
+            raise ValidationError(self.message)

tests/test_checksums.py

@@ -5,11 +5,16 @@
 
 class TestUtilsChecksums(unittest.TestCase):
 
+    def assertChecksumOuput(self, checksum, result_pairs):
+        for value, output in result_pairs:
+            self.assertEqual(checksum(value), output, "Expected %s(%s) == %s but got %s" % (
+                checksum.__name__, repr(value), output, not output))
+
     def test_luhn(self):
         """
         Check that function(value) equals output.
         """
-        items = (
+        result_pairs = (
             (4111111111111111, True),
             ('4111111111111111', True),
             (4222222222222, True),
@@ -30,5 +35,18 @@ def test_luhn(self):
             (None, False),
             (object(), False),
         )
-        for value, output in items:
-            self.assertEqual(checksums.luhn(value), output, value)
+        self.assertChecksumOuput(checksums.luhn, result_pairs)
+
+    def test_ean(self):
+        result_pairs = (
+            ('73513537', True),
+            (73513537, True),
+            ('73513538', False),
+            (73513538, False),
+            ('4006381333931', True),
+            (4006381333931, True),
+            ('abc', False),
+            (None, False),
+            (object(), False),
+        )
+        self.assertChecksumOuput(checksums.ean, result_pairs)

tests/test_generic.py

@@ -7,7 +7,7 @@
 
 from localflavor.generic.countries.sepa import IBAN_SEPA_COUNTRIES
 from localflavor.generic.models import BICField, IBANField
-from localflavor.generic.validators import BICValidator, IBANValidator
+from localflavor.generic.validators import BICValidator, IBANValidator, EANValidator
 from localflavor.generic.forms import DateField, DateTimeField, SplitDateTimeField, BICFormField, IBANFormField
 
 
@@ -337,3 +337,63 @@ def test_bic_model_field(self):
     def test_default_form(self):
         bic_model_field = BICField()
         self.assertEqual(type(bic_model_field.formfield()), type(BICFormField()))
+
+
+class EANTests(TestCase):
+
+    def test_ean_validator(self):
+        valid = [
+            '4006381333931',
+            '73513537',
+
+            '012345678905',
+            '0012345678905',
+
+            None,
+        ]
+        error_message = 'Not a valid EAN code.'
+        invalid = [
+            '400.6381.3339.31',
+            '4006381333930',
+            '',
+            '0',
+            'DÉUTDEFF',
+        ]
+
+        validator = EANValidator()
+        for value in valid:
+            validator(value)
+
+        for value in invalid:
+            self.assertRaisesMessage(ValidationError,  error_message, validator, value)
+
+    def test_ean_validator_strip_nondigits(self):
+        valid = [
+            '4006381333931',
+            '400.6381.3339.31',
+            '73513537',
+            '73-51-3537',
+            '73 51 3537',
+            '73A51B3537',
+
+            '012345678905',
+            '0012345678905',
+
+            None,
+        ]
+        error_message = 'Not a valid EAN code.'
+        invalid = [
+            '4006381333930',
+            '400-63-813-339-30',
+            '400 63 813 339 30',
+            '',
+            '0',
+            'DÉUTDEFF',
+        ]
+
+        validator = EANValidator(strip_nondigits=True)
+        for value in valid:
+            validator(value)
+
+        for value in invalid:
+            self.assertRaisesMessage(ValidationError,  error_message, validator, value)