From 36662c92ff9055668f6f3665aaabf4b4bd0c9541 Mon Sep 17 00:00:00 2001
From: Agustin Scaramuzza <agustin@devsar.com>
Date: Mon, 18 Jan 2016 11:37:11 -0300
Subject: [PATCH] Add CBUField for Argentina

---
 docs/authors.rst        |  3 ++-
 localflavor/ar/forms.py | 59 +++++++++++++++++++++++++++++++++++++++++
 tests/test_ar.py        | 29 +++++++++++++++++++-
 3 files changed, 89 insertions(+), 2 deletions(-)

diff --git a/docs/authors.rst b/docs/authors.rst
index 2ec7ef2a0..c06d1d4ee 100644
--- a/docs/authors.rst
+++ b/docs/authors.rst
@@ -4,6 +4,7 @@ Authors
 * Aaron Boman
 * Adam Taylor
 * Adrian Holovaty
+* Agustín Scaramuzza
 * Alex Butum
 * Alex Gaynor
 * Alex Hill
@@ -63,4 +64,4 @@ Authors
 * d.merc
 * luyikei
 * tadeo
-* Łukasz Langa
+* Łukasz Langa
\ No newline at end of file
diff --git a/localflavor/ar/forms.py b/localflavor/ar/forms.py
index de418fbfb..0f096cad6 100644
--- a/localflavor/ar/forms.py
+++ b/localflavor/ar/forms.py
@@ -137,3 +137,62 @@ def _format(self, cuit, check_digit=None):
             check_digit = cuit[-1]
             cuit = cuit[:-1]
         return '%s-%s-%s' % (cuit[:2], cuit[2:], check_digit)
+
+
+class ARCBUField(CharField):
+    """
+    This field validates a CBU (Clave Bancaria Uniforme). A CBU is a 22-digits long
+    number. The first 8 digits denote bank and branch number, plus a verifying digit.
+    The remaining 14 digits denote an account number, plus a verifying digit.
+
+    More info:
+    http://www.clientebancario.gov.ar/default.asp
+    """
+    default_error_messages = {
+        'invalid': _('Enter a valid CBU in XXXXXXXXXXXXXXXXXXXXXX format.'),
+        'max_length': _('CBU must be exactly 22 digits long.'),
+        'min_length': _('CBU must be exactly 22 digits long.'),
+        'checksum': _("Invalid CBU."),
+    }
+
+    def __init__(self, *args, **kwargs):
+        kwargs['min_length'] = kwargs['max_length'] = 22
+        super(ARCBUField, self).__init__(*args, **kwargs)
+
+    def _valid_block(self, block, ponderator):
+        number = block[:-1]
+        v_digit = int(block[-1])
+
+        block_sum = sum(x * int(y) for x, y in zip(ponderator, number))
+        remainder = block_sum % 10
+
+        # The verification digit and the result of the calculation must be the same.
+        # In the edge case that the remainder is 0, the verification digit must be 0 too.
+        if remainder == 0:
+            return v_digit == remainder
+
+        return v_digit == (10 - remainder)
+
+    def _checksum(self, value):
+        block_1 = value[0:8]
+        block_2 = value[8:22]
+
+        PONDERATOR_1 = (9, 7, 1, 3, 9, 7, 1, 3)
+        PONDERATOR_2 = (3, 9, 7, 1, 3, 9, 7, 1, 3, 9, 7, 1, 3)
+
+        is_valid_1 = self._valid_block(block_1, PONDERATOR_1)
+        is_valid_2 = self._valid_block(block_2, PONDERATOR_2)
+        return is_valid_1 and is_valid_2
+
+    def clean(self, value):
+        """
+        Value must be a 22 digits long number.
+        """
+        value = super(ARCBUField, self).clean(value)
+        if value in EMPTY_VALUES:
+            return ''
+        if not value.isdigit():
+            raise ValidationError(self.error_messages['invalid'])
+        if not self._checksum(value):
+            raise ValidationError(self.error_messages['checksum'])
+        return value
diff --git a/tests/test_ar.py b/tests/test_ar.py
index 9f732de05..d7f8cd126 100644
--- a/tests/test_ar.py
+++ b/tests/test_ar.py
@@ -3,7 +3,7 @@
 from django.test import SimpleTestCase
 
 from localflavor.ar.forms import (ARProvinceSelect, ARPostalCodeField,
-                                  ARDNIField, ARCUITField)
+                                  ARDNIField, ARCUITField, ARCBUField)
 
 
 class ARLocalFlavorTests(SimpleTestCase):
@@ -104,3 +104,30 @@ def test_ARCUITField(self):
             '11211111110': error_legal_type,
         }
         self.assertFieldOutput(ARCUITField, valid, invalid)
+
+    def test_ARCBUField(self):
+        error_format = ['Enter a valid CBU in XXXXXXXXXXXXXXXXXXXXXX format.']
+        error_length = ['CBU must be exactly 22 digits long.']
+        error_checksum = ['Invalid CBU.']
+        valid = {
+            '2237628810898098715378': '2237628810898098715378',
+            '5433758936130717465023': '5433758936130717465023',
+            '5729195067928761667584': '5729195067928761667584',
+            '9498175528566296510521': '9498175528566296510521',
+            '7362966507842824472644': '7362966507842824472644',
+            '8693513393883886497274': '8693513393883886497274',
+            '1542952861593836535608': '1542952861593836535608',
+            '5833008953419074707467': '5833008953419074707467',
+            '9687027721961737239525': '9687027721961737239525',
+            '8048819274216931992586': '8048819274216931992586'
+        }
+
+        invalid = {
+            'abc123def456-9024-2313': error_format,
+            '142512591859898123123': error_length,
+            '12312452521512526125566': error_length,
+            '1234567891234567891234': error_checksum,
+            '1234562374545894589234': error_checksum,
+            '0987653759257883891234': error_checksum,
+        }
+        self.assertFieldOutput(ARCBUField, valid, invalid)