From f67b3fcac3c647e686aebd601ec2b7e1d47f6437 Mon Sep 17 00:00:00 2001
From: Benjamin Dauvergne <bdauvergne@entrouvert.com>
Date: Tue, 23 Jul 2019 17:40:14 +0200
Subject: [PATCH] template filter for Luhn algorithm (#35013)

---
 tests/test_templates.py           | 48 +++++++++++++++++++++++++++++
 wcs/qommon/templatetags/qommon.py | 50 +++++++++++++++++++++++++++++++
 2 files changed, 98 insertions(+)

diff --git a/tests/test_templates.py b/tests/test_templates.py
index 18f0ea65..38419746 100644
--- a/tests/test_templates.py
+++ b/tests/test_templates.py
@@ -522,3 +522,51 @@ def test_reproj():
     lazy_formdata = LazyFormData(MockFormData())
     tmpl = Template('{% with form_geoloc_base|reproj:"EPSG:3946" as c %}{{c.0}}/{{c.1}}{% endwith %}')
     assert tmpl.render(CompatibilityNamesDict({'form': lazy_formdata})) == '1625337.15483/5422836.71627'
+
+def test_luhn():
+    # Failing cases
+    tmpl = Template('{% if None|is_valid_siret%}yes{% endif %}')
+    assert tmpl.render() == ''
+    tmpl = Template('{% if True|is_valid_siret%}yes{% endif %}')
+    assert tmpl.render() == ''
+    tmpl = Template('{% if False|is_valid_siret%}yes{% endif %}')
+    assert tmpl.render() == ''
+
+    # EO Siret
+    tmpl = Template('{% if "44317013900036"|is_valid_siret%}yes{% endif %}')
+    assert tmpl.render() == 'yes'
+    tmpl = Template('{% if 44317013900036|is_valid_siret%}yes{% endif %}')
+    assert tmpl.render() == 'yes'
+
+    # with spaces
+    tmpl = Template('{% if  " 443 170\t139 00 036 "|is_valid_siret %}yes{% endif %}')
+    assert tmpl.render() == 'yes'
+    tmpl = Template('{{ " 443 170\t139 00 036 "|is_valid_siret }}')
+    assert tmpl.render() == '44317013900036'
+    for i in range(10):
+        if i == 6:
+            continue
+        tmpl = Template('{% if  "4431701390003' + str(i) + '"|is_valid_siret %}yes{% endif %}')
+        assert tmpl.render() == ''
+
+    # EO Siren
+    tmpl = Template('{% if  "443170139"|is_valid_siren %}yes{% endif %}')
+    assert tmpl.render() == 'yes'
+    for i in range(10):
+        if i == 9:
+            continue
+        tmpl = Template('{% if  "44317013' + str(i) + '"|is_valid_siren %}yes{% endif %}')
+        assert tmpl.render() == ''
+
+    # credit card number
+    tmpl = Template('{% if  "5555 5555 5555 4444"|is_valid_credit_card_number %}yes{% endif %}')
+    assert tmpl.render() == 'yes'
+    tmpl = Template('{{ "5555 5555 5555 4444"|is_valid_credit_card_number }}')
+    assert tmpl.render() == '5555555555554444'
+
+    # La poste
+    tmpl = Template('{% if  "356 000 000"|is_valid_siren%}yes{% endif %}')
+    assert tmpl.render() == 'yes'
+
+    tmpl = Template('{% if  "356 000 000 12345"|is_valid_siret%}yes{% endif %}')
+    assert tmpl.render() == 'yes'
diff --git a/wcs/qommon/templatetags/qommon.py b/wcs/qommon/templatetags/qommon.py
index 5178392d..6b96da93 100644
--- a/wcs/qommon/templatetags/qommon.py
+++ b/wcs/qommon/templatetags/qommon.py
@@ -20,6 +20,7 @@ from decimal import InvalidOperation as DecimalInvalidOperation
 from decimal import DivisionByZero as DecimalDivisionByZero
 import hashlib
 import math
+import re
 import string
 import random
 
@@ -348,3 +349,52 @@ def reproj(coords, projection_name):
     proj = pyproj.Proj(init='EPSG:4326')
     target_proj = pyproj.Proj(init=projection_name)
     return pyproj.transform(proj, target_proj, coords['lon'], coords['lat'])
+
+def clean_numeric_identifier(value):
+    if not value:
+        return u''
+    string_value = unicode(value)
+    string_value = re.sub(r'\s', '', string_value)
+    if not string_value.isdigit():
+        return u''
+    return string_value
+
+def is_valid_luhn(value, length=None):
+    '''Verify Luhn checksum on a string representing a number'''
+    if not value:
+        return u''
+    string_value = unicode(value)
+    if length is not None and len(string_value) != length:
+        return u''
+
+    # take all digits couting from the right, double value for digits pair
+    # index (counting from 1), if double has 2 digits take their sum
+    checksum = 0
+    for i, x in enumerate(reversed(string_value)):
+        if i % 2 == 0:
+            checksum += int(x)
+        else:
+            checksum += sum(int(y) for y in str(2 * int(x)))
+    if checksum % 10 != 0:
+        return u''
+    return string_value
+
+@register.filter
+def is_valid_siren(value):
+    string_value = clean_numeric_identifier(value)
+    # special case : La Poste
+    if string_value == '356000000':
+        return string_value
+    return is_valid_luhn(string_value, length=9)
+
+@register.filter
+def is_valid_siret(value):
+    string_value = clean_numeric_identifier(value)
+    # special case : La Poste
+    if string_value.startswith('356000000') and len(string_value) == 14:
+        return string_value
+    return is_valid_luhn(string_value, length=14)
+
+@register.filter
+def is_valid_credit_card_number(value):
+    return is_valid_luhn(clean_numeric_identifier(value), length=16)
-- 
2.22.0