From ef3db07d81099e0a10b330750fb39ec0e544b0d8 Mon Sep 17 00:00:00 2001
From: Benjamin Dauvergne <bdauvergne@entrouvert.com>
Date: Tue, 23 Jul 2019 17:40:14 +0200
Subject: [PATCH] fields: add Luhn algorithm to string field validation
 (#35013)

---
 tests/test_widgets.py | 38 ++++++++++++++++++++++++++++++++++++++
 wcs/qommon/form.py    |  5 +++++
 wcs/qommon/misc.py    | 33 +++++++++++++++++++++++++++++++++
 3 files changed, 76 insertions(+)

diff --git a/tests/test_widgets.py b/tests/test_widgets.py
index d1481182..03ad0ccd 100644
--- a/tests/test_widgets.py
+++ b/tests/test_widgets.py
@@ -630,6 +630,44 @@ def test_wcsextrastringwidget_builtin_validation():
     mock_form_submission(req, widget, {'test': '1234'})
     assert widget.has_error()
 
+def test_wcsextrastringwidget_siren_validation():
+    class FakeField: pass
+    fakefield = FakeField()
+    fakefield.validation = {'type': 'siren-fr'}
+
+    widget = WcsExtraStringWidget('test', value='foo', required=False)
+    widget.field = fakefield
+    mock_form_submission(req, widget, {'test': '443170139'})
+    assert not widget.has_error()
+
+    widget = WcsExtraStringWidget('test', value='foo', required=False)
+    widget.field = fakefield
+    mock_form_submission(req, widget, {'test': '443170130'})
+    assert widget.has_error()
+
+def test_wcsextrastringwidget_siret_validation():
+    class FakeField: pass
+    fakefield = FakeField()
+    fakefield.validation = {'type': 'siret-fr'}
+
+    # regular case
+    widget = WcsExtraStringWidget('test', value='foo', required=False)
+    widget.field = fakefield
+    mock_form_submission(req, widget, {'test': '44317013900036'})
+    assert not widget.has_error()
+
+    # special case la poste
+    widget = WcsExtraStringWidget('test', value='foo', required=False)
+    widget.field = fakefield
+    mock_form_submission(req, widget, {'test': '35600000000048'})
+    assert not widget.has_error()
+
+    # failing case
+    widget = WcsExtraStringWidget('test', value='foo', required=False)
+    widget.field = fakefield
+    mock_form_submission(req, widget, {'test': '44317013900037'})
+    assert widget.has_error()
+
 def test_wcsextrastringwidget_django_validation():
     class FakeField: pass
     fakefield = FakeField()
diff --git a/wcs/qommon/form.py b/wcs/qommon/form.py
index 2a7702f9..86021aa5 100644
--- a/wcs/qommon/form.py
+++ b/wcs/qommon/form.py
@@ -906,6 +906,8 @@ class ValidationWidget(CompositeWidget):
         ('digits', {'title': N_('Digits'), 'regex': '\d+'}),
         ('phone-fr', {'title': N_('Phone Number (France)'), 'regex': '0[\d\.\s]{9}'}),
         ('zipcode-fr', {'title': N_('Zip Code (France)'), 'regex': '\d{5}'}),
+        ('siren-fr', {'title': N_('SIREN Code (France)'), 'function': 'validate_siren'}),
+        ('siret-fr', {'title': N_('SIRET Code (France)'), 'function': 'validate_siret'}),
         ('regex', {'title': N_('Regular Expression')}),
         ('django', {'title': N_('Django Condition')}),
     ])
@@ -965,6 +967,9 @@ class ValidationWidget(CompositeWidget):
                 condition = ValidationCondition(validation['value'], value=value)
                 return condition.evaluate()
             return django_validation
+        validation_method = cls.validation_methods.get(validation['type'])
+        if 'function' in validation_method:
+            return getattr(misc, validation_method['function'])
 
     @classmethod
     def get_validation_pattern(cls, validation):
diff --git a/wcs/qommon/misc.py b/wcs/qommon/misc.py
index 3a441bf2..3c4bcf7d 100644
--- a/wcs/qommon/misc.py
+++ b/wcs/qommon/misc.py
@@ -639,3 +639,36 @@ def html2text(text):
     if isinstance(text, (htmltext, str)):
         text = unicode(str(text), get_publisher().site_charset)
     return site_encode(HTMLParser().unescape(strip_tags(text)))
+
+
+def validate_luhn(string_value, length=None):
+    '''Verify Luhn checksum on a string representing a number'''
+    if not string_value:
+        return False
+    if length is not None and len(string_value) != length:
+        return False
+
+    # take all digits counting 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 False
+    return True
+
+
+def validate_siren(string_value):
+    return validate_luhn(string_value, length=9)
+
+
+def validate_siret(string_value):
+    # special case : La Poste
+    if (string_value.startswith('356000000')
+            and len(string_value) == 14
+            and sum(int(x) for x in string_value) % 5 == 0):
+        return True
+    return validate_luhn(string_value, length=14)
-- 
2.23.0.rc1