django-tos: A Python repository from karbassi

django-tos

This project gives the admin the ability to reset terms of agreement with the end users. It tracks when TOS are changed and when users agree to the new TOS.

Summary

Keeps track of when TOS is changed
Users need to be informed and agree/re-agree when they login (custom login is provided)
Just two models (TOS and user agreement)

Terms Of Service Installation

pip install django-tos
Add tos to your INSTALLED_APPS setting.
Sync your database with python manage.py migrate or python manage.py syncdb for Django < 1.7.

Configuration

Options

There are two ways to configure django-tos - either enable the TOS check when users sign in, or use middleware to enable the TOS check on every GET request.

If you cannot override your login view (for instance, if you're using django-allauth) you should use the second option.

Option 1: TOS Check On Sign In

In your root urlconf file urls.py add:

from tos.views import login

# terms of service links
urlpatterns += patterns('',
    url(r'^login/$', login, {}, 'auth_login',),
    url(r'^terms-of-service/', include('tos.urls')),
)

Option 2: Middleware Check

This option uses the incr methods for the configured Django cache. If you are using django-tos in a complex or parallel environment, be sure to use a cache backend that supports atomic increment operations. For more information, see the notes at the end of this section of the Django documentation.

Also, to ensure that warming the cache with users who can skip the agreement check works properly, you will need to include tos before your app (myapp in the example) in your INSTALLED_APPS setting:

INSTALLED_APPS = (
    ...
    'tos',
    ...
    'myapp',  # Example app name
    ...
)

Advantages

Can optionally use a separate cache for TOS agreements (necessary if your default cache does not support atomic increment operations)
Allow some of your users to skip the TOS check (eg: developers, staff, admin, superusers, employees)
Uses signals to invalidate cached agreements
Skips the agreement check when the user is anonymous or not signed in
Skips the agreement check when the request is AJAX
Skips the agreement check when the request isn't a GET request (to avoid getting in the way of data mutations)

Disadvantages

Requires a cache key for each user who is signed in
Requires an additional cache key for each staff user
May leave keys in the cache when the active TermsOfService changes

Efficiency

Best case for staff users: 2 cache hits
Best case for non-staff users: 1 cache miss, 2 cache hits
Worst case: 1 cache hit, 2 cache misses, 1 database query, 1 cache set (this should only happen when the user signs in)

Option 2 Configuration

In your root urlconf file urls.py only add the terms-of-service URLs:

# terms of service links
urlpatterns += patterns('',
    url(r'^terms-of-service/', include('tos.urls')),
)

Optional: Since the cache used by TOS will be overwhelmingly read-heavy, you can use a separate cache specifically for TOS. To do so, create a new cache in your project's settings.py:

CACHES = {
    ...
    # The cache specifically for django-tos
    'tos': {  # Can use any name here
        'BACKEND': ...,
        'LOCATION': ...,
        'NAME': 'tos-cache',  # Can use any name here
    },
}

and configure django-tos to use the new cache:

TOS_CACHE_NAME = 'tos'  # Must match the key name in in CACHES

this setting defaults to the default cache.

Then in your project's settings.py add the middleware to MIDDLEWARE_CLASSES:

MIDDLEWARE_CLASSES = (
    ...
    # Terms of service checks
    'tos.middleware.UserAgreementMiddleware',
)

Optional: To allow users to skip the TOS check, you will need to set corresponding cache keys for them in the TOS cache. The cache key for each user will need to be prefixed with django:tos:skip_tos_check:, and have the user ID appended to it.

Here is an example app configuration that allows staff users and superusers to skip the TOS agreement check:

from django.apps import AppConfig, apps
from django.conf import settings
from django.contrib.auth import get_user_model
from django.core.cache import caches
from django.db.models import Q
from django.db.models.signals import post_save, pre_save
from django.dispatch import receiver

class MyAppConfig(AppConfig):
    name = 'myapp'

    def ready(self):
        if 'tos' in settings.INSTALLED_APPS:
            cache = caches[getattr(settings, 'TOS_CACHE_NAME', 'default')]
            tos_app = apps.get_app_config('tos')
            TermsOfService = tos_app.get_model('TermsOfService')

            @receiver(post_save, sender=get_user_model(), dispatch_uid='set_staff_in_cache_for_tos')
            def set_staff_in_cache_for_tos(user, instance, **kwargs):
                if kwargs.get('raw', False):
                    return

                # Get the cache prefix
                key_version = cache.get('django:tos:key_version')

                # If the user is staff allow them to skip the TOS agreement check
                if instance.is_staff or instance.is_superuser:
                    cache.set('django:tos:skip_tos_check:{}'.format(instance.id), version=key_version)

                # But if they aren't make sure we invalidate them from the cache
                elif cache.get('django:tos:skip_tos_check:{}'.format(instance.id), False):
                    cache.delete('django:tos:skip_tos_check:{}'.format(instance.id), version=key_version)

            @receiver(post_save, sender=TermsOfService, dispatch_uid='add_staff_users_to_tos_cache')
            def add_staff_users_to_tos_cache(*args, **kwargs):
                if kwargs.get('raw', False):
                    return

                # Get the cache prefix
                key_version = cache.get('django:tos:key_version')

                # Efficiently cache all of the users who are allowed to skip the TOS
                # agreement check
                cache.set_many({
                    'django:tos:skip_tos_check:{}'.format(staff_user.id): True
                    for staff_user in get_user_model().objects.filter(
                        Q(is_staff=True) | Q(is_superuser=True))
                }, version=key_version)

            # Immediately add staff users to the cache
            add_staff_users_to_tos_cache()

django-tos-i18n

django-tos internationalization using django-modeltranslation.

Terms Of Service i18n Installation

Assuming you have correctly installed django-tos in your app you only need to add following apps to INSTALLED_APPS:

INSTALLED_APPS += ('modeltranslation', 'tos_i18n')

and also you should also define your languages in Django LANGUAGES variable, e.g.:

LANGUAGES = (
    ('pl', 'Polski'),
    ('en', 'English'),
)

Please note that adding those to INSTALLED_APPS changes Django models. Concretely it adds for every registered field that should translated, additional fields with name field_<lang_code>, e.g. for given model:

class MyModel(models.Model):
    name = models.CharField(max_length=10)

There will be generated fields: name , name_en, name_pl.

You should probably migrate your database, and if you're using Django < 1.7 using South is recommended. These migrations should be kept in your local project.

How to migrate tos with South

Here is some step-by-step example how to convert your legacy django-tos instalation synced using syncdb into a translated django-tos-i18n with South migrations.

Inform South that you want to store migrations in custom place by putting this in your Django settings file:
```
SOUTH_MIGRATION_MODULES = {
    'tos': 'YOUR_APP.migrations.tos',
}
```

Add required directory (package):

mkdir -p YOUR_APP/migrations/tos
touch YOUR_APP/migrations/tos/__init__.py

Create initial migration (referring to the database state as it is now):
```
python manage.py schemamigration --initial tos
```
Fake migration (because the changes are already in the database):
```
python manage.py migrate tos --fake
```
Install tos_i18n (and modeltranslation) to INSTALLED_APPS:
```
INSTALLED_APPS += ('modeltranslation', 'tos_i18n',)
```
Make sure that the Django LANGUAGES setting is properly configured.

Migrate what changed:

$ python manage.py schemamigration --auto tos
$ python migrate tos

That's it. You are now running tos in i18n mode with the languages you declared in LANGUAGES setting. This will also make all required adjustments in the Django admin.

For more info on how translation works in details please refer to the django-modeltranslation documentation.

karbassi/django-tos