incuna / incuna-groups

incuna-groups

An extensible Django app that provides forum functionality.

• Administrators can create discussion groups.
• Users can create discussions on groups, and comment on those discussions.
• Users can also subscribe to groups and/or discussions to receive notifications from them, and post responses by replying to the notification emails.

Installation

incuna-groups is on PyPI, so you can install it with pip install incuna-groups. Add both groups and pagination (for incuna-pagination, a dependency) to your INSTALLED_APPS.

This project contains migrations, so run python manage.py migrate before using it.

Usage

incuna-groups is self-contained - it provides models, views, and templates. At the moment, it doesn't provide styling or a REST API.

Some straightforward customisation is exposed through the AppConfig (which by default is groups.apps.GroupsConfig) and the templates can all be overridden easily.

Each page template has a base version that the page template itself directly extends, meaning you can replace the page template but still make use of all of the blocks and other HTML in the original. For instance, discussion_thread.html does nothing other than extend discussion_thread_base.html. You can override discussion_thread.html, extend discussion_thread_base.html in the same way, and change the content of, say, a single block, rather than having to copy and paste the entirety of the discussion thread template in and modify from there.

Models

There are three main models that everything revolves around, one of which is polymorphic for easy extension.

• Group: A group that contains any number of discussions, like a forum board. Created in the Django admin, and holds discussion threads added by users. A group can be denoted as private, in which case a user has to request to join it before they can read or post any comments. A group can also have moderators who have the ability to delete or edit other users' comments. Users can subscribe to a group, which will send them notifications for any discussions created on the group or comments posted to discussions in the group.
• Discussion: A single discussion thread, with at least one comment on it (the initial one). Created by a user. Users can comment on and subscribe to discussions. If a user is already subscribed to a discussion's parent group, they can "unsubscribe" from the discussion, which will (internally) cause the discussion to be 'ignored' for that user, and they won't get any notifications for it.
• BaseComment: A django-polymorphic base class for Comments. Doesn't do anything by itself, but is used for testing and to refer to arbitrary different kinds of comment. Subclasses of BaseComment are picked up by the discussion-related views. It comes with some subclasses:
  • TextComment: A comment with a text body - an entirely ordinary message.
  • FileComment: A comment containing an uploaded file.

Each of the three main models also has a custom queryset (which is then used by its manager) with several additional methods. Most of them allow fetching of recently active items or accessing groups/discussions/comments related to any instance of any of the three. These querysets and methods can be found in managers.py.

Views and admin pages

There are a lot of different views that come together to make the forums work.

• Group
  • Created by admin.GroupAdmin - in the Django admin
  • Listed by views.groups.GroupList
  • Detailed by views.groups.GroupDetail - implemented as a ListView for Discussions, to display the group's contents.
  • Subscribed to by views.subscriptions.GroupSubscribe
• Discussion
  • Created by admin.DiscussionAdmin - in the Django admin
  • Created by views.discussions.DiscussionCreate - this one also creates the Discussion's first comment, currently a TextComment.
  • Listed by views.groups.GroupDetail
  • Detailed by views.discussions.DiscussionThread - implemented as a CommentPostView from views._helpers, to allow people to reply via the discussion page itself.
  • Subscribed to by views.subscriptions.DiscussionSubscribe
• Comment
  • Created by views._helpers.CommentPostView - a base class that both creates comments and sends email notifications to relevant people.
  • Created by views.discussions.DiscussionThread - the discussion thread page provides an inline reply form that submits TextComments.
  • Created by views.comments.CommentUploadFile - a separate page for the uploading of FileComments.
  • Created by views.comments.CommentPostByEmail - an endpoint suitable for receiving email replies via Mailgun.
  • Listed by views.discussions.DiscussionThread
  • Deleted by views.comments.CommentDelete - a comment provides a 'delete' button which will archive it and hide its contents from view.

Notes on features

AppConfig

incuna-groups has an AppConfig, located in apps.py, which allows for easy customisation of some of its behaviour. The documentation on AppConfigs (and their use) is here: https://docs.djangoproject.com/en/1.8/ref/applications/#for-application-users

The AppConfig exposes:

• default_within_days - a default parameter for the within_days methods on some of the model managers, which return items that were posted or posted to within that time period.
• new_comment_subject and new_discussion_subject - subjects for notification emails. Each one will be formatted with the {discussion} a comment is on or the {group} a discussion belongs to, respectively.
• group_admin_class_path and discussion_admin_class_path - these allow you to override the admin behaviour of incuna-groups by slotting in alternate ModelAdmin classes. These may or may not be based on the existing admin classes in admin.py.

Email notifications

Whenever a discussion is created in a group, users subscribed to that group get an email notification. Whenever a comment is posted to a discussion, users subscribed to that discussion or its parent group also receive email notifications.

The email templates are in templates/groups/emails. Discussion notifications are sent by views.discussions.DiscussionCreate; comment notifications are sent by subclasses of CommentEmailMixin (CommentPostView, DiscussionThread and CommentUploadFile).

Email replies

Users can reply to discussions or comments by replying to the notification emails. Email replies are implemented by an endpoint (/groups/reply/, serving up the CommentPostByEmail view) that accepts POST requests containing JSON content representing the email. The library is set up to work with Mailgun routes.

The user and discussion are identified by a crafted Reply-To header, which contains a reply address of reply-{uuid}@{domain}. The UUID is generated by securely signing a dictionary of the user and discussion PKs, and unpacked by the endpoint when it receives Mailgun's JSON message. Mailgun provides a stripped-text field that removes quotes and signatures from the content of the email, so there's no need for users to reply in a specific way or for us to do any of that processing ourselves.

A rough API description for Mailgun can be found here. The POST and files data will be in request.POST and request.FILES respectively.

There are a couple of gotchas:

• The /groups/reply/ endpoint has a trailing slash. Ensure that this slash is included in any Mailgun route destination otherwise you'll get a stream of HTTP301s.
• If you're using incuna_auth.LoginRequiredMiddleware, make sure to add /groups/reply/ to LOGIN_EXEMPT_URLS to avoid more 301s.
• The CommentPostByEmail view has a @csrf_exempt decorator on the dispatch() method to avoid CSRF-related HTTP403 errors. If you extend the class, make sure to add the CSRF exemption.

Overriding admin classes

Group and Discussion both have custom admin classes, defined in admin.py. Both of these can be easily replaced by way of the AppConfig (see above). The AppConfig registers these admin classes for you, so don't call admin.site.register yourself.