==========================

Generic comment moderation

==========================

.. module:: django.contrib.comments.moderation

   :synopsis: Support for automatic comment moderation.

Django's bundled comments application is extremely useful on its own,

but the amount of comment spam circulating on the Web today

essentially makes it necessary to have some sort of automatic

moderation system in place for any application which makes use of

comments. To make this easier to handle in a consistent fashion,

``django.contrib.comments.moderation`` provides a generic, extensible

comment-moderation system which can be applied to any model or set of

models which want to make use of Django's comment system.

Overview

========

The entire system is contained within ``django.contrib.comments.moderation``,

and uses a two-step process to enable moderation for any given model:

1. A subclass of :class:`CommentModerator`

   is defined which specifies the moderation options the model wants to

   enable.

2. The model is registered with the moderation system, passing in the

   model class and the class which specifies its moderation options.

A simple example is the best illustration of this. Suppose we have the

following model, which would represent entries in a Weblog::

    from django.db import models

    class Entry(models.Model):

        title = models.CharField(maxlength=250)

        body = models.TextField()

        pub_date = models.DateTimeField()

        enable_comments = models.BooleanField()

Now, suppose that we want the following steps to be applied whenever a

new comment is posted on an ``Entry``:

1. If the ``Entry``'s ``enable_comments`` field is ``False``, the

   comment will simply be disallowed (i.e., immediately deleted).

2. If the ``enable_comments`` field is ``True``, the comment will be

   allowed to save.

3. Once the comment is saved, an email should be sent to site staff

   notifying them of the new comment.

Accomplishing this is fairly straightforward and requires very little

code::

    from django.contrib.comments.moderation import CommentModerator, moderator

    class EntryModerator(CommentModerator):

        email_notification = True

        enable_field = 'enable_comments'

    moderator.register(Entry, EntryModerator)

The :class:`CommentModerator` class pre-defines a number of useful moderation

options which subclasses can enable or disable as desired, and ``moderator``

knows how to work with them to determine whether to allow a comment, whether

to moderate a comment which will be allowed to post, and whether to email

notifications of new comments.

Built-in moderation options

---------------------------

.. class:: CommentModerator

    Most common comment-moderation needs can be handled by subclassing

    :class:`CommentModerator` and

    changing the values of pre-defined attributes; the full range of built-in

    options is as follows.

    .. attribute:: auto_close_field

        If this is set to the name of a

        :class:`~django.db.models.fields.DateField` or

        :class:`~django.db.models.fields.DateTimeField` on the model for which

        comments are being moderated, new comments for objects of that model

        will be disallowed (immediately deleted) when a certain number of days

        have passed after the date specified in that field. Must be

        used in conjunction with :attr:`close_after`, which specifies the

        number of days past which comments should be

        disallowed. Default value is ``None``.

    .. attribute:: auto_moderate_field

        Like :attr:`auto_close_field`, but instead of outright deleting

        new comments when the requisite number of days have elapsed,

        it will simply set the ``is_public`` field of new comments to

        ``False`` before saving them. Must be used in conjunction with

        :attr:`moderate_after`, which specifies the number of days past

        which comments should be moderated. Default value is ``None``.

    .. attribute:: close_after

        If :attr:`auto_close_field` is used, this must specify the number

        of days past the value of the field specified by

        :attr:`auto_close_field` after which new comments for an object

        should be disallowed. Default value is ``None``.

    .. attribute:: email_notification

        If ``True``, any new comment on an object of this model which

        survives moderation (i.e., is not deleted) will generate an

        email to site staff. Default value is ``False``.

    .. attribute:: enable_field

        If this is set to the name of a

        :class:`~django.db.models.fields.BooleanField` on the model

        for which comments are being moderated, new comments on

        objects of that model will be disallowed (immediately deleted)

        whenever the value of that field is ``False`` on the object

        the comment would be attached to. Default value is ``None``.

    .. attribute:: moderate_after

        If :attr:`auto_moderate_field` is used, this must specify the number

        of days past the value of the field specified by

        :attr:`auto_moderate_field` after which new comments for an object

        should be marked non-public. Default value is ``None``.

Simply subclassing :class:`CommentModerator` and changing the values of these

options will automatically enable the various moderation methods for any

models registered using the subclass.

Adding custom moderation methods

--------------------------------

For situations where the built-in options listed above are not

sufficient, subclasses of :class:`CommentModerator` can also override

the methods which actually perform the moderation, and apply any logic

they desire.  :class:`CommentModerator` defines three methods which

determine how moderation will take place; each method will be called

by the moderation system and passed two arguments: ``comment``, which

is the new comment being posted, ``content_object``, which is the

object the comment will be attached to, and ``request``, which is the

:class:`~django.http.HttpRequest` in which the comment is being submitted:

.. method:: CommentModerator.allow(comment, content_object, request)

    Should return ``True`` if the comment should be allowed to

    post on the content object, and ``False`` otherwise (in which

    case the comment will be immediately deleted).

.. method:: CommentModerator.email(comment, content_object, request)

    If email notification of the new comment should be sent to

    site staff or moderators, this method is responsible for

    sending the email.

.. method:: CommentModerator.moderate(comment, content_object, request)

    Should return ``True`` if the comment should be moderated (in

    which case its ``is_public`` field will be set to ``False``

    before saving), and ``False`` otherwise (in which case the

    ``is_public`` field will not be changed).

Registering models for moderation

---------------------------------

The moderation system, represented by

``django.contrib.comments.moderation.moderator`` is an instance of the class

:class:`Moderator`, which allows registration and "unregistration" of models

via two methods:

.. function:: moderator.register(model_or_iterable, moderation_class)

    Takes two arguments: the first should be either a model class

    or list of model classes, and the second should be a subclass

    of ``CommentModerator``, and register the model or models to

    be moderated using the options defined in the

    ``CommentModerator`` subclass. If any of the models are

    already registered for moderation, the exception

    :exc:`AlreadyModerated` will be raised.

.. function:: moderator.unregister(model_or_iterable)

    Takes one argument: a model class or list of model classes,

    and removes the model or models from the set of models which

    are being moderated. If any of the models are not currently

    being moderated, the exception

    :exc:`NotModerated` will be raised.

Customizing the moderation system

---------------------------------

Most use cases will work easily with simple subclassing of

:class:`CommentModerator` and registration with the provided

:class:`Moderator` instance, but customization of global moderation behavior

can be achieved by subclassing :class:`Moderator` and instead registering

models with an instance of the subclass.

.. class:: Moderator

    In addition to the :meth:`Moderator.register` and

    :meth:`Moderator.unregister` methods detailed above, the following methods

    on :class:`Moderator` can be overridden to achieve customized behavior:

    .. method:: connect

        Determines how moderation is set up globally. The base

        implementation in

        :class:`Moderator` does this by

        attaching listeners to the :data:`~django.contrib.comments.signals.comment_will_be_posted`

        and :data:`~django.contrib.comments.signals.comment_was_posted` signals from the

        comment models.

    .. method:: pre_save_moderation(sender, comment, request, **kwargs)

        In the base implementation, applies all pre-save moderation

        steps (such as determining whether the comment needs to be

        deleted, or whether it needs to be marked as non-public or

        generate an email).

    .. method:: post_save_moderation(sender, comment, request, **kwargs)

        In the base implementation, applies all post-save moderation

        steps (currently this consists entirely of deleting comments

        which were disallowed).