/askbot/models/content.py

import datetime
from django.contrib.auth.models import User
from django.contrib.contenttypes import generic
from django.contrib.contenttypes.models import ContentType
from django.db import models
from django.utils import html as html_utils
from django.utils.datastructures import SortedDict
from askbot import const
from askbot.models.meta import Comment, Vote
from askbot.models.user import EmailFeedSetting
from askbot.models.tag import Tag, MarkedTag, tags_match_some_wildcard
from askbot.conf import settings as askbot_settings

class Content(models.Model):
    """
        Base class for Question and Answer
    """
    author = models.ForeignKey(User, related_name='%(class)ss')
    added_at = models.DateTimeField(default=datetime.datetime.now)

    wiki = models.BooleanField(default=False)
    wikified_at = models.DateTimeField(null=True, blank=True)

    locked = models.BooleanField(default=False)
    locked_by = models.ForeignKey(User, null=True, blank=True, related_name='locked_%(class)ss')
    locked_at = models.DateTimeField(null=True, blank=True)

    score = models.IntegerField(default=0)
    vote_up_count = models.IntegerField(default=0)
    vote_down_count = models.IntegerField(default=0)

    comment_count = models.PositiveIntegerField(default=0)
    offensive_flag_count = models.SmallIntegerField(default=0)

    last_edited_at = models.DateTimeField(null=True, blank=True)
    last_edited_by = models.ForeignKey(User, null=True, blank=True, related_name='last_edited_%(class)ss')

    html = models.TextField(null=True)#html rendition of the latest revision
    text = models.TextField(null=True)#denormalized copy of latest revision
    comments = generic.GenericRelation(Comment)
    votes = generic.GenericRelation(Vote)

    _use_markdown = True
    _escape_html = False #markdow does the escaping
    _urlize = False

    class Meta:
        abstract = True
        app_label = 'askbot'

    def get_comments(self, visitor = None):
        """returns comments for a post, annotated with
        ``upvoted_by_user`` parameter, if visitor is logged in
        otherwise, returns query set for all comments to a given post
        """
        if visitor.is_anonymous():
            return self.comments.all().order_by('id')
        else:
            comment_content_type = ContentType.objects.get_for_model(Comment)
            #a fancy query to annotate comments with the visitor votes
            comments = self.comments.extra(
                select = SortedDict([
                            (
                                'upvoted_by_user',
                                'SELECT COUNT(*) from vote, comment '
                                'WHERE vote.user_id = %s AND '
                                'vote.content_type_id = %s AND '
                                'vote.object_id = comment.id',
                            )
                        ]),
                select_params = (visitor.id, comment_content_type.id)
            ).order_by('id')
            return comments

    #todo: maybe remove this wnen post models are unified
    def get_text(self):
        return self.text

    def get_snippet(self):
        """returns an abbreviated snippet of the content
        """
        return html_utils.strip_tags(self.html)[:120] + ' ...'

    def add_comment(self, comment=None, user=None, added_at=None):
        if added_at is None:
            added_at = datetime.datetime.now()
        if None in (comment ,user):
            raise Exception('arguments comment and user are required')

        #Comment = models.get_model('askbot','Comment')#todo: forum hardcoded
        comment = Comment(
                            content_object=self, 
                            comment=comment, 
                            user=user, 
                            added_at=added_at
                        )
        comment.parse_and_save(author = user)
        self.comment_count = self.comment_count + 1
        self.save()

        #tried to add this to bump updated question
        #in most active list, but it did not work
        #becase delayed email updates would be triggered
        #for cases where user did not subscribe for them
        #
        #need to redo the delayed alert sender
        #
        #origin_post = self.get_origin_post()
        #if origin_post == self:
        #    self.last_activity_at = added_at
        #    self.last_activity_by = user
        #else:
        #    origin_post.last_activity_at = added_at
        #    origin_post.last_activity_by = user
        #    origin_post.save()

        return comment

    def get_global_tag_based_subscribers(
                                    self,
                                    tag_mark_reason = None,
                                    subscription_records = None
                                ):
        """returns a list of users who either follow or "do not ignore"
        the given set of tags, depending on the tag_mark_reason

        ``subscription_records`` - query set of ``~askbot.models.EmailFeedSetting``
        this argument is used to reduce number of database queries
        """
        if tag_mark_reason == 'good':
            email_tag_filter_strategy = const.INCLUDE_INTERESTING
            user_set_getter = User.objects.filter
        elif tag_mark_reason == 'bad':
            email_tag_filter_strategy = const.EXCLUDE_IGNORED
            user_set_getter = User.objects.exclude
        else:
            raise ValueError('Uknown value of tag mark reason %s' % tag_mark_reason)

        #part 1 - find users who follow or not ignore the set of tags
        tag_names = self.get_tag_names()
        tag_selections = MarkedTag.objects.filter(
                                            tag__name__in = tag_names,
                                            reason = tag_mark_reason
                                        )
        subscribers = set(
            user_set_getter(
                tag_selections__in = tag_selections
            ).filter(
                notification_subscriptions__in = subscription_records
            ).filter(
                email_tag_filter_strategy = email_tag_filter_strategy
            )
        )

        #part 2 - find users who follow or not ignore tags via wildcard selections
        #inside there is a potentially time consuming loop
        if askbot_settings.USE_WILDCARD_TAGS:
            #todo: fix this 
            #this branch will not scale well
            #because we have to loop through the list of users
            #in python
            if tag_mark_reason == 'good':
                empty_wildcard_filter = {'interesting_tags__exact': ''}
                wildcard_tags_attribute = 'interesting_tags'
                update_subscribers = lambda the_set, item: the_set.add(item)
            elif tag_mark_reason == 'bad':
                empty_wildcard_filter = {'ignored_tags__exact': ''}
                wildcard_tags_attribute = 'ignored_tags'
                update_subscribers = lambda the_set, item: the_set.discard(item)

            potential_wildcard_subscribers = User.objects.filter(
                notification_subscriptions__in = subscription_records
            ).filter(
                email_tag_filter_strategy = email_tag_filter_strategy
            ).exclude(
                **empty_wildcard_filter #need this to limit size of the loop
            )
            for potential_subscriber in potential_wildcard_subscribers:
                wildcard_tags = getattr(
                                    potential_subscriber,
                                    wildcard_tags_attribute
                                ).split(' ')

                if tags_match_some_wildcard(tag_names, wildcard_tags):
                    update_subscribers(subscribers, potential_subscriber)

        return subscribers

    def get_global_instant_notification_subscribers(self):
        """returns a set of subscribers to post according to tag filters
        both - subscribers who ignore tags or who follow only
        specific tags

        this method in turn calls several more specialized
        subscriber retrieval functions
        todo: retrieval of wildcard tag followers ignorers
              won't scale at all
        """
        subscriber_set = set()

        global_subscriptions = EmailFeedSetting.objects.filter(
                                                    feed_type = 'q_all',
                                                    frequency = 'i'
                                                )

        #segment of users who have tag filter turned off
        global_subscribers = User.objects.filter(
            email_tag_filter_strategy = const.INCLUDE_ALL
        )
        subscriber_set.update(global_subscribers)

        #segment of users who want emails on selected questions only
        subscriber_set.update(
            self.get_global_tag_based_subscribers(
                                        subscription_records = global_subscriptions,
                                        tag_mark_reason = 'good'
                                    )
        )

        #segment of users who want to exclude ignored tags
        subscriber_set.update(
            self.get_global_tag_based_subscribers(
                                        subscription_records = global_subscriptions,
                                        tag_mark_reason = 'bad'
                                    )
        )
        return subscriber_set


    def get_instant_notification_subscribers(
                                self,
                                potential_subscribers = None,
                                mentioned_users = None,
                                exclude_list = None,
                            ):
        """get list of users who have subscribed to
        receive instant notifications for a given post
        this method works for questions and answers

        Arguments:

        * ``potential_subscribers`` is not used here! todo: why? - clean this out
          parameter is left for the uniformity of the interface
          (Comment method does use it)
          normally these methods would determine the list
          :meth:`~askbot.models.question.Question.get_response_recipients`
          :meth:`~askbot.models.question.Answer.get_response_recipients`
          - depending on the type of the post
        * ``mentioned_users`` - users, mentioned in the post for the first time
        * ``exclude_list`` - users who must be excluded from the subscription

        Users who receive notifications are:

        * of ``mentioned_users`` - those who subscribe for the instant
          updates on the @name mentions
        * those who follow the parent question
        * global subscribers (any personalized tag filters are applied)
        * author of the question who subscribe to instant updates 
          on questions that they asked
        * authors or any answers who subsribe to instant updates
          on the questions which they answered
        """
        #print '------------------'
        #print 'in content function'
        subscriber_set = set()
        #print 'potential subscribers: ', potential_subscribers

        #1) mention subscribers - common to questions and answers
        if mentioned_users:
            mention_subscribers = EmailFeedSetting.objects.filter_subscribers(
                                            potential_subscribers = mentioned_users,
                                            feed_type = 'm_and_c',
                                            frequency = 'i'
                                        )
            subscriber_set.update(mention_subscribers)

        origin_post = self.get_origin_post()

        #print origin_post

        #2) individually selected - make sure that users
        #are individual subscribers to this question
        selective_subscribers = origin_post.followed_by.all()
        #print 'question followers are ', [s for s in selective_subscribers]
        if selective_subscribers:
            selective_subscribers = EmailFeedSetting.objects.filter_subscribers(
                                potential_subscribers = selective_subscribers,
                                feed_type = 'q_sel',
                                frequency = 'i'
                            )
            subscriber_set.update(selective_subscribers)
            #print 'selective subscribers: ', selective_subscribers

        #3) whole forum subscribers
        global_subscribers = origin_post.get_global_instant_notification_subscribers()
        subscriber_set.update(global_subscribers)

        #4) question asked by me (todo: not "edited_by_me" ???)
        question_author = origin_post.author
        if EmailFeedSetting.objects.filter(
                                            subscriber = question_author,
                                            frequency = 'i',
                                            feed_type = 'q_ask'
                                        ):
            subscriber_set.add(question_author)

        #4) questions answered by me -make sure is that people 
        #are authors of the answers to this question
        #todo: replace this with a query set method
        answer_authors = set()
        for answer in origin_post.answers.all():
            authors = answer.get_author_list()
            answer_authors.update(authors)

        if answer_authors:
            answer_subscribers = EmailFeedSetting.objects.filter_subscribers(
                                    potential_subscribers = answer_authors,
                                    frequency = 'i',
                                    feed_type = 'q_ans',
                                )
            subscriber_set.update(answer_subscribers)
            #print 'answer subscribers: ', answer_subscribers

        #print 'exclude_list is ', exclude_list
        subscriber_set -= set(exclude_list)

        #print 'final subscriber set is ', subscriber_set
        return list(subscriber_set)

    def get_latest_revision(self):
        return self.revisions.all().order_by('-revised_at')[0]

    def get_latest_revision_number(self):
        return self.get_latest_revision().revision

    def get_time_of_last_edit(self):
        if self.last_edited_at:
            return self.last_edited_at
        else:
            return self.added_at

    def get_owner(self):
        return self.author

    def get_author_list(
                    self,
                    include_comments = False, 
                    recursive = False, 
                    exclude_list = None):

        #todo: there may be a better way to do these queries
        authors = set()
        authors.update([r.author for r in self.revisions.all()])
        if include_comments:
            authors.update([c.user for c in self.comments.all()])
        if recursive:
            if hasattr(self, 'answers'):
                for a in self.answers.exclude(deleted = True):
                    authors.update(a.get_author_list( include_comments = include_comments ) )
        if exclude_list:
            authors -= set(exclude_list)
        return list(authors)

    def passes_tag_filter_for_user(self, user):

        question = self.get_origin_post()
        if user.email_tag_filter_strategy == const.INCLUDE_INTERESTING:
            #at least some of the tags must be marked interesting
            return user.has_affinity_to_question(
                                            question,
                                            affinity_type = 'like'
                                        )
        elif user.email_tag_filter_strategy == const.EXCLUDE_IGNORED:
            return not user.has_affinity_to_question(
                                            question,
                                            affinity_type = 'dislike'
                                        )
        elif user.email_tag_filter_strategy == const.INCLUDE_ALL:
            return True
        else:
            raise ValueError(
                        'unexpected User.email_tag_filter_strategy %s' \
                        % user.email_tag_filter_strategy
                    )

    def post_get_last_update_info(self):#todo: rename this subroutine
        when = self.added_at
        who = self.author
        if self.last_edited_at and self.last_edited_at > when:
            when = self.last_edited_at
            who = self.last_edited_by
        comments = self.comments.all()
        if len(comments) > 0:
            for c in comments:
                if c.added_at > when:
                    when = c.added_at
                    who = c.user
        return when, who