from django.template.loader import render_to_string
from django.db import models
from django.db.models import Count, Sum
from django.core.urlresolvers import reverse

from boards.models import Thread
from boards.models.base import Viewable


__author__ = 'neko259'


class TagManager(models.Manager):

    def get_not_empty_tags(self):
        """
        Gets tags that have non-archived threads.
        """

        tags = self.annotate(Count('threads')) \
            .filter(threads__count__gt=0).order_by('name')

        return tags


class Tag(models.Model, Viewable):
    """
    A tag is a text node assigned to the thread. The tag serves as a board
    section. There can be multiple tags for each thread
    """

    objects = TagManager()

    class Meta:
        app_label = 'boards'
        ordering = ('name',)

    name = models.CharField(max_length=100, db_index=True)
    threads = models.ManyToManyField(Thread, null=True,
                                     blank=True, related_name='tag+')

    def __unicode__(self):
        return self.name

    def is_empty(self):
        """
        Checks if the tag has some threads.
        """

        return self.get_thread_count() == 0

    def get_thread_count(self):
        return self.threads.count()

    def get_post_count(self, archived=False):
        """
        Gets posts count for the tag's threads.
        """

        posts_count = 0

        threads = self.threads.filter(archived=archived)
        if threads.exists():
            posts_count = threads.annotate(posts_count=Count('replies')) \
                .aggregate(posts_sum=Sum('posts_count'))['posts_sum']

        if not posts_count:
            posts_count = 0

        return posts_count

    def get_url(self):
        return reverse('tag', kwargs={'tag_name': self.name})

    def get_view(self, *args, **kwargs):
        return render_to_string('boards/tag.html', {
            'tag': self,
        })