@python_2_unicode_compatible
class Post(MPTTModel, NamedModel):
    uid = models.UUIDField(max_length=8, primary_key=True, default=gen_uuid, editable=False)
    content = models.TextField(blank=True, default='')
    created_by = models.ForeignKey(settings.AUTH_USER_MODEL, null=True, blank=True, on_delete=models.CASCADE, related_name='+')
    created_on = models.DateTimeField(auto_now_add=True, auto_now=False)
    modified_on = models.DateTimeField(auto_now_add=False, auto_now=True)
    parent = TreeForeignKey('self', null=True, blank=True, related_name='children', db_index=True, on_delete=models.CASCADE)
    _upvotes = models.IntegerField(blank=True, default=0)
    _downvotes = models.IntegerField(blank=True, default=0)
    wsi = models.FloatField(blank=True, default=0) # Wilson score interval
    ip_address = models.GenericIPAddressField(blank=True, null=True)
    user_agent = models.CharField(max_length=150, blank=True, null=True)

@python_2_unicode_compatible
class Thread(NamedModel):
    title = models.CharField(max_length=70, blank=False)
    slug = models.SlugField(unique=False, null=True)
    url = models.URLField(max_length=120, blank=True, default='')
    views = models.IntegerField(blank=True, default=0)
    topic = models.ForeignKey(Topic, on_delete=models.CASCADE)
    op = models.ForeignKey('Post', related_name='+', on_delete=models.CASCADE)
    locked = models.BooleanField(blank=True, default=False)

@python_2_unicode_compatible
class Topic(NamedModel):
    alphanumeric = RegexValidator(r'^[0-9a-zA-Z ]*$', 'Only alphanumeric characters are allowed.')
    title = models.CharField(max_length=20, blank=False, unique=True, validators=[alphanumeric])
    description = models.CharField(max_length=120, blank=True, default='')

    @staticmethod
    def getTopic(title):
        try:
            return Topic.objects.get(title=title)
        except ObjectDoesNotExist:
            try:
                return Topic.objects.get(title=title.replace('-', ' '))
            except ObjectDoesNotExist:
                return Topic.objects.get(title=title.replace('_', ' '))


from .models import Topic, Thread
from django.db.models import Q
def search_threads(search_term, topic_term=None):
    if topic_term:
        topic = Topic.getTopic(topic_term)
        threads_by_topic = Thread.objects.filter(topic=topic)
        threads = threads_by_topic.objects.filter(Q(title__icontains=search_term) | Q(op__content__icontains=search_term))
    else:
        threads = Thread.objects.filter(Q(title__icontains=search_term) | Q(op__content__icontains=search_term))
    return threads