import logging

from django.core.cache import cache
from django.conf import settings
from django.contrib.auth.models import User
from django.db import transaction

from celery.decorators import task

from questions import ANSWERS_PER_PAGE


log = logging.getLogger('k.task')


@task(rate_limit='1/s')
def update_question_votes(q):
    log.debug('Got a new QuestionVote.')
    q.sync_num_votes_past_week()
    q.save(no_update=True, force_update=True)


@task(rate_limit='15/m')
def update_question_vote_chunk(data, **kwargs):
    """Update num_votes_past_week for a number of questions."""
    log.info('Calculating past week votes for %s questions.' % len(data))

    # Import here to avoid a circle.
    from questions.models import Question

    for pk in data:
        try:
            question = Question.objects.get(pk=pk)
            question.sync_num_votes_past_week()
            question.save(no_update=True)
        except Question.DoesNotExist:
            log.debug('Missing question: %d' % pk)
    transaction.commit_unless_managed()


@task
def cache_top_contributors():
    """Compute the top contributors and store in cache."""
    log.info('Computing the top contributors.')
    sql = '''SELECT u.*, COUNT(*) AS num_solutions
             FROM auth_user AS u, questions_answer AS a,
                  questions_question AS q
             WHERE u.id = a.creator_id AND a.id = q.solution_id AND
                   a.created >= DATE_SUB(CURDATE(), INTERVAL 7 DAY)
             GROUP BY u.id
             ORDER BY num_solutions DESC
             LIMIT 10'''
    users = list(User.objects.raw(sql))
    cache.set(settings.TOP_CONTRIBUTORS_CACHE_KEY, users,
              settings.TOP_CONTRIBUTORS_CACHE_TIMEOUT)


@task(rate_limit='4/m')
def update_answer_pages(question):
    log.debug('Recalculating answer page numbers for question %s: %s' %
              (question.pk, question.title))

    i = 0
    for answer in question.answers.using('default').order_by('created').all():
        answer.page = i / ANSWERS_PER_PAGE + 1
        answer.save(no_update=True, no_notify=True)
        i += 1
