import logging
from datetime import timedelta
from celery import task
from django.db.models import Q, F
from django.db import transaction
from django.conf import settings
from django.utils import timezone
from django.template.loader import get_template
from django.core.mail import send_mass_mail
from constance import config as site_config
import django_lcore

from ccvpn.common import parse_integer_list
from lambdainst.models import User, VPNUser

ROOT_URL = settings.ROOT_URL
SITE_NAME = settings.TICKETS_SITE_NAME

logger = logging.getLogger(__name__)


@task(autoretry_for=(Exception,), default_retry_delay=60*60)
def push_all_users():
    for u in User.objects.all():
        # skip 'empty' accounts
        if u.vpnuser.expiration is None:
            continue

        logger.debug("pushing user %r", u)

        django_lcore.sync_user(u.vpnuser, fail_silently=False)


@task(autoretry_for=(Exception,), max_retries=10, retry_backoff=True)
def push_user(user_id):
    user = User.objects.get(id=user_id)
    logger.debug("pushing user %r", user)
    django_lcore.sync_user(user.vpnuser, fail_silently=False)


@task
def notify_account_expiration():
    """ Notify users near the end of their subscription """
    from_email = settings.DEFAULT_FROM_EMAIL

    for v in parse_integer_list(site_config.NOTIFY_DAYS_BEFORE):
        emails = []
        users = list(get_next_expirations(v))
        logging.info("sending -%d day notification to %d users", v, len(users))

        with transaction.atomic():
            for u in users:
                # Ignore users with active subscriptions
                # They will get notified only if it gets cancelled (payments
                # processors will cancel after a few failed payments)
                if u.get_subscription():
                    continue

                ctx = dict(site_name=SITE_NAME, user=u.user,
                            exp=u.expiration, url=ROOT_URL)
                text = get_template('lambdainst/mail_expire_soon.txt').render(ctx)
                emails.append(("CCrypto VPN Expiration", text, from_email, [u.user.email]))
                logging.debug("sending -%d days notify to %s" % (v, u.user.email))

                u.last_expiry_notice = timezone.now()
                u.save()

            send_mass_mail(emails)


def get_next_expirations(days=3):
    """ Gets users whose subscription will expire in some days """

    limit_date = timezone.now() + timedelta(days=days)

    users = VPNUser.objects.exclude(user__email__exact='')

    users = users.filter(expiration__gt=timezone.now())  # Not expired
    users = users.filter(expiration__lt=limit_date)  # Expire in a few days

    # Make sure we dont send the notice twice
    users = users.filter(Q(last_expiry_notice__isnull=True)
                         | Q(expiration__gt=F('last_expiry_notice')
                             + timedelta(days=days)))
    return users