import sys
import time
import logging
import traceback

try:
    import cPickle as pickle
except ImportError:
    import pickle

from django.conf import settings
from django.core.mail import mail_admins
from django.contrib.auth.models import User
from django.contrib.sites.models import Site

from lockfile import FileLock, AlreadyLocked, LockTimeout

from notification.models import NoticeQueueBatch
from notification import models as notification

# lock timeout value. how long to wait for the lock to become available.
# default behavior is to never wait for the lock to be available.
LOCK_WAIT_TIMEOUT = getattr(settings, 'NOTIFICATION_LOCK_WAIT_TIMEOUT', -1)


def send_all():
    lock = FileLock('send_notices')

    logging.debug('acquiring lock...')
    try:
        lock.acquire(LOCK_WAIT_TIMEOUT)
    except AlreadyLocked:
        logging.debug('lock already in place. quitting.')
        return
    except LockTimeout:
        logging.debug('waiting for the lock timed out. quitting.')
        return
    logging.debug('acquired.')

    batches, sent = 0, 0
    start_time = time.time()

    try:
        # nesting the try statement to be Python 2.4
        try:
            for queued_batch in NoticeQueueBatch.objects.all():
                notices = pickle.loads(
                    str(queued_batch.pickled_data).decode('base64'))
                for user, label, extra_context, on_site in notices:
                    user = User.objects.get(pk=user)
                    # FrankU: commented, because not all users get e-mailed
                    # and to supress useless logging
                    # logging.info('emitting notice to %s' % user)

                    # call this once per user to be atomic and allow for logging to
                    # accurately show how long each takes.
                    notification.send_now(
                        [user], label, extra_context, on_site)
                    sent += 1
                queued_batch.delete()
                batches += 1
        except:
            # get the exception
            exc_class, e, t = sys.exc_info()
            # email people
            current_site = Site.objects.get_current()
            subject = '[%s emit_notices] %r' % (current_site.name, e)
            message = '%s' % (
                '\n'.join(traceback.format_exception(*sys.exc_info())),)
            mail_admins(subject, message, fail_silently=True)
            # log it as critical
            logging.critical('an exception occurred: %r' % e)
    finally:
        logging.debug('releasing lock...')
        lock.release()
        logging.debug('released.')

    logging.info('')
    logging.info('%s batches, %s sent' % (batches, sent,))
    logging.info('done in %.2f seconds' % (time.time() - start_time))