from django.http import HttpResponse
from django.db.utils import OperationalError

from prometheus_client import generate_latest, Gauge

from queues.models import Queue, PlaylistSong

# Export queue length
queue_length_gauge = Gauge('marietje_queue_length', 'Marietje queue length', ['name'])
# Export the queue duration
queue_duration_gauge = Gauge('marietje_queue_duration', 'Marietje queue duration in seconds', ['name'])
# Export the amount of different users in the queue
queue_users_gauge = Gauge('marietje_queue_users', 'Users holding a queue at some point', ['name'])

try:
    for queue in Queue.objects.all():
        def _get_queue_length():
            return PlaylistSong.objects.filter(playlist=queue.playlist_id, state=0).count()

        def _get_queue_duration():
            playlist_songs = (PlaylistSong.objects.filter(playlist=queue.playlist_id, state=0)
                              .select_related('song')
                              .all())
            return sum(ps.song.duration for ps in playlist_songs)

        def _get_queue_distinct_users():
            # Ideally, we would use .distinct() here, but it is not supported on
            # sqlite3. This makes testing a bit tedious. Also, it does not give me
            # that much of confidence that it would also work on mysql.
            # Furtermore, we do not expect the queue to be very long at any moment.
            return len(set(PlaylistSong.objects.filter(playlist=queue.playlist_id, state=0)
                           .values_list('user')))

        queue_length_gauge.labels(name=queue).set_function(_get_queue_length)
        queue_duration_gauge.labels(name=queue).set_function(_get_queue_duration)
        queue_users_gauge.labels(name=queue).set_function(_get_queue_distinct_users)

except OperationalError:
    pass


def metrics(request):
    return HttpResponse(generate_latest(), content_type="text/plain")