from django.db.models import Count, Q
from django.http import HttpResponse
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'])
for queue in Queue.objects.all():
    def _get_queue_length():
        return (PlaylistSong.objects
            .filter(Q(playlist=queue.playlist_id), Q(state=0) | Q(state=1))
            .count())
    queue_length_gauge.labels(name=queue).set_function(_get_queue_length)

# Export the amount of different users in the queue
queue_users_gauge = Gauge('marietje_queue_users', 'Users holding a queue at some point', ['name'])
for queue in Queue.objects.all():
    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(Q(playlist=queue.playlist_id), Q(state=0) | Q(state=1))
            .values_list('user')))
    queue_users_gauge.labels(name=queue).set_function(_get_queue_distinct_users)


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