from django.core.management.base import BaseCommand
from django.db import transaction
from django.db.models import Exists, OuterRef
from django.utils.translation import gettext_lazy as _

from apps.chat.models import RoomMessage
from apps.course.models import Course


class Command(BaseCommand):
    help = _('Ensure every course has a group chat room')

    def add_arguments(self, parser):
        parser.add_argument(
            '--dry-run',
            action='store_true',
            dest='dry_run',
            help=_('Show courses missing group rooms without creating them'),
        )

    def handle(self, *args, **options):
        dry_run = options['dry_run']

        group_room_exists = RoomMessage.objects.filter(
            course=OuterRef('pk'),
            room_type=RoomMessage.RoomTypeChoices.GROUP,
        )

        courses_without_group_room = Course.objects.prefetch_related('professors').annotate(
            has_group_room=Exists(group_room_exists)
        ).filter(
            has_group_room=False
        )

        missing_count = courses_without_group_room.count()

        if missing_count == 0:
            self.stdout.write(self.style.SUCCESS(_('All courses already have a group room.')))
            return

        self.stdout.write(self.style.WARNING(_(f'Found {missing_count} course(s) without a group room.')))

        for course in courses_without_group_room:
            self.stdout.write(f'- Course #{course.id}: {course.title}')

        if dry_run:
            self.stdout.write(self.style.WARNING(_('Dry run completed. No rooms were created.')))
            return

        created_count = 0
        with transaction.atomic():
            for course in courses_without_group_room:
                RoomMessage.objects.create(
                    name=f"{course.title} - Group",
                    description=f"Group chat for course: {course.title}",
                    initiator=course.professors.first(),
                    course=course,
                    room_type=RoomMessage.RoomTypeChoices.GROUP,
                    is_locked=course.is_group_chat_locked,
                )
                created_count += 1

        self.stdout.write(self.style.SUCCESS(_(f'Created {created_count} missing group room(s).')))