from django.contrib.auth import get_user_model
from django.contrib.contenttypes.models import ContentType
from django.db.models.signals import post_delete, post_save, pre_delete
from django.dispatch import receiver
from schedule.models import Calendar, Event

from .realtime import get_calendar_recipient_ids, send_calendar_update


def _relation_user_id(instance) -> int | None:
    User = get_user_model()
    user_content_type = ContentType.objects.get_for_model(User)
    if instance.content_type_id != user_content_type.id:
        return None
    return instance.object_id


@receiver(post_save, sender="schedule.Event")
def broadcast_event_saved(sender, instance, created, **kwargs):
    calendar = instance.calendar
    send_calendar_update(
        action="created" if created else "updated",
        entity="event",
        calendar_id=calendar.id,
        event_id=instance.id,
        changed_fields=getattr(instance, "_changed_fields", []),
        recipient_ids=get_calendar_recipient_ids(calendar, event=instance),
        extra={
            "start": instance.start.isoformat() if instance.start else None,
            "end": instance.end.isoformat() if instance.end else None,
            "is_recurring": bool(instance.rule_id),
        },
    )


@receiver(pre_delete, sender="schedule.Event")
def broadcast_event_deleted(sender, instance, **kwargs):
    send_calendar_update(
        action="deleted",
        entity="event",
        calendar_id=instance.calendar_id,
        event_id=instance.id,
        recipient_ids=get_calendar_recipient_ids(instance.calendar, event=instance),
        extra={
            "start": instance.start.isoformat() if instance.start else None,
            "end": instance.end.isoformat() if instance.end else None,
            "is_recurring": bool(instance.rule_id),
        },
    )


@receiver(post_save, sender="schedule.Calendar")
def broadcast_calendar_saved(sender, instance, created, **kwargs):
    recipients = get_calendar_recipient_ids(instance)
    if not recipients:
        return
    send_calendar_update(
        action="created" if created else "updated",
        entity="calendar",
        calendar_id=instance.id,
        recipient_ids=recipients,
    )


@receiver(pre_delete, sender="schedule.Calendar")
def broadcast_calendar_deleted(sender, instance, **kwargs):
    send_calendar_update(
        action="deleted",
        entity="calendar",
        calendar_id=instance.id,
        recipient_ids=get_calendar_recipient_ids(instance),
    )


@receiver(post_save, sender="schedule.CalendarRelation")
def broadcast_calendar_relation_saved(sender, instance, **kwargs):
    recipients = get_calendar_recipient_ids(instance.calendar)
    relation_user_id = _relation_user_id(instance)
    if relation_user_id:
        recipients.add(relation_user_id)
    send_calendar_update(
        action="membership_changed",
        entity="calendar",
        calendar_id=instance.calendar_id,
        recipient_ids=recipients,
    )


@receiver(post_delete, sender="schedule.CalendarRelation")
def broadcast_calendar_relation_deleted(sender, instance, **kwargs):
    calendar = Calendar.objects.filter(pk=instance.calendar_id).first()
    recipients = get_calendar_recipient_ids(calendar)
    relation_user_id = _relation_user_id(instance)
    if relation_user_id:
        recipients.add(relation_user_id)
    send_calendar_update(
        action="membership_changed",
        entity="calendar",
        calendar_id=instance.calendar_id,
        recipient_ids=recipients,
    )


@receiver([post_save, post_delete], sender="schedule.EventRelation")
def broadcast_event_relation_changed(sender, instance, **kwargs):
    event = (
        Event.objects.select_related("calendar").filter(pk=instance.event_id).first()
    )
    if event is None:
        return
    recipients = get_calendar_recipient_ids(event.calendar, event=event)
    relation_user_id = _relation_user_id(instance)
    if relation_user_id:
        recipients.add(relation_user_id)
    send_calendar_update(
        action="membership_changed",
        entity="event",
        calendar_id=event.calendar_id,
        event_id=event.id,
        recipient_ids=recipients,
    )