"""Reacts to an admin editing a PlaceSettings row (grid size, end time) by:

1. Rebuilding that event's Redis canvas from history at the (possibly new)
   dimensions - a resize invalidates the old Redis bytes (wrong length,
   wrong meaning), so this keeps Redis self-healing instead of relying on
   the admin remembering to click "Resync canvas from DB" after every
   resize.
2. Pushing the new settings to that event's already-connected clients. Unlike
   the clock app, place has no periodic heartbeat broadcast to piggyback
   this onto, so it's broadcast explicitly here instead.
3. Queueing the wipe for the end time, if any (see tasks.py).
"""

from asgiref.sync import async_to_sync
from channels.layers import get_channel_layer
from django.db.models.signals import post_save
from django.dispatch import receiver

from .broadcast import place_group
from .canvas import rebuild_canvas_from_history
from .models import PlaceSettings
from .tasks import schedule_wipe
from .wire import to_epoch_ms


@receiver(post_save, sender=PlaceSettings)
def on_settings_saved(sender, instance, **kwargs):
    rebuild_canvas_from_history(instance.event, instance.width, instance.height)
    schedule_wipe(instance)

    channel_layer = get_channel_layer()
    if channel_layer is None:
        return
    async_to_sync(channel_layer.group_send)(
        place_group(instance.event.path),
        {
            "type": "settings_changed",
            "width": instance.width,
            "height": instance.height,
            "ends_at": (
                None
                if instance.placement_ends_at is None
                else to_epoch_ms(instance.placement_ends_at)
            ),
        },
    )