from django.db.models.signals import post_save, post_delete
from django.dispatch import receiver
from django.db.models import Avg
from .models import Review

@receiver(post_save, sender=Review)
@receiver(post_delete, sender=Review)
def update_average_rating(sender, instance, **kwargs):
    """
    Update the average rating of the content object when a review is saved or deleted.
    """
    content_object = instance.content_object
    if not content_object:
        # If content object doesn't exist (orphaned review?), skip
        return

    # Check if the content object has an 'average_rating' field
    if not hasattr(content_object, 'average_rating'):
        return

    # Calculate new average
    # We query the Review model filtering by content_type and object_id
    avg_rating = Review.objects.filter(
        content_type=instance.content_type,
        object_id=instance.object_id
    ).aggregate(Avg('rating'))['rating__avg']

    # Update field
    content_object.average_rating = avg_rating or 0  # Default to 0 if no reviews
    content_object.save(update_fields=['average_rating'])