from django.core.cache import cache
from django.db.models.signals import post_delete, post_save
from django.dispatch import receiver

from .models import Material

CATEGORY_TREE_CACHE_KEY = 'material:category_tree:approved'


def invalidate_category_tree_cache():
    cache.delete(CATEGORY_TREE_CACHE_KEY)


@receiver(post_save, sender=Material)
def _on_material_saved(sender, instance, **kwargs):
    invalidate_category_tree_cache()


@receiver(post_delete, sender=Material)
def _on_material_deleted(sender, instance, **kwargs):
    invalidate_category_tree_cache()