# -*- coding: utf-8 -*-

from django.db.models.signals import post_save, pre_delete
from django.dispatch import receiver
from django.core.exceptions import ImproperlyConfigured

from cms.exceptions import PluginAlreadyRegistered, PluginNotRegistered
from .segment_pool import segment_pool
from ..models import SegmentBasePluginModel


@receiver(post_save)
def register_segment(sender, instance, created, **kwargs):
    '''
    Ensure that saving changes in the model results in the de-registering (if
    necessary) and registering of this segment plugin.
    '''

    if isinstance(instance, SegmentBasePluginModel):
        if not created:
            try:
                segment_pool.unregister_segment_plugin(instance)
            except (PluginAlreadyRegistered, ImproperlyConfigured):
                pass

        # Either way, we register it.
        try:
            segment_pool.register_segment_plugin(instance)
        except (PluginAlreadyRegistered, ImproperlyConfigured):
            pass


@receiver(pre_delete)
def unregister_segment(sender, instance, **kwargs):
    '''
    Listens for signals that a SegmentPlugin instance is to be deleted, and
    un-registers it from the segment_pool.
    '''

    if isinstance(instance, SegmentBasePluginModel):
        try:
            segment_pool.unregister_segment_plugin(instance)
        except (PluginNotRegistered, ImproperlyConfigured):
            pass