import time
from importlib import import_module

from django.db.models.signals import post_save, post_delete
from django.conf import settings
from django.core.cache import caches
from django.dispatch import Signal
from django.contrib.contenttypes.models import ContentType

from utilities.utils import dynamic_import
from .models import Webhook


#
# Webhooks signals regiters and receivers
#

def get_or_set_webhook_cache():
    """
    Retrieve the webhook cache. If it is None set it to the current
    Webhook queryset
    """
    cache = caches['default']
    webhook_cache = cache.get('webhook_cache', None)

    if webhook_cache is None:
        webhook_cache = Webhook.objects.all()
        cache.set('webhook_cache', webhook_cache)

    return webhook_cache


def enqueue_webhooks(webhooks, model_class, data, event, signal_received_timestamp):
    """
    Serialize data and enqueue webhooks
    """
    serializer_context = {
        'request': None,
    }

    if isinstance(data, list):
        serializer_property = data[0].serializer
        serializer_cls = dynamic_import(serializer_property)
        serialized_data = serializer_cls(data, context=serializer_context, many=True)
    else:
        serializer_property = data.serializer
        serializer_cls = dynamic_import(serializer_property)
        serialized_data = serializer_cls(data, context=serializer_context)

    from django_rq import get_queue
    webhook_queue = get_queue('default')

    for webhook in webhooks:
        webhook_queue.enqueue("extras.webhooks_worker.process_webhook",
                              webhook,
                              serialized_data.data,
                              model_class,
                              event,
                              signal_received_timestamp)


def post_save_receiver(sender, instance, created, **kwargs):
    """
    Receives post_save signals from registered models. If the webhook
    backend is enabled, queue any webhooks that apply to the event.
    """
    if settings.WEBHOOK_BACKEND_ENABLED:
        signal_received_timestamp = time.time()
        webhook_cache = get_or_set_webhook_cache()
        # look for any webhooks that match this event
        updated = not created
        obj_type = ContentType.objects.get_for_model(sender)
        webhooks = [
            x
            for x in webhook_cache
            if (
                x.enabled and x.type_create == created or x.type_update == updated and
                obj_type in x.obj_type.all()
            )
        ]
        event = 'created' if created else 'updated'
        if webhooks:
            enqueue_webhooks(webhooks, sender, instance, event, signal_received_timestamp)


def post_delete_receiver(sender, instance, **kwargs):
    """
    Receives post_delete signals from registered models. If the webhook
    backend is enabled, queue any webhooks that apply to the event.
    """
    if settings.WEBHOOK_BACKEND_ENABLED:
        signal_received_timestamp = time.time()
        webhook_cache = get_or_set_webhook_cache()
        obj_type = ContentType.objects.get_for_model(sender)
        # look for any webhooks that match this event
        webhooks = [x for x in webhook_cache if x.enabled and x.type_delete and obj_type in x.obj_type.all()]
        if webhooks:
            enqueue_webhooks(webhooks, sender, instance, 'deleted', signal_received_timestamp)


def bulk_operation_receiver(sender, **kwargs):
    """
    Receives bulk_operation_signal signals from registered models. If the webhook
    backend is enabled, queue any webhooks that apply to the event.
    """
    if settings.WEBHOOK_BACKEND_ENABLED:
        signal_received_timestamp = time.time()
        event = kwargs['event']
        webhook_cache = get_or_set_webhook_cache()
        obj_type = ContentType.objects.get_for_model(sender)
        # look for any webhooks that match this event
        if event == 'created':
            webhooks = [x for x in webhook_cache if x.enabled and x.type_create and obj_type in x.obj_type.all()]
        elif event == 'updated':
            webhooks = [x for x in webhook_cache if x.enabled and x.type_update and obj_type in x.obj_type.all()]
        elif event == 'deleted':
            webhooks = [x for x in webhook_cache if x.enabled and x.type_delete and obj_type in x.obj_type.all()]
        else:
            webhooks = None

        if webhooks:
            enqueue_webhooks(webhooks, sender, list(kwargs['instances']), event, signal_received_timestamp)


# the bulk operation signal is used to overcome signals not being sent for bulk model changes
bulk_operation_signal = Signal(providing_args=["instances", "event"])
bulk_operation_signal.connect(bulk_operation_receiver)


def register_signals(senders):
    """
    Take a list of senders (Models) and register them to the post_save
    and post_delete signal receivers.
    """
    if settings.WEBHOOK_BACKEND_ENABLED:
        # only register signals if the backend is enabled
        # this reduces load by not firing signals if the
        # webhook backend feature is disabled

        for sender in senders:
            post_save.connect(post_save_receiver, sender=sender)
            post_delete.connect(post_delete_receiver, sender=sender)