Added subscription and observers module.

.gitignore

@@ -1 +1,7 @@
 .idea/
+
+*.sqlite3
+*.pyc
+__pycache__/
+
+*.egg-info/

MANIFEST.in

@@ -0,0 +1,4 @@
+include *.py
+include *.txt
+recursive-include django_model_subscription *.py
+recursive-include model_subscription *.py

demo/admin.py

@@ -0,0 +1,3 @@
+from django.contrib import admin
+
+# Register your models here.

demo/apps.py

@@ -0,0 +1,8 @@
+from django.apps import AppConfig
+
+
+class DemoConfig(AppConfig):
+    name = 'demo'
+
+    def ready(self):
+        from demo import subscription

demo/migrations/0001_initial.py

@@ -0,0 +1,26 @@
+# Generated by Django 2.2.6 on 2019-10-20 16:27
+
+from django.db import migrations, models
+import model_subscription.mixin
+
+
+class Migration(migrations.Migration):
+
+    initial = True
+
+    dependencies = [
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='TestModel',
+            fields=[
+                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('name', models.CharField(max_length=20)),
+            ],
+            options={
+                'abstract': False,
+            },
+            bases=(model_subscription.mixin.SubscriptionModelMixin, models.Model),
+        ),
+    ]

demo/models.py

@@ -0,0 +1,8 @@
+from django.db import models
+
+# Create your models here.
+from model_subscription.models import SubscriptionModel
+
+
+class TestModel(SubscriptionModel):
+    name = models.CharField(max_length=20)

demo/subscription.py

@@ -0,0 +1,16 @@
+from demo.models import TestModel
+from model_subscription.constants import OperationType
+from model_subscription.decorators import subscribe, create_subscription, unsubscribe_create
+
+
+@subscribe(OperationType.CREATE, TestModel)
+def handle_create_1(instance):
+    print('1. Created {}'.format(instance.name))
+
+
+@create_subscription(TestModel)
+def handle_create_2(instance):
+    print('2. Created {}'.format(instance.name))
+
+
+unsubscribe_create(TestModel, handle_create_2)

demo/tests.py

@@ -0,0 +1,18 @@
+from django.test import TestCase
+
+# Create your tests here.
+import os
+
+import django
+from django.conf import settings
+
+# Create your tests here.
+
+if __name__ == '__main__':
+    os.environ['DJANGO_SETTINGS_MODULE'] = 'django_model_subscription.settings'
+    django.setup()
+
+    from demo.models import TestModel
+
+
+    t = TestModel.objects.create(name='test')

django_model_subcription/settings.py → django_model_subscription/settings.py

@@ -1,5 +1,5 @@
 """
-Django settings for django_model_subcription project.
+Django settings for django_model_subscription project.
 
 Generated by 'django-admin startproject' using Django 2.0.2.
 
@@ -37,6 +37,8 @@
     'django.contrib.sessions',
     'django.contrib.messages',
     'django.contrib.staticfiles',
+    'model_subscription',
+    'demo',
 ]
 
 MIDDLEWARE = [
@@ -49,7 +51,7 @@
     'django.middleware.clickjacking.XFrameOptionsMiddleware',
 ]
 
-ROOT_URLCONF = 'django_model_subcription.urls'
+ROOT_URLCONF = 'django_model_subscription.urls'
 
 TEMPLATES = [
     {
@@ -67,7 +69,9 @@
     },
 ]
 
-WSGI_APPLICATION = 'django_model_subcription.wsgi.application'
+WSGI_APPLICATION = 'django_model_subscription.wsgi.application'
+
+SUBSCRIPTION_MODULE = 'subscription'
 
 
 # Database

django_model_subcription/urls.py → django_model_subscription/urls.py

@@ -1,4 +1,4 @@
-"""django_model_subcription URL Configuration
+"""django_model_subscription URL Configuration
 
 The `urlpatterns` list routes URLs to views. For more information please see:
     https://docs.djangoproject.com/en/2.0/topics/http/urls/

django_model_subcription/wsgi.py → django_model_subscription/wsgi.py

@@ -1,5 +1,5 @@
 """
-WSGI config for django_model_subcription project.
+WSGI config for django_model_subscription project.
 
 It exposes the WSGI callable as a module-level variable named ``application``.
 
@@ -11,6 +11,6 @@
 
 from django.core.wsgi import get_wsgi_application
 
-os.environ.setdefault("DJANGO_SETTINGS_MODULE", "django_model_subcription.settings")
+os.environ.setdefault("DJANGO_SETTINGS_MODULE", "django_model_subscription.settings")
 
 application = get_wsgi_application()

manage.py

@@ -3,7 +3,7 @@
 import sys
 
 if __name__ == "__main__":
-    os.environ.setdefault("DJANGO_SETTINGS_MODULE", "django_model_subcription.settings")
+    os.environ.setdefault("DJANGO_SETTINGS_MODULE", "django_model_subscription.settings")
     try:
         from django.core.management import execute_from_command_line
     except ImportError as exc:

model_subscription/__init__.py

@@ -0,0 +1,3 @@
+VERSION = (0, 0, 1)
+
+__version__ = '.'.join(map(str, VERSION))

model_subscription/constants.py

@@ -0,0 +1,7 @@
+from enum import Enum
+
+
+class OperationType(str, Enum):
+    CREATE = 'create'
+    UPDATE = 'update'
+    DELETE = 'delete'

model_subscription/decorators.py

@@ -0,0 +1,69 @@
+from functools import partial
+from typing import Callable, Optional
+
+from django.db import models
+
+from model_subscription.constants import OperationType
+from model_subscription.mixin import SubscriptionModelMixin
+
+"""
+@subscribe(OperationType.CREATE, TestModel)
+def my_custom_receiver(instance)
+    pass
+
+@subscribe(OperationType.UPDATE, TestModel)
+def my_custom_receiver(instance, updated_data)
+    pass
+
+@subscribe(OperationType.DELETE, TestModel)
+def my_custom_receiver(instance)
+    pass 
+"""
+
+"""
+@create_subscription(TestModel)
+def my_custom_receiver(instance)
+    pass
+
+
+@update_subscription(TestModel)
+def my_custom_receiver(instance, updated_data)
+    pass
+
+
+@delete_subscription(TestModel)
+def my_custom_receiver(test_instance)
+    pass
+
+"""
+
+
+def subscribe(operation, model):
+    # type: ((SubscriptionModelMixin, models.Model), OperationType) -> Callable
+    def _decorator(func):
+        model._subscription.attach(operation, func)
+        return func
+    return _decorator
+
+
+create_subscription = partial(subscribe, OperationType.CREATE)
+update_subscription = partial(subscribe, OperationType.UPDATE)
+delete_subscription = partial(subscribe, OperationType.DELETE)
+
+
+def unsubscribe(operation, model, func=None):
+    # type: ((SubscriptionModelMixin, models.Model), OperationType, Optional[Callable]) -> Callable
+
+    if func is not None:
+        model._subscription.detach(operation, func)
+        return func
+
+    def _decorator(inner):
+        model._subscription.detach(operation, inner)
+        return inner
+    return _decorator
+
+
+unsubscribe_create = partial(unsubscribe, OperationType.CREATE)
+unsubscribe_update = partial(unsubscribe, OperationType.UPDATE)
+unsubscribe_delete = partial(unsubscribe, OperationType.DELETE)

model_subscription/mixin.py

@@ -0,0 +1,42 @@
+from django.db.models.base import ModelBase
+from django.utils import six
+from django_lifecycle import LifecycleModelMixin, hook
+
+from model_subscription.constants import OperationType
+from model_subscription.subscriber import ModelSubscription
+
+
+class SubscriptionMeta(ModelBase):
+    """
+    The Singleton class can be implemented in different ways in Python. Some
+    possible methods include: base class, decorator, metaclass. We will use the
+    metaclass because it is best suited for this purpose.
+    """
+
+    def __new__(cls, name, bases, attrs):
+        for base in bases:
+            if hasattr(bases, '_subscription'):
+                del base['_subscription']
+        _subscription = ModelSubscription()
+        attrs['_subscription'] = _subscription
+        return super(SubscriptionMeta, cls).__new__(cls, name, bases, attrs)
+
+
+@six.add_metaclass(SubscriptionMeta)
+class SubscriptionModelMixin(LifecycleModelMixin):
+    def __init__(self, *args, **kwargs):
+        self._subscription.subscription_model = self
+        self._subscription.auto_discover()
+        super(SubscriptionModelMixin, self).__init__(*args, **kwargs)
+
+    @hook('after_create')
+    def notify_create(self):
+        self._subscription.notify(OperationType.CREATE)
+
+    @hook('after_update')
+    def notify_update(self):
+        self._subscription.notify(OperationType.UPDATE)
+
+    @hook('after_delete')
+    def notify_delete(self):
+        self._subscription.notify(OperationType.DELETE)

model_subscription/models.py

@@ -1,3 +1,8 @@
 from django.db import models
 
-# Create your models here.
+from model_subscription.mixin import SubscriptionModelMixin
+
+
+class SubscriptionModel(SubscriptionModelMixin, models.Model):
+    class Meta:
+        abstract = True

model_subscription/observers.py

@@ -0,0 +1,78 @@
+from abc import ABC, abstractmethod
+from typing import Callable, Any, List, Tuple, Union
+
+from django.db import models
+
+from model_subscription.constants import OperationType
+
+
+class Observer(ABC):
+    """
+    The Observer interface declares the update method.
+    """
+
+    def __init__(self):
+        self._receivers = []  # type: List[Tuple[int, Callable[[models.Model, dict], Any]]]
+
+    @property
+    @abstractmethod
+    def action(self):
+        pass
+
+    @abstractmethod
+    def handle(self, instance, changed_data):
+        # type: (models.Model, dict) -> None
+        """
+        Receive update from subject.
+        """
+        pass
+
+    @property
+    def receivers(self):
+        return self._receivers
+
+    @receivers.setter
+    def receivers(self, other):
+        # type: (Union[Callable, list]) -> None
+        if isinstance(other, list):
+            for receiver in other:
+                if id(receiver) not in [x[0] for x in self._receivers]:
+                    self._receivers.append((id(receiver), receiver))
+        else:
+            if id(other) not in [x[0] for x in self._receivers]:
+                self._receivers.append((id(other), other))
+
+    @receivers.deleter
+    def receivers(self):
+        self._receivers = []
+
+"""
+Concrete Observers react to the operations issued by the Model they have been attached to.
+"""
+
+
+class CreateObserver(Observer):
+    action = OperationType.CREATE
+
+    def handle(self, instance, changed_data):
+        # type: (models.Model, dict) -> None
+        for _, receiver in self.receivers:
+            receiver(instance)
+
+
+class UpdateObserver(Observer):
+    action = OperationType.UPDATE
+
+    def handle(self, instance, changed_data):
+        # type: (models.Model, dict) -> None
+        for _, receiver in self.receivers:
+            receiver(instance, changed_data)
+
+
+class DeleteObserver(Observer):
+    action = OperationType.DELETE
+
+    def handle(self, instance, changed_data):
+        # type: (models.Model, dict) -> None
+        for _, receiver in self.receivers:
+            receiver(instance)