Merge pull request #194 from pinry/feature/plugin-system

Feature: Add naive plugin support for pinry

docs/src/plugin-system.md

@@ -0,0 +1,20 @@
+# New plugin system for Pinry
+
+New plugin system is under development.
+
+Now you could access it via project example plugin file `pinry_plugins/batteries/plugin_example.py`.
+
+You could create a simple plugin which has a class which owns methods named:
+
++ process_image_pre_creation
++ process_thumbnail_pre_creation
+ 
+And, add the plugin class to local_settings.py as:
+
+```
+ENABLED_PLUGINS = [
+    'pinry_plugins.batteries.plugin_example.Plugin',
+]
+```
+
+Now the plugin will work like a charm!

mkdocs.yml

@@ -19,6 +19,7 @@ nav:
   - Theories: 'theories.md'
   - Install with Docker: 'install-with-docker.md'
   - Development: 'development.md'
+  - PluginSystem: 'plugin-system.md'
   - Docs: 'docs.md'
   - Passwords: 'passwords.md'
   - Assets: 'assets.md'

pinry/settings/base.py

@@ -21,6 +21,7 @@ INSTALLED_APPS = [
     'django_images',
     'core',
     'users',
+    'pinry_plugins.apps.PinryPluginsConfig',
 ]
 
 ROOT_URLCONF = 'pinry.urls'

pinry/settings/local_settings.example.py

@@ -42,3 +42,7 @@ IMAGE_SIZES = {
 
 # Whether people can view pins without login
 PUBLIC = True
+
+ENABLED_PLUGINS = [
+    'pinry_plugins.batteries.plugin_example.Plugin',
+]

pinry_plugins/apps.py

@@ -0,0 +1,9 @@
+from django.apps import AppConfig
+
+
+class PinryPluginsConfig(AppConfig):
+    name = 'pinry_plugins'
+
+    def ready(self):
+        from pinry_plugins import builder   # noqa
+        builder.init()

pinry_plugins/batteries/plugin_example.py

@@ -0,0 +1,10 @@
+from core.models import Image
+from django_images.models import Thumbnail
+
+
+class Plugin:
+    def process_image_pre_creation(self, django_settings, image_instance: Image):
+        pass
+
+    def process_thumbnail_pre_creation(self, django_settings, thumbnail_instance: Thumbnail):
+        pass

pinry_plugins/builder/__init__.py

@@ -0,0 +1,5 @@
+from . import _loader
+
+
+def init():
+    _loader.init()

pinry_plugins/builder/_loader.py

@@ -0,0 +1,63 @@
+import logging
+
+from django.dispatch import receiver
+from django.utils.module_loading import import_string
+from django.conf import settings
+from django.db import models
+
+from core.models import Image
+from django_images.models import Thumbnail
+
+_plugins = getattr(settings, "ENABLED_PLUGINS", [])
+_plugin_instances = []
+
+
+def _load_plugins():
+    for plugin_path in _plugins:
+        plugin_cls = import_string(plugin_path)
+        _plugin_instances.append(plugin_cls())
+
+
+@receiver(models.signals.pre_save, sender=Image)
+def process_image_pre_creation(sender, instance: Image, **kwargs):
+    # FIXME(winkidney): May have issue on determining if it
+    #  is created or not
+    if instance.pk is not None:
+        return
+    for plugin in _plugin_instances:
+        process_fn = getattr(plugin, "process_image_pre_creation")
+        try:
+            process_fn(
+                django_settings=settings,
+                image_instance=instance,
+            )
+        except Exception:
+            logging.exception(
+                "Error occurs while trying to access plugin's pin_pre_save "
+                "for plugin %s" % plugin
+            )
+
+
+@receiver(models.signals.pre_save, sender=Thumbnail)
+def process_thumbnail_pre_creation(sender, instance: Thumbnail, **kwargs):
+    # FIXME(winkidney): May have issue on determining if it
+    #  is created or not
+    if instance.pk is not None:
+        return
+
+    for plugin in _plugin_instances:
+        process_fn = getattr(plugin, "process_thumbnail_pre_creation")
+        try:
+            process_fn(
+                django_settings=settings,
+                thumbnail_instance=instance,
+            )
+        except Exception:
+            logging.exception(
+                "Error occurs while trying to access plugin's process_thumbnail_pre_creation "
+                "for plugin %s" % plugin
+            )
+
+
+def init():
+    _load_plugins()