Calendar events and iCal feeds

aleksis/core/mixins.py

@@ -22,6 +22,7 @@ from django.views.generic import CreateView, UpdateView
 from django.views.generic.edit import DeleteView, ModelFormMixin
 
 import reversion
+from django_ical.feedgenerator import ITEM_EVENT_FIELD_MAP, ICal20Feed
 from dynamic_preferences.settings import preferences_settings
 from dynamic_preferences.types import FilePreference
 from guardian.admin import GuardedModelAdmin
@@ -575,3 +576,74 @@ class RegistryObject:
     @classmethod
     def get_object_by_name(cls, name):
         cls.registered_objects_dict.get(name)
+
+
+class CalendarEventMixin(RegistryObject):
+    name: str = ""  # The source name
+    verbose_name: str = ""  # The shown name of the feed
+    link: str = ""
+    description: str = ""
+
+    @classmethod
+    def get_verbose_name(cls):
+        return cls.verbose_name
+
+    @classmethod
+    def get_link(cls):
+        return cls.link
+
+    @classmethod
+    def get_description(cls):
+        return cls.description
+
+    @classmethod
+    def get_language(cls):
+        return "en"  # FIXME
+
+    @classmethod
+    def create_event(cls, reference_object, feed: ICal20Feed):
+        values = {}
+        for field in cls.get_event_field_names():
+            field_value = cls.get_event_field_value(reference_object, field)
+            if field_value is not None:
+                values[field] = field_value
+        feed.add_item(**values)
+        return values
+
+    @classmethod
+    def start_feed(cls):
+        feed = ICal20Feed(
+            title=cls.get_verbose_name(),
+            link=cls.get_link(),
+            description=cls.get_description(),
+            language=cls.get_language(),
+        )
+        return feed
+
+    @classmethod
+    def get_objects(cls):
+        raise NotImplementendError
+
+    @classmethod
+    def create_feed(cls):
+        feed = cls.start_feed()
+
+        for reference_object in cls.get_objects():
+            cls.create_event(reference_object, feed)
+
+        return feed
+
+    @classmethod
+    def get_event_field_names(cls):
+        return [field_map[0] for field_map in ITEM_EVENT_FIELD_MAP]
+
+    @classmethod
+    def get_event_field_value(cls, reference_object, field_name):
+        method_name = f"value_{field_name}"
+        if hasattr(cls, method_name) and callable(getattr(cls, method_name)):
+            return getattr(cls, method_name)(reference_object)
+        return None
+
+    @classmethod
+    def value_link(cls, reference_object):
+        return ""