wordpress-event-bridge-for-activitypub/docs/README.md

Developer documentation

Overview

The entry point of the plugin is the initialization of the singleton class \Event_Bridge_For_ActivityPub\Setup in the main plugin file event-bridge-for-activitypub.php. The constructor of that class calls its setup_hooks() function. This function provides hooks that initialize all parts of the Event Bridge For ActivityPub whenever needed.

File structure

Note that almost all files and folder within the activitypub folders are structured the same way as in the WordPress ActivityPub plugin.

Event Plugin Integrations

This plugin supports multiple event plugins, even at the same time. To add a new one you first need to add some basic information about your event plugin. Just create a new file in ./includes/integrations/my-event-plugin.php. Implement at least all abstract functions of the Event_Plugin_Integration class.

Basic Event Plugin Integration

  namespace Event_Bridge_For_ActivityPub\Integrations;

  // Exit if accessed directly.
  defined( 'ABSPATH' ) || exit; // @codeCoverageIgnore

  /**
   * Integration information for My Event Plugin
   *
   * This class defines necessary meta information is for the integration of My Event Plugin with the ActivityPub plugin.
   */
  final class My_Event_Plugin extends Event_Plugin_Integration {

Registering an Event Plugin Integration

Then you need to tell the Event Bridge for ActivityPub about that class by adding it to the EVENT_PLUGIN_INTEGRATIONS constant in the includes/setup.php file:

	private const EVENT_PLUGIN_INTEGRATIONS = array(
		...
		\Event_Bridge_For_ActivityPub\Integrations\My_Event_Plugin::class,
	);

Additional Feature: Event Sources

Not all Event Plugin Integrations support the event-sources feature. To add support for it an integration must implement the Feature_Event_Sources interface.

namespace Event_Bridge_For_ActivityPub\Integrations;

// Exit if accessed directly.
defined( 'ABSPATH' ) || exit; // @codeCoverageIgnore

  /**
   * Integration information for My Event Plugin.
   *
   * This class defines necessary meta information is for the integration of My Event Plugin with the ActivityPub plugin.
   * This integration supports the Event Sources Feature.
   */
final class GatherPress extends Event_Plugin_Integration implements Feature_Event_Sources {

Transformer

Transformers are the classes that convert an WordPress post type (e.g. one used for events) to ActivityStreams. The Event Bridge for ActivityPub then takes care of applying the transformer, so you can jump right into implementing it.

Event Sources Feature – Transmogrifier

The event sources feature allows to aggregate events from external ActivityPub actors. As the initialization of the Event-Sources feature is quite complex all of that initialization is done in the init function of the file includes/class-event-sources.php which is called by the \Event_Bridge_For_ActivityPub\Setup class (includes/class-setup.php).

In this plugin we call a Transmogrifier the opposite of a Transformer. It takes care of converting an ActivityPub (Event) object in ActivityStreams to the WordPress representation of an event plugin. The transmogrifier classes are only used when the Event Sources feature is activated. The Event Bridge For ActivityPub can register transformers for multiple event plugins at the same time, however only one transmogrifier, that is one target even plugin can be used as a target for incoming external ActivityPub Event objects.