Register custom ActivityPub transformer for the GatherPress Event post-type

includes/core/classes/activitypub/class-event-transformer.php

@@ -0,0 +1,235 @@
+<?php
+/**
+ * Manages transformation of the GatherPress object to ActivityPub.
+ *
+ * This class is responsible defining getter functions for all common event
+ * properties of an extended ActivityPub event object and governing the
+ * transformation process.
+ *
+ * @package GatherPress\Core\Activitypub
+ * @since 1.0.0
+ */
+
+namespace GatherPress\Core\ActivityPub;
+
+use function Activitypub\get_rest_url_by_path;
+
+/**
+ * Class Event_Transformer.
+ *
+ * Extending the common Post Transformer.
+ *
+ * @since 1.0.0
+ */
+class Event_Transformer extends \Activitypub\Transformer\Post {
+	/**
+	 * The current GatherPress Event object.
+	 *
+	 * @var Event
+	 */
+	protected $gp_event;
+
+	/**
+	 * Get transformer name.
+	 *
+	 * Retrieve the transformers name.
+	 *
+	 * @since 1.0.0
+	 * @access public
+	 * @return string Widget name.
+	 */
+	public function get_transformer_name() {
+		return 'gatherpress/gp-event';
+	}
+
+	/**
+	 * Get transformer title.
+	 *
+	 * Retrieve the transformers label.
+	 *
+	 * @since 1.0.0
+	 * @access public
+	 * @return string Widget title.
+	 */
+	public function get_transformer_label() {
+		return 'GatherPress Event';
+	}
+
+	/**
+	 * Get supported post types.
+	 *
+	 * Retrieve the list of supported WordPress post types this transformer widget can handle.
+	 *
+	 * @since 1.0.0
+	 * @access public
+	 * @return array Widget categories.
+	 */
+	public static function get_supported_post_types() {
+		return array( \GatherPress\Core\Event::POST_TYPE );
+	}
+
+	/**
+	 * Returns the ActivityStreams 2.0 Object-Type for an Event.
+	 *
+	 * @see https://www.w3.org/TR/activitystreams-vocabulary/#dfn-event
+	 * @since 1.0.0
+	 * @return string The Event Object-Type.
+	 */
+	protected function get_type() {
+		return 'Event';
+	}
+
+	/**
+	 * Get the event location.
+	 *
+	 * @return array The Place.
+	 */
+	public function get_location() {
+        $venue  = $this->gp_event->get_venue_information();
+		$address = $venue['full_address'];
+		$place   = new \Activitypub\Activity\Extended_Object\Place();
+		$place->set_type( 'Place' );
+		$place->set_name( $address );
+		$place->set_address( $address );
+		return $place;
+	}
+
+	/**
+	 * Get the end time from the event object.
+	 */
+	protected function get_end_time() {
+		return $this->gp_event->get_datetime_end( 'Y-m-d\TH:i:s\Z' );
+	}
+
+	/**
+	 * Get the end time from the event object.
+	 */
+	protected function get_start_time() {
+		return $this->gp_event->get_datetime_start( 'Y-m-d\TH:i:s\Z' );
+	}
+
+	/**
+	 * Get the event link from the events metadata.
+	 */
+	private function get_event_link() {
+		$event_link = get_post_meta( $this->wp_object->ID, 'event-link', true );
+		if ( $event_link ) {
+			return array(
+				'type'      => 'Link',
+				'name'      => 'Website',
+				'href'      => \esc_url( $event_link ),
+				'mediaType' => 'text/html',
+			);
+		}
+	}
+
+	/**
+	 * Overrides/extends the get_attachments function to also add the event Link.
+	 */
+	protected function get_attachment() {
+		$attachments = parent::get_attachment();
+		if ( count( $attachments ) ) {
+			$attachments[0]['name'] = 'Banner';
+			$attachments[0]['type'] = 'Document';
+		}
+		$event_link = $this->get_event_link();
+		if ( $event_link ) {
+			$attachments[] = $this->get_event_link();
+		}
+		return $attachments;
+	}
+
+	/**
+	 * TODO:
+	 *
+	 * @return string $category
+	 */
+	protected function get_category() {
+		return 'MEETING';
+	}
+
+	/**
+	 * Create a custom summary.
+	 *
+	 * It contains also the most important meta-information. The summary is often used when the
+	 * ActivityPub object type 'Event' is not supported, e.g. in Mastodon.
+	 *
+	 * @return string $summary The custom event summary.
+	 */
+	public function get_summary() {
+		if ( $this->wp_object->excerpt ) {
+			$excerpt = $this->wp_object->post_excerpt;
+		} elseif ( get_post_meta( $this->wp_object->ID, 'event-summary', true ) ) {
+			$excerpt = get_post_meta( $this->wp_object->ID, 'event-summary', true );
+		} else {
+			$excerpt = $this->get_content();
+		}
+
+		$address           = get_post_meta( $this->wp_object->ID, 'event-location', true );
+		$start_time        = get_post_meta( $this->wp_object->ID, 'event-start-date', true );
+		$datetime_format   = get_option( 'date_format' ) . ' ' . get_option( 'time_format' );
+		$start_time_string = wp_date( $datetime_format, $start_time );
+		$summary           = "📍 {$address}\n📅 {$start_time_string}\n\n{$excerpt}";
+		return $summary;
+	}
+
+	public function get_to() {
+		$path = sprintf( 'users/%d/followers', intval( $this->wp_object->post_author ) );
+
+		return array(
+				'https://www.w3.org/ns/activitystreams#Public',
+				get_rest_url_by_path( $path ),
+		);
+	}
+
+	/**
+	 * Transform the WordPress Object into an ActivityPub Object.
+	 *
+	 * @return Activitypub\Activity\Event
+	 */
+	public function to_object() {
+		// Get the corresponding GatherPress Event object.
+		$this->gp_event  = new \GatherPress\Core\Event( $this->wp_object->ID );
+
+		// Initialize the target ActivityPub Event object.
+		$activitypub_object = new \Activitypub\Activity\Extended_Object\Event();
+		$activitypub_object = $this->transform_object_properties( $activitypub_object );
+
+		// Set published and updated.
+		$published = \strtotime( $this->wp_object->post_date_gmt );
+		$activitypub_object->set_published( \gmdate( 'Y-m-d\TH:i:s\Z', $published ) );
+		$updated = \strtotime( $this->wp_object->post_modified_gmt );
+		if ( $updated > $published ) {
+			$activitypub_object->set_updated( \gmdate( 'Y-m-d\TH:i:s\Z', $updated ) );
+		}
+
+		// Also set contentMap via already available content.
+		$activitypub_object->set_content_map(
+			array(
+				$this->get_locale() => $activitypub_object->get_content(),
+			)
+		);
+
+		// Set properties relevant for the event.
+		$activitypub_object->set_comments_enabled( 'open' === $this->wp_object->comment_status ? true : false );
+
+		$activitypub_object->set_external_participation_url( $this->get_url() );
+
+		$online_event_link = $this->gp_event->maybe_get_online_event_link();
+
+		if ( $online_event_link ) {
+			$activitypub_object->set_is_online( true );
+		} else {
+			$activitypub_object->set_is_online( false );
+		}
+
+		$activitypub_object->set_status( 'CONFIRMED' );
+
+		$activitypub_object->set_name( get_the_title( $this->wp_object->ID ) );
+
+		$activitypub_object->set_actor( $this->get_attributed_to() );
+
+		$activitypub_object->set_location();
+		return $activitypub_object;
+	}
+}

includes/core/classes/class-autoloader.php

@@ -45,6 +45,7 @@ static function ( $class_string ): bool {
 				array_unshift( $structure, 'includes' );
 
 				switch ( $class_type ) {
+					case 'activitypub':
 					case 'commands':
 					case 'settings':
 					case 'traits':

includes/core/classes/class-setup.php

@@ -13,6 +13,7 @@
 
 use Exception;
 use GatherPress\Core\Traits\Singleton;
+use GatherPress\Core\ActivityPub\Event_Transformer;
 use WP_Post;
 
 /**
@@ -103,6 +104,7 @@ protected function setup_hooks(): void {
 			array( $this, 'filter_plugin_action_links' )
 		);
 		add_filter( 'load_textdomain_mofile', array( $this, 'load_mofile' ), 10, 2 );
+		add_filter( 'activitypub_transformer', array( $this, 'register_activitypub_transformer' ), 10, 3 );
 	}
 
 	/**
@@ -418,4 +420,24 @@ public function check_users_can_register(): void {
 			);
 		}
 	}
+
+	/**
+	 * Registers a custom event transformer for the ActivityPub plugin.
+	 * 
+	 * The ActivityPub plugin allows to register custom transformers. We want to make sure that 
+	 * GatherPress Events are also properly represented in the ActivityPub world.
+	 * 
+	 * @since 1.0.0
+	 * @see https://github.com/Automattic/wordpress-activitypub/blob/master/includes/transformer/class-factory.php#L37
+	 * 
+	 * @return void
+	 */
+	public function register_activitypub_transformer( $transformer, $wp_object, $object_class ) {
+		if ( 'WP_Post' == $object_class && $wp_object->post_type === 'gp_event' ) {
+			return new Event_Transformer( $wp_object );
+		}
+
+		// Return the default transformer.
+		return $transformer;
+	}
 }