WIP: Rewrite of transformer management

includes/activity/class-base-object.php

@@ -26,6 +26,9 @@ use function Activitypub\snake_to_camel_case;
  * @see https://www.w3.org/TR/activitystreams-core/#object
  */
 class Base_Object {
+	const CONTEXT_ACTIVITYSTREAMS = 'https://www.w3.org/ns/activitystreams';
+	const CONTEXT_SECURITY = 'https://w3id.org/security/v1';
+
 	/**
 	 * The object's unique global identifier
 	 *
@@ -457,7 +460,7 @@ class Base_Object {
 		}
 
 		if ( \strncasecmp( $method, 'set', 3 ) === 0 ) {
-			$this->set( $var, $params[0] );
+			return $this->set( $var, $params[0] );
 		}
 
 		if ( \strncasecmp( $method, 'add', 3 ) === 0 ) {
@@ -465,6 +468,13 @@ class Base_Object {
 		}
 	}
 
+	/**
+	 * The ActivityPub object typicallly can define it's own JSON-LD context.
+	 */
+	public function __construct() {
+		$this->context = $this->get_context();
+	}
+
 	/**
 	 * Magic function, to transform the object to string.
 	 *
@@ -506,6 +516,9 @@ class Base_Object {
 	 * @return boolean True if the object has the key.
 	 */
 	public function has( $key ) {		
+		if ( $key === 'actor ') {
+			$key = 'actor';
+		}
 		return property_exists( $this, $key );
 	}
 
@@ -519,12 +532,16 @@ class Base_Object {
 	 */
 	public function set( $key, $value ) {
 		if ( ! $this->has( $key ) ) {
+			if ( $key === 'actor' ) {
+				$key = 'actor';
+			}
 			return new WP_Error( 'invalid_key', __( 'Invalid key', 'activitypub' ), array( 'status' => 404 ) );
 		}
 
+
 		$this->$key = $value;
 
-		return $this->$key;
+		return $this;
 	}
 
 	/**
@@ -692,4 +709,110 @@ class Base_Object {
 	public function get_object_var_keys() {
 		return \array_keys( \get_object_vars( $this ) );
 	}
+
+	/**
+	 * Get the context information for a property.
+	 *
+	 * @param string $property
+	 *
+	 * @return array|null
+	 */
+	private function get_property_context( string $property ) {
+		$reflection_class = new \ReflectionClass( $this );
+
+		if ( $reflection_class->hasProperty( $property ) ) {
+			$reflection_property = $reflection_class->getProperty( $property );
+			$doc_omment = $reflection_property->getDocComment();
+
+			// Extract context information from the doc comment.
+			preg_match( '/@context\s+([^\s]+)/', $doc_omment, $matches );
+
+			if ( ! empty( $matches[1] ) ) {
+				return $matches[1];
+			} else {
+				return self::CONTEXT_ACTIVITYSTREAMS;
+			}
+		}
+
+		return null;
+	}
+
+	/**
+	 * Compact the context via the JSON-LD syntax.
+	 * 
+	 * @param array $key_context A certain part of the whole context.
+	 * @param array $array The full URIs of the contexts.
+	 * @param array $abbreviation The short name of the context.
+	 * 
+	 * @return array $key_kontext The compacted context.
+	 */
+	private static function compact_context( $key_context, $namespace, $abbreviation ) {
+		$abbreviation_added = false;
+		foreach ( $key_context as $key => $value ) {
+			// Check if the key starts with the namespace
+			if ( strpos( $value, $namespace ) === 0 ) {
+				// Replace the key
+				$key_context[ $key ] = $abbreviation . ':' . substr( $value, strlen( $namespace ) );
+
+				// Add abbreviation element for the namespace only once
+				if ( ! $abbreviation_added ) {
+					$key_context = array( $abbreviation => $namespace ) + $key_context;
+					$abbreviation_added = true;
+				}
+			}
+		}
+		return $key_context;
+	}
+
+	/**
+	 * Builds the context of the ActivityPub object via the PHP docs.
+	 * 
+	 * @return array $context A shortened and clean JSON-LD context for the ActivityPub object.
+	 */
+	public static function get_context() {
+		$class = static::class;
+
+		// Try to lookup the context from a transient.
+		$transient = "activitypub_json_context_object_{$class}";
+		$context = get_transient( $transient );
+		if ( $context ) {
+			return $context;
+		}
+		$reflection_class = new \ReflectionClass( static::class );
+		$context = array(
+			self::CONTEXT_ACTIVITYSTREAMS,
+			self::CONTEXT_SECURITY,
+		);
+
+		$key_context = array();
+
+		foreach ( $reflection_class->getProperties() as $property ) {
+			$doc_omment = $property->getDocComment();
+
+			// Extract context information from the doc comment.
+			preg_match( '/@context\s+([^\s]+)/', $doc_omment, $matches );
+
+			if ( ! empty( $matches[1] ) ) {
+				$key_context[ snake_to_camel_case( $property->name ) ] = $matches[1];
+			}
+		}
+
+		$namespace_abbreviations = array(
+			'https://joinpeertube.org/ns#'        => 'pt',
+			'https://joinmobilizon.org/ns#'       => 'mz',
+			'https://schema.org/'                 => 'sc',
+			'https://www.w3.org/2002/12/cal/ical#' => 'ical',
+		);
+
+		foreach ( $namespace_abbreviations as $namespace => $abbreviation ) {
+			$key_context = self::compact_context( $key_context, $namespace, $abbreviation );
+		}
+
+		if ( ! empty( $key_context ) ) {
+			$context[] = $key_context;
+		}
+
+		set_transient( $transient, $context );
+		return $context;
+	}
 }

includes/activity/class-event.php

@@ -0,0 +1,128 @@
+<?php
+/**
+ * ActivityPub Object of type Event.
+ *
+ * @package activity-event-transformers
+ * @license AGPL-3.0-or-later
+ */
+
+namespace Activitypub\Activity;
+
+use Activitypub\Activity\Base_Object;
+
+use function Activitypub\snake_to_camel_case;
+
+/**
+ * Event is an implementation of one of the Activity Streams Event object type.
+ *
+ * This class contains extra keys as used by Mobilizon to ensure compatibility.
+ *
+ * @see https://www.w3.org/TR/activitystreams-vocabulary/#dfn-event
+ */
+class Event extends Base_Object {
+	// todo maybe rename to mobilizon event?
+	const REPLIES_MODERATION_OPTION_TYPES = array( 'allow_all', 'closed' );
+	const JOIN_MODE_TYPES = array( 'free', 'restricted', 'external' ); // amd 'invite', but not used by mobilizon atm
+	const ICAL_EVENT_STATUS_TYPES = array( 'TENTATIVE', 'CONFIRMED', 'CANCELLED' );
+
+	/**
+	 * Event is an implementation of one of the
+	 * Activity Streams
+	 *
+	 * @var string
+	 */
+	protected $type = 'Event';
+
+	protected $name;
+
+	protected $contacts;
+
+	/**
+	 * Extension invented by PeerTube whether comments/replies are <enabled>
+	 * Mobilizon also implemented this as a fallback to their own
+	 * repliesModerationOption.
+	 *
+	 * @context https://joinpeertube.org/ns#commentsEnabled
+	 * @see https://docs.joinpeertube.org/api/activitypub#video
+	 * @see https://docs.joinmobilizon.org/contribute/activity_pub/
+	 * @var bool|null
+	 */
+	protected $comments_enabled;
+
+	/**
+	 * @context https://joinmobilizon.org/ns#timezone
+	 * @var string
+	 */
+	protected $timezone;
+
+	/**
+	 * @context https://joinmobilizon.org/ns#repliesModerationOption
+	 * @see https://docs.joinmobilizon.org/contribute/activity_pub/#repliesmoderation
+	 * @var string
+	 */
+	protected $replies_moderation_option;
+
+	/**
+	 * @context https://joinmobilizon.org/ns#anonymousParticipationEnabled
+	 * @see https://docs.joinmobilizon.org/contribute/activity_pub/#anonymousparticipationenabled
+	 * @var bool
+	 */
+	protected $anonymous_participation_enabled;
+
+	/**
+	 * @context https://schema.org/category
+	 * @var enum
+	 */
+	protected $category;
+
+	/**
+	 * @context https://schema.org/inLanguage
+	 * @var
+	 */
+	protected $in_language;
+
+	/**
+	 * @context https://joinmobilizon.org/ns#isOnline
+	 * @var bool
+	 */
+	protected $is_online;
+
+	/**
+	 * @context https://www.w3.org/2002/12/cal/ical#status
+	 * @var enum
+	 */
+	protected $status;
+
+	/**
+	 * @context https://joinmobilizon.org/ns#externalParticipationUrl
+	 * @var string
+	 */
+	protected $external_participation_url;
+
+	/**
+	 * @context https://joinmobilizon.org/ns#joinMode
+	 * @see https://docs.joinmobilizon.org/contribute/activity_pub/#joinmode
+	 * @var
+	 */
+	protected $join_mode;
+
+	/**
+	 * @context https://joinmobilizon.org/ns#participantCount
+	 * @var int
+	 */
+	protected $participant_count;
+
+	/**
+	 * @context https://schema.org/maximumAttendeeCapacity
+	 * @see https://docs.joinmobilizon.org/contribute/activity_pub/#maximumattendeecapacity
+	 * @var int
+	 */
+	protected $maximum_attendee_capacity;
+
+	/**
+	 * @context https://schema.org/remainingAttendeeCapacity
+	 * @see https://docs.joinmobilizon.org/contribute/activity_pub/#remainignattendeecapacity
+	 * @var int
+	 */
+	protected $remaining_attendee_capacity;
+}

includes/activity/class-place.php

@@ -0,0 +1,94 @@
+<?php
+/**
+ * Event is an implementation of one of the
+ * Activity Streams Event object type
+ *
+ * @package activity-event-transformers
+ * @license AGPL-3.0-or-later
+ */
+
+namespace Activitypub\Activity;
+
+use Activitypub\Activity\Base_Object;
+
+/**
+ * Event is an implementation of one of the
+ * Activity Streams Event object type
+ *
+ * The Object is the primary base type for the Activity Streams
+ * vocabulary.
+ *
+ * @see https://www.w3.org/TR/activitystreams-vocabulary/#dfn-event
+ */
+class Place extends Base_Object {
+	/**
+	 * Place is an implementation of one of the
+	 * Activity Streams
+	 *
+	 * @var string
+	 */
+	protected $type = 'Place';
+
+	/**
+	 * Indicates the accuracy of position coordinates on a Place objects.
+	 * Expressed in properties of percentage. e.g. "94.0" means "94.0% accurate".
+	 *
+	 * @see https://www.w3.org/TR/activitystreams-vocabulary/#dfn-accuracy
+	 * @var float xsd:float [>= 0.0f, <= 100.0f]
+	 */
+	protected $accuracy;
+
+	/**
+	 * Indicates the altitude of a place. The measurement units is indicated using the units property.
+	 * If units is not specified, the default is assumed to be "m" indicating meters.
+	 *
+	 * @see https://www.w3.org/TR/activitystreams-vocabulary/#dfn-altitude
+	 * @var float xsd:float
+	 */
+	protected $altitude;
+
+	/**
+	 * The latitude of a place.
+	 *
+	 * @see https://www.w3.org/TR/activitystreams-vocabulary/#dfn-latitude
+	 * @var float xsd:float
+	 */
+	protected $latitude;
+
+	/**
+	 * The longitude of a place.
+	 *
+	 * @see https://www.w3.org/TR/activitystreams-vocabulary/#dfn-longitude
+	 * @var float xsd:float
+	 */
+	protected $longitude;
+
+	/**
+	 * @see https://www.w3.org/TR/activitystreams-vocabulary/#dfn-radius
+	 * @var float
+	 */
+	protected $radius;
+
+	/**
+	 * @see https://www.w3.org/TR/activitystreams-vocabulary/#dfn-units
+	 * @var string
+	 */
+	protected $units;
+
+	/**
+	 * Extension invented by PeerTube whether comments/replies are <enabled>
+	 * Mobilizon also implemented this as a fallback to their own
+	 * repliesModerationOption.
+	 *
+	 * @see https://docs.joinpeertube.org/api/activitypub#video
+	 * @see https://docs.joinmobilizon.org/contribute/activity_pub/
+	 *
+	 * @var bool
+	 */
+	protected $comments_enabled;
+
+	/**
+	 * @var Postal_Address|string
+	 */
+	protected $address;
+}

includes/activity/class-postal-address.php

@@ -0,0 +1,62 @@
+<?php
+/**
+ * PostalAddress is a custom ActivityPub object firstly used by Mobilizon
+ * derived from https://schema.org/PostalAddress.
+ *
+ * @package activity-event-transformers
+ * @license AGPL-3.0-or-later
+ */
+
+namespace Activitypub\Activity;
+
+use Activitypub\Activity\Base_Object;
+
+/**
+ * @see https://www.w3.org/TR/activitystreams-vocabulary/#dfn-event
+ */
+class Postal_Address extends Base_Object {
+	/**
+	 * Place is an implementation of one of the
+	 * Activity Streams
+	 *
+	 * @var string
+	 */
+	protected $type = 'PostalAddress';
+
+	/**
+	 * The country. For example, USA. You can also provide the two-letter ISO 3166-1 alpha-2 country code.
+	 *
+	 * @see http://en.wikipedia.org/wiki/ISO_3166-1
+	 * @var string
+	 */
+	protected $address_country;
+
+	/**
+	 * The locality in which the street address is, and which is in the region. For example, Mountain View.
+	 *
+	 * @var string
+	 */
+	protected $address_locality;
+
+	/**
+	 * The region in which the locality is, and which is in the country.
+	 * For example, California or another appropriate first-level Administrative division.
+	 *
+	 * @var string
+	 */
+	protected $address_region;
+
+	/**
+	 * The postal code. For example, 94043.
+	 *
+	 * @var string
+	 */
+	protected $postal_code;
+
+	/**
+	 * The street address. For example, 1600 Amphitheatre Pkwy.
+	 *
+	 * @var string
+	 */
+	protected $street_address;
+}

includes/class-activity-dispatcher.php

@@ -62,7 +62,7 @@ class Activity_Dispatcher {
 	 * @return void
 	 */
 	public static function send_activity( $wp_object, $type, $user_id = null ) {
-		$transformer = Factory::get_transformer( $wp_object );
+		$transformer = Factory::instance()->get_transformer( $wp_object );
 
 		if ( null !== $user_id ) {
 			$transformer->change_wp_user_id( $user_id );
@@ -106,7 +106,7 @@ class Activity_Dispatcher {
 			return;
 		}
 
-		$transformer = Factory::get_transformer( $wp_object );
+		$transformer = Factory::instance()->get_transformer( $wp_object );
 		$transformer->change_wp_user_id( Users::BLOG_USER_ID );
 
 		$user_id  = $transformer->get_wp_user_id();

includes/class-migration.php

@@ -197,4 +197,20 @@ class Migration {
 			wp_cache_delete( sprintf( Followers::CACHE_KEY_INBOXES, $user_id ), 'activitypub' );
 		}
 	}
+
+	/**
+	 * Updates the supported post type settings to the mapped transformer setting.
+	 * TODO: Test this
+	 * @return void
+	 */
+	private static function migrate_from_version_number_transformer_management_placeholder() {
+		$supported_post_types = \get_option( 'activitypub_support_post_types', array( 'post', 'page' ) );
+		Admin::register_settings();
+		$transformer_mapping = array();
+		foreach ( $supported_post_types as $supported_post_type ) {
+			$transformer_mapping[ $supported_post_type ] = 'activitypub/post';
+		}
+		update_option( 'activitypub_transformer_mapping', $transformer_mapping );
+	}
+
 }

includes/transformer/class-attachment.php

@@ -14,6 +14,24 @@ use Activitypub\Transformer\Post;
  * - Activitypub\Activity\Base_Object
  */
 class Attachment extends Post {
+	/**
+	 * Getter function for the name of the transformer.
+	 *
+	 * @return string name
+	 */
+	public function get_name() {
+		return 'activitypub/attachment';
+	}
+
+	/**
+	 * Getter function for the display name (label/title) of the transformer.
+	 *
+	 * @return string name
+	 */
+	public function get_label() {
+		return 'Built-In Transformer for WordPress Attachments';
+	}
+
 	/**
 	 * Generates all Media Attachments for a Post.
 	 *

includes/transformer/class-base.php

@@ -18,6 +18,8 @@ abstract class Base {
 	 */
 	protected $object;
 
+	protected $activitypub_object_type = 'Base_Object';
+
 	/**
 	 * Static function to Transform a WordPress Object.
 	 *
@@ -36,8 +38,10 @@ abstract class Base {
 	 *
 	 * @param stdClass $object
 	 */
-	public function __construct( $object ) {
-		$this->object = $object;
+	public function __construct( $object=null ) {
+		if  ( $object ) {
+			$this->object = $object;
+		}
 	}
 
 	/**
@@ -102,4 +106,30 @@ abstract class Base {
 	 * @return int The User-ID of the WordPress Post
 	 */
 	abstract public function change_wp_user_id( $user_id );
+
+	/**
+	 * Get the name used for registering the transformer with the ActivityPub plugin.
+	 *
+	 * @since version_number_transformer_management_placeholder
+	 * @return string name
+	 */
+	abstract public function get_name();
+
+	/**
+	 * Get the display name for the ActivityPub transformer.
+	 *
+	 * @since version_number_transformer_management_placeholder
+	 * @return string display name
+	 */
+	abstract public function get_label();
+
+	/**
+	 * Returns the ActivityStreams 2.0 Object-Type for a Post.
+	 *
+	 * @see https://www.w3.org/TR/activitystreams-vocabulary/#activity-types
+	 *
+	 * @return string The Object-Type.
+	 */
+	abstract protected function get_object_type();
+
 }

includes/transformer/class-factory.php

@@ -9,7 +9,214 @@ use Activitypub\Transformer\Attachment;
  * Transformer Factory
  */
 class Factory {
-	public static function get_transformer( $object ) {
+	const DEFAULT_TRANSFORMER_MAPPING = array(
+		'post' => 'activitypub/post',
+		'page' => 'activitypub/post',
+		'attachment' => 'activitypub/attachment',
+	);
+
+	/**
+	 * Transformers.
+	 *
+	 * Holds the list of all the ActivityPub transformers. Default is `null`.
+	 *
+	 * @since version_number_transformer_management_placeholder
+	 * @access private
+	 *
+	 * @var \ActivityPub\Transformer\Base[]
+	 */
+	private $transformers = null;
+
+	/**
+	 * F instance.
+	 *
+	 * Holds the transformer instance.
+	 *
+	 * @since version_number_transformer_management_placeholder
+	 * @access protected
+	 */
+	protected static $_instances = [];
+
+
+	/**
+	 * Instance.
+	 *
+	 * Ensures only one instance of the transformer manager class is loaded or can be loaded.
+	 *
+	 * @since version_number_transformer_management_placeholder
+	 * @access public
+	 * @static
+	 *
+	 * @return Transformer_Manager An instance of the class.
+	 */
+	public static function instance() {
+		$class_name = static::class_name();
+
+		if ( empty( static::$_instances[ $class_name ] ) ) {
+			static::$_instances[ $class_name ] = new static();
+		}
+
+		return static::$_instances[ $class_name ];
+	}
+
+	/**
+	 * Class name.
+	 *
+	 * Retrieve the name of the class.
+	 *
+	 * @since version_number_transformer_management_placeholder
+	 * @access public
+	 * @static
+	 */
+	public static function class_name() {
+		return get_called_class();
+	}
+
+	/**
+	 * Checks if a transformer is registered.
+	 *
+	 * @since version_number_transformer_management_placeholder
+	 *
+	 * @param string $name Transformer name including namespace.
+	 * @return bool True if the block type is registered, false otherwise.
+	 */
+	public function is_registered( $name ) {
+		return isset( $this->transformers[ $name ] );
+	}
+
+	/**
+	 * Register a transformer.
+	 *
+	 * @since version_number_transformer_management_placeholder
+	 * @access public
+	 *
+	 * @param \ActivityPub\Transformer\Base $transformer_instance ActivityPub Transformer.
+	 *
+	 * @return bool True if the ActivityPub transformer was registered.
+	 */
+	public function register( \ActivityPub\Transformer\Base $transformer_instance ) {
+
+		if ( ! $transformer_instance instanceof \ActivityPub\Transformer\Base ) {
+			_doing_it_wrong(
+				__METHOD__,
+				\esc_html__( 'ActivityPub transformer instance must be a of \ActivityPub\Transformer_Base class.' ),
+				'version_number_transformer_management_placeholder'
+			);
+			return false;
+		}
+
+		$transformer_name = $transformer_instance->get_name();
+		if ( preg_match( '/[A-Z]+/', $transformer_name ) ) {
+			_doing_it_wrong(
+				__METHOD__,
+				\esc_html__( 'ActivityPub transformer names must not contain uppercase characters.' ),
+				'version_number_transformer_management_placeholder'
+			);
+			return false;
+		}
+
+		$name_matcher = '/^[a-z0-9-]+\/[a-z0-9-]+$/';
+		if ( ! preg_match( $name_matcher, $transformer_name ) ) {
+			_doing_it_wrong(
+				__METHOD__,
+				\esc_html__( 'ActivityPub transformer names must contain a namespace prefix. Example: my-plugin/my-custom-transformer' ),
+				'version_number_transformer_management_placeholder'
+			);
+			return false;
+		}
+
+		if ( $this->is_registered( $transformer_name ) ) {
+			_doing_it_wrong(
+				__METHOD__,
+				/* translators: %s: Block name. */
+				sprintf( 'ActivityPub transformer with name "%s" is already registered.', esc_html( $transformer_name ) ),
+				'version_number_transformer_management_placeholder'
+			);
+			return false;
+		}
+
+		/**
+		 * Should the ActivityPub transformer be registered.
+		 *
+		 * @since version_number_transformer_management_placeholder
+		 *
+		 * @param bool $should_register Should the ActivityPub transformer be registered. Default is `true`.
+		 * @param \ActivityPub\Transformer\Base $transformer_instance Widget instance.
+		 */
+		$should_register = apply_filters( 'activitypub_transformer_is_enabled', true, $transformer_instance );
+
+		if ( ! $should_register ) {
+			return false;
+		}
+
+		$this->transformers[ $transformer_name ] = $transformer_instance;
+
+		return true;
+	}
+
+	/**
+	 * Init transformers.
+	 *
+	 * Initialize ActivityPub transformer manager.
+	 * Include the builtin transformers by default and add third party ones.
+	 *
+	 * @since version_number_transformer_management_placeholder
+	 * @access private
+	 */
+	private function init_transformers() {
+		$builtin_transformers = [
+			'post',
+			'attachment'
+		];
+
+		$this->transformers = [];
+
+		foreach ( $builtin_transformers as $transformer_name ) {
+			$class_name = ucfirst( $transformer_name );
+
+			$class_name = '\Activitypub\Transformer\\' . $class_name;
+
+			$this->register( new $class_name() );
+		}
+
+		/**
+		 * Let other transformers register.
+		 *
+		 * Fires after the built-in Activitypub transformers are registered.
+		 *
+		 * @since version_number_transformer_management_placeholder
+		 *
+		 * @param Transformer_Factory $this The widgets manager.
+		 */
+		do_action( 'activitypub_transformers_register', $this );
+	}
+
+	/**
+	 * Get available ActivityPub transformers.
+	 *
+	 * Retrieve the registered transformers list. If given a transformer name
+	 * it returns the given transformer if it is registered.
+	 *
+	 * @since version_number_transformer_management_placeholder
+	 * @access public
+	 *
+	 * @param string $transformer_name Optional. Transformer name. Default is null.
+	 *
+	 * @return Base|Base[]|null Registered transformers.
+	 */
+	public function get_transformer_class( $transformer_name = null ) {
+		if ( is_null( $this->transformers ) ) {
+			$this->init_transformers();
+		}
+
+		if ( null !== $transformer_name ) {
+			return isset( $this->transformers[ $transformer_name ] ) ? $this->transformers[ $transformer_name ] : null;
+		}
+
+		return $this->transformers;
+	}
+
+	public static function get_default_transformer( $object ) {
 		/**
 		 * Filter the transformer for a given object.
 		 *
@@ -58,4 +265,40 @@ class Factory {
 				return null;
 		}
 	}
+
+	/**
+	 * Get the mapped ActivityPub transformer.
+	 *
+	 * Returns a new instance of the needed WordPress to ActivityPub transformer.
+	 *
+	 * @since version_number_transformer_management_placeholder
+	 * @access public
+	 *
+	 * @param WP_Post|WP_Comment $object The WordPress Post/Comment.
+	 *
+	 * @return \ActivityPub\Transformer\Base|null Registered transformers.
+	 */
+	public function get_transformer( $object ) {
+		switch ( get_class( $object ) ) {
+			case 'WP_Post':
+				$post_type = get_post_type( $object );
+				$transformer_mapping = \get_option( 'activitypub_transformer_mapping', self::DEFAULT_TRANSFORMER_MAPPING );
+				$transformer_name = $transformer_mapping[ $post_type ];
+				if ( $transformer_name ) {
+					$transformer_class =  $this->get_transformer_class( $transformer_name );
+				} else {
+					return self::get_default_transformer( $object );
+				}
+	
+				if ( $transformer_class ) {
+					return new $transformer_class( $object );
+				} else {
+					return self::get_default_transformer( $object );
+				}
+			case 'WP_Comment':
+				return new Comment( $object );
+			default:
+			   self::get_default_transformer( $object );
+		}
+	}
 }

includes/transformer/class-post.php

@@ -24,6 +24,24 @@ use function Activitypub\site_supports_blocks;
  * - Activitypub\Activity\Base_Object
  */
 class Post extends Base {
+	/**
+	 * Getter function for the name of the transformer.
+	 *
+	 * @return string name
+	 */
+	public function get_name() {
+		return 'activitypub/post';
+	}
+
+	/**
+	 * Getter function for the display name (label/title) of the transformer.
+	 *
+	 * @return string name
+	 */
+	public function get_label() {
+		return 'Built-In Transformer for WordPress Posts';
+	}
+
 	/**
 	 * Returns the ID of the WordPress Post.
 	 *

templates/comment-json.php

@@ -1,7 +1,7 @@
 <?php
 $comment = \get_comment( \get_query_var( 'c', null ) ); // phpcs:ignore
 
-$object = \Activitypub\Transformer\Factory::get_transformer( $comment );
+$object = \Activitypub\Transformer\Factory::instance()->get_transformer( $comment );
 $json = \array_merge( array( '@context' => \Activitypub\get_context() ), $object->to_object()->to_array() );
 
 // filter output

templates/post-json.php

@@ -2,8 +2,7 @@
 // phpcs:ignore WordPress.WP.GlobalVariablesOverride.Prohibited
 $post = \get_post();
 
-$post_object = \Activitypub\Transformer\Factory::get_transformer( $post )->to_object();
-$post_object->set_context( \Activitypub\get_context() );
+$post_object = \Activitypub\Transformer\Factory::instance()->get_transformer( $post )->to_object();
 
 /*
  * Action triggerd prior to the ActivityPub profile being created and sent to the client