documentation/Transformers/the-events-calendar-example.md

Folder Structure

You need at least two files. One file for the transformer itself and one file for registering it.

activitypub-tribe-transformer/
|
├─ activitypub/
|  └─ transformer/
|     └─ tribe.php
|
└─ activitypub-tribe-transformer.php

Plugin Files

activitypub-tribe-transformer-php

<?php
/**
 * Plugin Name: ActivityPub Transformer for The Events Calendar
 * Description: Transforms tribe_event posts to ActivityPub object of type Event.
 * Plugin URI:  https://event-federation.eu/
 * Version:     1.0.0
 * Author:      WordPress ActivityPub Enthusiast
 * Author URI:  https://event-federation.eu
 * Text Domain: activitypub-tribe-transformer
 *
    * ActivityPub tested up to: 1.2.0
    */

if ( ! defined( 'ABSPATH' ) ) {
	exit; // Exit if accessed directly.
}

/**
 * Register Tribe Transformer.
 *
 * Include transformer file and register transformer class.
 *
 * @since 1.0.0
 * @param \Activitypub\Transformer\Transformers_Manager $transformers_manager ActivtiyPub transformers manager.
 * @return void
 */
function register_tribe_transformer( $transformers_manager ) {
	require_once( __DIR__ . '/activitypub/transformer/tribe.php' );
	$transformers_manager->register( new \Tribe() );
}

add_action( 'activitypub_transformers_register', 'register_tribe_transformer' );

activtiypub/transformer/tribe.php

<?php
if ( ! defined( 'ABSPATH' ) ) {
	exit; // Exit if accessed directly.
}

/**
 * ActivityPub Tribe Transformer
 *
 * @since 1.0.0
 */
class Tribe extends \Activitypub\Transformer\Base {

	/**
	 * Get widget name.
	 *
	 * Retrieve oEmbed widget name.
	 *
	 * @since 1.0.0
	 * @access public
	 * @return string Widget name.
	 */
	public function get_name() {
		return 'activitypub-tribe/tribe';
	}

	/**
	 * Get widget title.
	 *
	 * Retrieve Transformer title.
	 *
	 * @since 1.0.0
	 * @access public
	 * @return string Widget title.
	 */
	public function get_label() {
		return 'The Events Calendar';
	}

	/**
	 * Returns the ActivityStreams 2.0 Object-Type for an Event.
	 *
	 * @see https://www.w3.org/TR/activitystreams-vocabulary/#dfn-event
	 *
	 * @return string The Event Object-Type.
	 */
	protected function get_object_type() {
		return '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 function get_supported_post_types() {
		return [ 'tribe_events' ];
	}

}