<?php
// include('formats.php');

class Make_Sticky_Endpoint extends WP_REST_Controller {
    /**
     * Register the routes for the objects of the controller.
     */
    public function register_custom_route($route) {
        $version = '2';
        $namespace = 'craft/v' . $version;

        register_rest_route( $namespace, '/' . $route, [
            array(
                'methods'  => WP_REST_Server::READABLE,
                'callback' => array( $this, 'get_all_items' )
            ),
        ]);
    }
    public function get_all_items( $request ) {
        $args = array(
            'numberposts' => 20,
            'post_type' => [
                'artist',
                'episode',
                'event',
                'exhibition',
                'guide',
                'object',
                'publication',
                'technique',
                'short',
                'post',
                'page'
            ],
            'meta_query' => [array(
                'key' => 'is_sticky',
                'value' => 'on',
                'compare' => 'LIKE'
            )]
        );

        return new WP_REST_Response( $this->prepare_all_items_for_response($args), 200 );
    }
    public function prepare_all_items_for_response( $args ) {
        $collection = array();
        
        // https://developer.wordpress.org/reference/functions/get_posts/
        foreach( get_posts($args) as $item ) {
            $collection[$item->ID] = default_post_format( $item, true );
        }
        wp_reset_postdata();

        return $collection;
    }
}

?>