Fast REST Response for Super Admin All Sites Menu (https://github.com/soderlind/super-admin-all-sites-menu), save in mu-plugins

mu-super-admin-all-sites-menu.php

<?php
/**
 * name: Fast REST Response for Super Admin All Sites Menu
 *
 * @package     Soderlind\Multisite\MU
 * @author      Per Soderlind
 * @copyright   2021 Per Soderlind
 * @license     GPL-2.0+
 *
 * @wordpress-plugin
 * Plugin Name: Fast REST Response for Super Admin All Sites Menu
 * Description: Must Use plugin for Super Admin All Sites Menu (https://github.com/soderlind/super-admin-all-sites-menu)
 * Version:     0.0.1
 * Author:      Per Soderlind
 * Author URI:  https://soderlind.no
 * License:     GPL-2.0+
 * License URI: http://www.gnu.org/licenses/gpl-2.0.txt
 */

declare( strict_types = 1 );
namespace Soderlind\Multisite\MU;

if ( ! defined( 'ABSPATH' ) ) {
	wp_die();
}

/**
 * Fires once all must-use and network-activated plugins have loaded.
 *
 */
add_action( 'muplugins_loaded',function() : void {
	$request_uri = parse_url( $_SERVER['REQUEST_URI'], PHP_URL_PATH );
	if ( '/wp-json/super-admin-all-sites-menu/v1/sites/' !== trailingslashit( $request_uri ) ) {
		return;
	}

	$params = json_decode(file_get_contents("php://input"), true); // get HTTP Raw POST data.
	if ( ! is_array( $params ) ) {
		return;
	}
	$offset = ( isset( $params['offset'] ) ) ? filter_var( wp_unslash( $params['offset'] ), FILTER_VALIDATE_INT, [ 'default' => 0 ] ) : 0;

	$mua = new MU_Super_Admin_All_Sites_Menu();
	wp_send_json( $mua->get_sites_menu( $offset ) );

} );	


class MU_Super_Admin_All_Sites_Menu {

	/**
	 * REST load increments.
	 *
	 * @var int
	 */
	private $load_increments;

	/**
	 * Timestamp.
	 *
	 * @var string
	 */
	private $timestamp;

	public function __construct() {
		$this->load_increments = \apply_filters( 'all_sites_menu_load_increments', 100 );
		$this->timestamp = $this->get_timestamp();
	}

	/**
	 * Get menu data.
	 *
	 * @param integer $offset get_sites offset.
	 *
	 * @return array
	 */
	public  function get_sites_menu( int $offset = 0 ) : array {
		$menu      = [];
		$sites     = \get_sites(
			[
				'orderby'  => 'path',
				'number'   => $this->load_increments,
				'offset'   => $offset,
				'deleted'  => '0',
				'mature'   => '0',
				'archived' => '0',
				'spam'     => '0',
			]
		);

		for ( $i = 0; $i < count( $sites ); $i++ ) {

			$blogid   = $sites[$i]->blog_id;
			$blogname = $sites[$i]->__get( 'blogname' );
			$menu_id  = 'blog-' . $blogid;
			$blavatar = '<div class="blavatar"></div>';
			$siteurl  = $sites[$i]->__get( 'siteurl' );
			$adminurl = $siteurl . '/wp-admin';

			if ( ! $blogname ) {
				$blogname = preg_replace( '#^(https?://)?(www.)?#', '', $siteurl );
			}

			// The $site->public value is set to 2, by the Restricted Site Access plugin, when a site has restricted access.
			if ( 2 === (int) $sites[$i]->public ) {
				$blavatar = '<div class="blavatar" style="color:#f00;"></div>';
			}
			$menu[] = [
				'parent'    => 'my-sites-list',
				'id'        => $menu_id,
				'name'      => strtoupper( $blogname ), // Index in local storage.
				'title'     => $blavatar . $blogname,
				'admin'     => $adminurl,
				'url'       => $siteurl,
				'timestamp' => $this->timestamp,
			];
		}

		if ( [] !== $menu ) {
			$response['response'] = 'success';
			$response['data']     = $menu;
		} else {
			$response['response'] = 'unobserve';
			$response['data']     = '';
		}


		return $response;
	}

	/**
	 * Get the timestamp.
	 *
	 * @return string
	 */
	private function get_timestamp() : string {
		$timestamp = get_site_transient( 'allsitemenutimestamp' );
		if ( ! $timestamp ) {
			$timestamp = (string) time();
			set_site_transient( 'allsitemenutimestamp', $timestamp, 3600 );
		}
		return $timestamp;
	}

}