WP_Ajax_Upgrader_Skin example

if ( is_wp_error( $api ) ) {
            if ( str_contains( $api->get_error_message(), 'Plugin not found.' ) ) {
                $api->add_data( array( 'status' => 404 ) );
            } else {
                $api->add_data( array( 'status' => 500 ) );
            }

            return $api;
        }

        $skin     = new WP_Ajax_Upgrader_Skin();
        $upgrader = new Plugin_Upgrader( $skin );

        $result = $upgrader->install( $api->download_link );

        if ( is_wp_error( $result ) ) {
            $result->add_data( array( 'status' => 500 ) );

            return $result;
        }

        // This should be the same as $result above.

array(
            'slug'   => $slug,
            'fields' => array( 'sections' => false ),
        )
    );

    if ( is_wp_error( $api ) ) {
        $status['errorMessage'] = $api->get_error_message();
        wp_send_json_error( $status );
    }

    $skin     = new WP_Ajax_Upgrader_Skin();
    $upgrader = new Theme_Upgrader( $skin );
    $result   = $upgrader->install( $api->download_link );

    if ( defined( 'WP_DEBUG' ) && WP_DEBUG ) {
        $status['debug'] = $skin->get_upgrade_messages();
    }

    if ( is_wp_error( $result ) ) {
        $status['errorCode']    = $result->get_error_code();
        $status['errorMessage'] = $result->get_error_message();
        wp_send_json_error( $status );
    }