WP Votes counter using rest api

votes_counter.php

<?php
/*
Update post meta based on the action taken on the post
*/
function mubit_update_votes($id, $key, $action) {
  $data = array();
  if(empty($id) || empty($action) || empty($key)) {
    return $data;
  }
  $votes = get_post_meta($id, $key, true);
  if(empty($votes)) {
    update_post_meta($id, $key, 1);
    $data[$action] = 1;
  } else {
    $votes = intval($votes) + 1;
    update_post_meta($id, $key, $votes);
    $data[$action] = $votes;
  }
  return $data;
}

/*
Votes Callback
Verifying the nonce passed in the post boday `mu`
*/
function mubit_votes_post_cb( $request ) {
  $data = array();
  $params = $request->get_params();
  $nonce_verify = wp_verify_nonce( $params['mu'], 'wp_rest' );
  if(!$nonce_verify) {
    return new WP_Error( 'code', __( 'Request origin error.', 'nysw' ) );
  }
  $id = $params['id'];
  $action = $params['action'];
  if(isset($params) && isset($id) && intval($id)
  && isset($action) && !empty($action)) {
    $id = intval($id);
    if($action === 'upvotes'){
      $data = mubit_update_votes($id, '_bk_upvote_count', $action);
    } elseif($action === 'downvotes'){
      $data = mubit_update_votes($id, '_bk_downvote_count', $action);
    }
    $res = wp_send_json($data);
    return new WP_REST_Response( $res, 200 );
  } else {
    return new WP_Error( 'code', __( 'Error performing an action.', 'nysw' ) );
  }
  return null;
}

/*
Adds a custom route `mubit/v1` with one endpoint `votes`
*/
function mubit_custom_route() {
  register_rest_route( 'mubit/v1', '/votes/(?P<id>\d+)',
     array(
      'methods' => WP_REST_Server::CREATABLE,
      'callback' => 'mubit_votes_post_cb',
     )
 );
}
add_action( 'rest_api_init', 'mubit_custom_route');