Wordpress Adjacent Post

/**
 * get previous/next post
 * default WP postnav is limited
 * modified from link below to handle post_type and cats differently
 *
 * @param  string $direction  [which direction to go]
 * @param  string $postTypes [what post types should w]
 * @return [type]             [description]
 */
function my_adjacent_post($direction = 'prev', $inSameTax = false, $tax = null, $postTypes = null, $reverseTax = false)
{
  global $post;

  if(!$postTypes) $postTypes = [$post->post_type];

  $op = ($direction == 'prev' ? 'before' : 'after');
  $order = ($direction == 'prev' ? 'DESC' : 'ASC');

  $args = array(
    'post_type' => $postTypes,
    'showposts' => 1,
    'date_query' => [$op => $post->post_date],
    'orderby' => 'post_date',
    'order' => $order
  );

  if ($inSameTax):
    $topCat = power_top_cat($post->ID, $tax, $reverseTax);

    $args['tax_query'] = array([
			'taxonomy' => $tax,
			'field' => 'id',
			'terms' => $topCat->term_id
		]);
  endif; // limit to taxonomy

  $posts = get_posts($args);

  return empty($posts) ? false : $posts[0];
}