Adding meta values to permalink

Was able to get this working. Thought I would write down what we did in the hopes that it will help someone in the future (or someone can give me feedback on how to better improve it!)

1. Registered Custom Rewrite Rules

   add_action('init', 'pub_rewrite_rules');
   
   function pub_rewrite_rules()
   {
       global $wp_rewrite;
   
       $wp_rewrite->add_rewrite_tag( '%pubyear%', '([0-9]{4})', 'pubyear=");
       $wp_rewrite->add_rewrite_tag( "%pubmonth%', '([0-9]{2})', 'pubmonth=");
   }
   

2. Created Permalink Structure

    function pub_permalink($permalink, $post, $leavename)
    {
        if ( false !== strpos( $permalink, "%publication-type%/%pubyear%/%pubmonth%' ) ) {
   
            $publicationtype = get_the_terms($post->ID, 'publication-type');
            $pubyear = date('Y', get_post_meta($post->ID, 'publication_date', true));
            $pubmonth = date('m', get_post_meta($post->ID, 'publication_date', true));
   
            $rewritecode = array(
                  '%publication-type%',
                  '%pubyear%',
                  '%pubmonth%',
                  $leavename? '' : '%postname%',
            );
   
            $rewritereplace = array(
                  array_pop($publicationtype)->slug,
                  $pubyear,
                  $pubmonth,
                  $post->post_name
            );
   
            $permalink = str_replace($rewritecode, $rewritereplace, $permalink);    
       }
       return $permalink;
   }
   

3. Registered Taxonomy

4. Registered Custom Post Type
   wrote rewrite array to include:

    'slug' => 'publications/%publication-type%/%pubyear%/%pubmonth%',
   

5. flush rewrite rules by going to Permalink Settings page and saving or flush_rewrite_rule()