Detect product attributes dynamically

function pm_detect_product_attributes($query, $old_query, $uri_parts, $pm_query, $content_type) {
    global $wpdb, $permalink_manager_uris;

    // Make sure that no custom permalink was detected by Permalink Manager
    if(!empty($pm_query['id'])) {
        return $query;
    }

    // Make sure that $uri_parts variable is set correctly
    if(empty($uri_parts['uri'])) {
        return $query;
    }

    // 1. Parse last two slugs from the requested URI
    preg_match('/(.*)\/([^\/]+)\/([^\/]+)\/?$/', $uri_parts['uri'], $slugs);

    // 2. Check if any of slugs is a product attribute
    if(!empty($slugs[3])) {
        $possible_attributes = array($slugs[2], $slugs[3]);
        $found_attributes = array();

        foreach($possible_attributes as $slug) {
            $sql_query = "SELECT t.slug, t.term_id, tt.taxonomy FROM {$wpdb->terms} AS t INNER JOIN {$wpdb->term_taxonomy} AS tt ON(t.term_id = tt.term_id) WHERE 1=1 AND slug = %s";
        $term = $wpdb->get_row($wpdb->prepare($sql_query, array($slug)));

            if(!empty($term->taxonomy)) {
                $found_attributes[$term->taxonomy] = $term->slug;

                // OPTIONAL. Keep the below line to preselect the attribute in the add-to-cart form
                $_REQUEST["attribute_{$term->taxonomy}"] = $term->slug;
            }
        }

        // 3. Check if the rest of URI is a custom permalink
        $post_id = array_search($slugs[1], $permalink_manager_uris);

        // 3A. Second attempt
        if(empty($post_id)) {
            $post_id = array_search("{$slugs[1]}/$slugs[2]", $permalink_manager_uris);
        }

        // 4. Change the final query if the post (product) is found
        if(!empty($post_id)) {
            $post_object = get_post($post_id);

            if(!empty($post_object->post_type) && $post_object->post_type == 'product') {
                $query = array(
                    'name' => $post_object->post_name,
                    'post_type' => $post_object->post_type,
                    'product' => $post_object->post_name,
                    'do_not_redirect' => 1
                );
            }
        }
    }

    return $query;
}
add_filter('permalink_manager_filter_query', 'pm_detect_product_attributes', 3, 5);