FP

fp_nav.php

<?php
  defined('ABSPATH') || exit;

  class _FP_Nav {

    public static $nav = false;
    public static $instance = null;

    function __construct() {
      self::$instance = $this;
      $this->generate_nav_tree();
    }

    public function get_nav_tree() {
      return self::$nav;
    }

    public function search_nav_tree($slug, $tree) {
      if (!$tree) {
        $tree = self::$nav;
      } else if (isset($tree->child_items)) {
        $tree = $tree->child_items;
      }

      foreach ($tree as $key => $node) {
        $node_slug = $node->object == 'custom' ? $node->post_name : get_post_field('post_name', $node->object_id);

        if ($node_slug == $slug) {
          return $node;
        }
      }
      return false;
    }

    public function generate_nav_tree() {
      self::$nav = $this->nav_to_tree();
    }

    public function nav_to_tree() {
      $nav_items = wp_get_nav_menu_items( 'main', array( 'update_post_term_cache' => false ) );

      // wordpress does not group child nav items with parent nav items
      $child_items = [];
      // pull all child nav items into separate object
      foreach ($nav_items as $key => $item) {
        if ($item->menu_item_parent) {
          array_push($child_items, $item);
          unset($nav_items[$key]);
        }
      }

      // push child items into their parent item in the original object
      // May repeat the loop if a child is found before the parent
      while (count($child_items)) {
        foreach ($child_items as $key => $child_item) {
          if ($this->nav_push_parent($nav_items, $child_item)) {
            unset($child_items[$key]);
          }
        }
      }

      return array_values($nav_items);
    }

    public function nav_push_parent(&$parents, $child) {
      foreach ($parents as $key => $item) {
        if ($child->menu_item_parent == $item->ID) {
          if (!$item->child_items) {
            $item->child_items = [];
          }
          array_push($item->child_items, $child);
          return true;
        }

        if ($item->child_items) {
          if ($this->nav_push_parent($item->child_items, $child)) {
            return true;
          }
        }
      }

      return false;
    }
  }

  function FP_Nav() {
    if (!(_FP_Nav::$instance)) {
      return new _FP_Nav();
    } else {
      return _FP_Nav::$instance;
    }
  }

fp_router.php

<?php
  defined('ABSPATH') || exit;

  class _FP_Router {

    public static $instance = null;
    public static $route = null;

    function __construct() {
      self::$instance = $this;

      add_action('do_parse_request', array($this, 'do_parse_request'), 10, 2);
    }

    public function get_current_route() {
      return self::$route;
    }

    public function do_parse_request($do, $wp) {
      global $wp_query;

      $path = trim(parse_url(esc_url_raw(add_query_arg([])), PHP_URL_PATH), '/');
      $home_path = trim(parse_url(esc_url_raw(home_url()), PHP_URL_PATH), '/');
      $home_path and $path = trim(substr($path, strlen($home_path)), '/');

      $found = true;
      $path = explode('/', $path);

      if (!empty($path)) {
        $prev_node = null;
        $node = null;
        foreach ($path as $path_item) {
          $node = FP_Nav()->search_nav_tree($path_item, $node);
          if ($node->object != 'custom') {
            $node = $prev_node;
            $found = true;
            break;
          }
          if (!$node) {
            $found = false;
            break;
          }
          $prev_node = $node;
        }
        self::$route = $node;
      }

      if ($found) {
        // If found, set the pagename to home for the correct behavior of wp
        $wp->query_vars['pagename'] = 'home';
        $do = false;
      }

      return $do;
    }
  }

  function FP_Router() {
    if (!(_FP_Router::$instance)) {
      return new _FP_Router();
    } else {
      return _FP_Router::$instance;
    }
  }

functions.php

<?php

/*
	Require every files from ./inc/
*/
foreach (glob(__DIR__ . "/inc/*") as $filename) {
  if (!is_dir($filename)) {
    require_once($filename);
  }
}
add_theme_support( 'post-thumbnails' );

FP_Nav();
FP_Router();