Getting a menu delivered via REST

I am trying to get a menu via REST and I've created a new module and rest resource plugin that allows for GET on /entity/restmenu/{menu_name}.

I can successfully return this example json using this function when I hit the URL.

public function get(EntityInterface $entity) {  $result = array();  for ($i = 0; $i < 10; $i++) {    $temp = array('title' => 'Test ' . $i,'href' => '#/' . $i    );    array_push($result, $temp);  }  return new ResourceResponse(json_encode($result));}

I cannot figure out how to load the menu based on $entity. If I hit my URL (http://dang.dev:8888/entity/restmenu/main?_format=hal_json) $entity's value is 'main' which is the machine name of the main menu.

I've tried using Drupal menu tree, but I am not having luck, and debugging this thing with only JSON responses is quite difficult.

How do I get menu item titles and paths based on the menu machine name?

EDIT

Ok, sort of figured it out.

public function get($entity) {  $menu_name = $entity;  $menu_parameters = \Drupal::menuTree()->getCurrentRouteMenuTreeParameters($menu_name);  $tree = \Drupal::menuTree()->load($menu_name, $menu_parameters);  $renderable = \Drupal::menuTree()->build($tree);  $result = array();  foreach (end($renderable) as $key => $val) {    $temp = array('menu_item' => $val,'route' => $key    );    array_push($result, $temp);  }  return new ResourceResponse(json_encode($result));}

Right now that will output:

[  {"menu_item":{"is_expanded":false,"is_collapsed":false,"in_active_trail":false,"attributes":"","title":"Home","url":{      },"below":[      ],"original_link":{      }    },"route":"standard.front_page"  },  {"menu_item":{"is_expanded":false,"is_collapsed":false,"in_active_trail":false,"attributes":"","title":"Communities","url":{      },"below":[      ],"original_link":{      }    },"route":"menu_link_content:139d0413-dc50-4772-8200-bc6c92571fa7"  }]

any idea why url or original_link are empty?