Draft: Issue #3447727: Add JSON API Menu Tree submodule with resource for hierarchical menu structure

modules/jsonapi_menu_items_tree/src/Resource/MenuTreeResource.php

+<?php
+
+namespace Drupal\jsonapi_menu_items_tree\Resource;
+
+use Drupal\Core\Access\AccessResultInterface;
+use Drupal\Core\Cache\CacheableMetadata;
+use Drupal\Core\GeneratedUrl;
+use Drupal\jsonapi\JsonApiResource\LinkCollection;
+use Drupal\jsonapi\JsonApiResource\ResourceObject;
+use Drupal\system\MenuInterface;
+use Drupal\jsonapi_menu_items\Resource\MenuItemsResource;
+
+/**
+ * Processes a request for a menu and delivers a processed menu tree structure.
+ *
+ * @internal
+ */
+class MenuTreeResource extends MenuItemsResource {
+
+  /**
+   * Overrides the parent method to provide a custom menu tree structure.
+   *
+   * @param \Drupal\Core\Menu\MenuLinkTreeElement[] $tree
+   *   The menu tree.
+   * @param array $items
+   *   The already created items.
+   * @param \Drupal\Core\Cache\CacheableMetadata $cache
+   *   The cacheable metadata.
+   * @param \Drupal\system\MenuInterface $menu
+   *   The menu that the links belong to.
+   */
+  protected function getMenuItems(array $tree, array &$items, CacheableMetadata $cache, MenuInterface $menu) {
+    $items = [];
+    foreach ($tree as $menu_link) {
+
+      if ($menu_link->access !== NULL && !$menu_link->access instanceof AccessResultInterface) {
+        throw new \DomainException('MenuLinkTreeElement::access must be either NULL or an AccessResultInterface object.');
+      }
+
+      if ($menu_link->access instanceof AccessResultInterface) {
+        $cache->merge(CacheableMetadata::createFromObject($menu_link->access));
+      }
+
+      // Only return accessible links.
+      if ($menu_link->access instanceof AccessResultInterface && !$menu_link->access->isAllowed()) {
+        continue;
+      }
+
+      $id = $menu_link->link->getPluginId();
+      [$plugin] = explode(':', $id, 2);
+      if ($plugin === 'menu_link_config') {
+        $resource_type = $this->resourceTypeRepository->get('menu_link_config', 'menu_link_config');
+      }
+      else {
+        $resource_type = $this->resourceTypeRepository->get('menu_link_content', $menu_link->link->getMenuName());
+        if ($resource_type === NULL) {
+          $resource_type = $this->resourceTypeRepository->get('menu_link_content', 'menu_link_content');
+        }
+      }
+
+      $url = $menu_link->link->getUrlObject()->toString(TRUE);
+      assert($url instanceof GeneratedUrl);
+      $cache->addCacheableDependency($url);
+
+      $links = new LinkCollection([]);
+
+      $resource_object_cacheability = new CacheableMetadata();
+      $resource_object_cacheability->addCacheableDependency($menu_link->access);
+      $resource_object_cacheability->addCacheableDependency($cache);
+
+      $fields = $this->buildMenuLinkSubtree($menu_link, $resource_object_cacheability);
+      $items[$id] = new ResourceObject($resource_object_cacheability, $resource_type, $id, NULL, $fields, $links);
+    }
+  }
+
+  /**
+   * Recursively generates the data structure for a menu link and its children.
+   *
+   * Each child link is nested under the `subTree` key of its parent link,
+   * creating a tree-like representation of the menu.
+   *
+   * @param array $menuLink
+   *   The menu link data to process.
+   * @param \Drupal\Core\Cache\CacheableMetadata $cache
+   *   The cacheable metadata object to merge with the menu link's cache.
+   * @param int $depth
+   *   The current depth in the menu tree.
+   *
+   * @return array
+   *   A structured array representing the menu link and its nested children.
+   */
+  public function buildMenuLinkSubtree($menu_link, CacheableMetadata $cache, int $depth = 0) {
+
+    if ($menu_link->access !== NULL && !$menu_link->access instanceof AccessResultInterface) {
+      throw new \DomainException('MenuLinkTreeElement::access must be either NULL or an AccessResultInterface object.');
+    }
+
+    if ($menu_link->access instanceof AccessResultInterface) {
+      $cache->merge(CacheableMetadata::createFromObject($menu_link->access));
+    }
+
+    // Only build data for accessible links.
+    if ($menu_link->access instanceof AccessResultInterface && !$menu_link->access->isAllowed()) {
+      return [];
+    }
+
+    $url = $menu_link->link->getUrlObject()->toString(TRUE);
+    assert($url instanceof GeneratedUrl);
+    $cache->addCacheableDependency($url);
+    $cache->addCacheableDependency($menu_link->access);
+
+    $fields = [
+      'description' => $menu_link->link->getDescription(),
+      'enabled' => $menu_link->link->isEnabled(),
+      'expanded' => $menu_link->link->isExpanded(),
+      'menu_name' => $menu_link->link->getMenuName(),
+      'meta' => $menu_link->link->getMetaData(),
+      'options' => $menu_link->link->getOptions(),
+      'parent' => $menu_link->link->getParent(),
+      'provider' => $menu_link->link->getProvider(),
+      'route' => [
+        'name' => $menu_link->link->getRouteName(),
+        'parameters' => $menu_link->link->getRouteParameters(),
+      ],
+      'title' => (string) $menu_link->link->getTitle(),
+      'url' => $url->getGeneratedUrl(),
+      'weight' => (int) $menu_link->link->getWeight(),
+      'depth' => $depth,
+    ];
+
+    if ($menu_link->subtree) {
+      $depth++;
+      foreach ($menu_link->subtree as $link) {
+        /** @var \Drupal\Core\Menu\MenuLinkTreeElement $link */
+        if ($link->access instanceof AccessResultInterface && !$link->access->isAllowed()) {
+          continue;
+        }
+        $provider = $link->link->getProvider();
+        $child_data = [
+          "type" => $provider . '--' . $provider,
+          "id" => $link->link->getPluginId(),
+          "attributes" => $this->buildMenuLinkSubtree($link, $cache, $depth),
+        ];
+        $fields['subTree'][] = $child_data;
+      }
+    }
+    return $fields;
+  }
+
+}