<?php

/**
 * @file
 * API for the Drupal menu system.
 */

use Drupal\Component\Utility\NestedArray;
use Drupal\Component\Utility\String;
use Drupal\Core\Cache\CacheBackendInterface;
use Drupal\Core\Language\Language;
use Drupal\Core\Routing\RequestHelper;
use Drupal\Core\Template\Attribute;
use Drupal\menu_link\Entity\MenuLink;
use Drupal\menu_link\MenuLinkStorageController;
use Symfony\Cmf\Component\Routing\RouteObjectInterface;
use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpKernel\Exception\NotFoundHttpException;
use Symfony\Component\Routing\Route;

/**
 * @defgroup menu Menu and routing system
 * @{
 * Define the navigation menus, and route page requests to code based on URLs.
 *
 * The Drupal routing system defines how Drupal responds to URLs passed to the
 * browser. The menu system, which depends on the routing system, is used for
 * navigation. The Menu module allows menus to be created in the user interface
 * as hierarchical lists of links.
 *
 * @section registering_paths Registering router paths
 * To register a path, you need to add lines similar to this in a
 * module.routing.yml file:
 * @code
 * block.admin_display:
 *   path: '/admin/structure/block'
 *   defaults:
 *     _content: '\Drupal\block\Controller\BlockListController::listing'
 *   requirements:
 *     _permission: 'administer blocks'
 * @endcode
 * @todo Add more information here, especially about controllers and what all
 *   the stuff in the routing.yml file means.
 *
 * @section Defining menu links
 * Once you have a route defined, you can use hook_menu() to define links
 * for your module's paths in the main Navigation menu or other menus. See
 * the hook_menu() documentation for more details.
 *
 * @todo The rest of this topic has not been reviewed or updated for Drupal 8.x
 *   and is not correct!
 * @todo It is quite likely that hook_menu() will be replaced with a different
 *   hook, configuration system, or plugin system before the 8.0 release.
 *
 * Drupal's menu system follows a simple hierarchy defined by paths.
 * Implementations of hook_menu() define menu items and assign them to
 * paths (which should be unique). The menu system aggregates these items
 * and determines the menu hierarchy from the paths. For example, if the
 * paths defined were a, a/b, e, a/b/c/d, f/g, and a/b/h, the menu system
 * would form the structure:
 * - a
 *   - a/b
 *     - a/b/c/d
 *     - a/b/h
 * - e
 * - f/g
 * Note that the number of elements in the path does not necessarily
 * determine the depth of the menu item in the tree.
 *
 * When responding to a page request, the menu system looks to see if the
 * path requested by the browser is registered as a menu item with a
 * callback. If not, the system searches up the menu tree for the most
 * complete match with a callback it can find. If the path a/b/i is
 * requested in the tree above, the callback for a/b would be used.
 *
 * The found callback function is called with any arguments specified
 * in the "page arguments" attribute of its menu item. The
 * attribute must be an array. After these arguments, any remaining
 * components of the path are appended as further arguments. In this
 * way, the callback for a/b above could respond to a request for
 * a/b/i differently than a request for a/b/j.
 *
 * For an illustration of this process, see page_example.module.
 *
 * Access to the callback functions is also protected by the menu system.
 * The "access callback" with an optional "access arguments" of each menu
 * item is called before the page callback proceeds. If this returns TRUE,
 * then access is granted; if FALSE, then access is denied. Default local task
 * menu items (see next paragraph) may omit this attribute to use the value
 * provided by the parent item.
 *
 * In the default Drupal interface, you will notice many links rendered as
 * tabs. These are known in the menu system as "local tasks", and they are
 * rendered as tabs by default, though other presentations are possible.
 * Local tasks function just as other menu items in most respects. It is
 * convention that the names of these tasks should be short verbs if
 * possible. In addition, a "default" local task should be provided for
 * each set. When visiting a local task's parent menu item, the default
 * local task will be rendered as if it is selected; this provides for a
 * normal tab user experience. This default task is special in that it
 * links not to its provided path, but to its parent item's path instead.
 * The default task's path is only used to place it appropriately in the
 * menu hierarchy.
 *
 * Everything described so far is stored in the menu_router table. The
 * menu_links table holds the visible menu links. By default these are
 * derived from the same hook_menu definitions, however you are free to
 * add more with menu_link_save().
 */

/**
 * @defgroup menu_flags Menu flags
 * @{
 * Flags for use in the "type" attribute of menu items.
 */

/**
 * Internal menu flag -- menu item is the root of the menu tree.
 */
const MENU_IS_ROOT = 0x0001;

/**
 * Internal menu flag -- menu item is visible in the menu tree.
 */
const MENU_VISIBLE_IN_TREE = 0x0002;

/**
 * Internal menu flag -- menu item is visible in the breadcrumb.
 */
const MENU_VISIBLE_IN_BREADCRUMB = 0x0004;

/**
 * Internal menu flag -- menu item links back to its parent.
 */
const MENU_LINKS_TO_PARENT = 0x0008;

/**
 * Internal menu flag -- menu item can be modified by administrator.
 */
const MENU_MODIFIED_BY_ADMIN = 0x0020;

/**
 * Internal menu flag -- menu item was created by administrator.
 */
const MENU_CREATED_BY_ADMIN = 0x0040;

/**
 * Internal menu flag -- menu item is a local task.
 */
const MENU_IS_LOCAL_TASK = 0x0080;

/**
 * @} End of "defgroup menu_flags".
 */

/**
 * @defgroup menu_item_types Menu item types
 * @{
 * Definitions for various menu item types.
 *
 * Menu item definitions provide one of these constants, which are shortcuts for
 * combinations of @link menu_flags Menu flags @endlink.
 */

/**
 * Menu type -- A "normal" menu item that's shown in menus.
 *
 * Normal menu items show up in the menu tree and can be moved/hidden by
 * the administrator. Use this for most menu items. It is the default value if
 * no menu item type is specified.
 */
define('MENU_NORMAL_ITEM', MENU_VISIBLE_IN_TREE | MENU_VISIBLE_IN_BREADCRUMB);

/**
 * Menu type -- A hidden, internal callback, typically used for API calls.
 *
 * Callbacks simply register a path so that the correct function is fired
 * when the URL is accessed. They do not appear in menus.
 */
const MENU_CALLBACK = 0x0000;

/**
 * Menu type -- A normal menu item, hidden until enabled by an administrator.
 *
 * Modules may "suggest" menu items that the administrator may enable. They act
 * just as callbacks do until enabled, at which time they act like normal items.
 * Note for the value: 0x0010 was a flag which is no longer used, but this way
 * the values of MENU_CALLBACK and MENU_SUGGESTED_ITEM are separate.
 */
define('MENU_SUGGESTED_ITEM', MENU_VISIBLE_IN_BREADCRUMB | 0x0010);

/**
 * Menu type -- A task specific to the parent item, usually rendered as a tab.
 *
 * Local tasks are menu items that describe actions to be performed on their
 * parent item. An example is the path "node/52/edit", which performs the
 * "edit" task on "node/52".
 */
define('MENU_LOCAL_TASK', MENU_IS_LOCAL_TASK | MENU_VISIBLE_IN_BREADCRUMB);

/**
 * Menu type -- The "default" local task, which is initially active.
 *
 * Every set of local tasks should provide one "default" task, that links to the
 * same path as its parent when clicked.
 */
define('MENU_DEFAULT_LOCAL_TASK', MENU_IS_LOCAL_TASK | MENU_LINKS_TO_PARENT | MENU_VISIBLE_IN_BREADCRUMB);

/**
 * Menu type -- A task specific to the parent, which is never rendered.
 *
 * Sibling local tasks are not rendered themselves, but affect the active
 * trail and need their sibling tasks rendered as tabs.
 */
define('MENU_SIBLING_LOCAL_TASK', MENU_IS_LOCAL_TASK | MENU_VISIBLE_IN_BREADCRUMB);

/**
 * @} End of "defgroup menu_item_types".
 */

/**
 * @defgroup menu_context_types Menu context types
 * @{
 * Flags for use in the "context" attribute of menu router items.
 */

/**
 * Internal menu flag: Invisible local task.
 *
 * This flag may be used for local tasks like "Delete", so custom modules and
 * themes can alter the default context and expose the task by altering menu.
 */
const MENU_CONTEXT_NONE = 0x0000;

/**
 * Internal menu flag: Local task should be displayed in page context.
 */
const MENU_CONTEXT_PAGE = 0x0001;

/**
 * @} End of "defgroup menu_context_types".
 */

/**
 * @defgroup menu_status_codes Menu status codes
 * @{
 * Status codes for menu callbacks.
 */

/**
 * Internal menu status code -- Menu item was not found.
 */
const MENU_NOT_FOUND = 404;

/**
 * Internal menu status code -- Menu item access is denied.
 */
const MENU_ACCESS_DENIED = 403;

/**
 * Internal menu status code -- Menu item inaccessible because site is offline.
 */
const MENU_SITE_OFFLINE = 4;

/**
 * Internal menu status code -- Everything is working fine.
 */
const MENU_SITE_ONLINE = 5;

/**
 * @} End of "defgroup menu_status_codes".
 */

/**
 * @defgroup menu_tree_parameters Menu tree parameters
 * @{
 * Parameters for a menu tree.
 */

 /**
 * The maximum number of path elements for a menu callback
 */
const MENU_MAX_PARTS = 9;


/**
 * The maximum depth of a menu links tree - matches the number of p columns.
 *
 * @todo Move this constant to MenuLinkStorageController along with all the tree
 * functionality.
 */
const MENU_MAX_DEPTH = 9;


/**
 * @} End of "defgroup menu_tree_parameters".
 */

/**
 * Reserved key to identify the most specific menu link for a given path.
 *
 * The value of this constant is a hash of the constant name. We use the hash
 * so that the reserved key is over 32 characters in length and will not
 * collide with allowed menu names:
 * @code
 * sha1('MENU_PREFERRED_LINK') = 1cf698d64d1aa4b83907cf6ed55db3a7f8e92c91
 * @endcode
 *
 * @see menu_link_get_preferred()
 */
const MENU_PREFERRED_LINK = '1cf698d64d1aa4b83907cf6ed55db3a7f8e92c91';

/**
 * Returns the ancestors (and relevant placeholders) for any given path.
 *
 * For example, the ancestors of node/12345/edit are:
 * - node/12345/edit
 * - node/12345/%
 * - node/%/edit
 * - node/%/%
 * - node/12345
 * - node/%
 * - node
 *
 * To generate these, we will use binary numbers. Each bit represents a
 * part of the path. If the bit is 1, then it represents the original
 * value while 0 means wildcard. If the path is node/12/edit/foo
 * then the 1011 bitstring represents node/%/edit/foo where % means that
 * any argument matches that part. We limit ourselves to using binary
 * numbers that correspond the patterns of wildcards of router items that
 * actually exists. This list of 'masks' is built in menu_router_rebuild().
 *
 * @param $parts
 *   An array of path parts, for the above example
 *   array('node', '12345', 'edit').
 *
 * @return
 *   An array which contains the ancestors and placeholders. Placeholders
 *   simply contain as many '%s' as the ancestors.
 */
function menu_get_ancestors($parts) {
  $number_parts = count($parts);
  $ancestors = array();
  $length =  $number_parts - 1;
  $end = (1 << $number_parts) - 1;
  $masks = \Drupal::state()->get('menu.masks');
  // If the optimized menu.masks array is not available use brute force to get
  // the correct $ancestors and $placeholders returned. Do not use this as the
  // default value of the menu.masks variable to avoid building such a big
  // array.
  if (!$masks) {
    $masks = range(511, 1);
  }
  // Only examine patterns that actually exist as router items (the masks).
  foreach ($masks as $i) {
    if ($i > $end) {
      // Only look at masks that are not longer than the path of interest.
      continue;
    }
    elseif ($i < (1 << $length)) {
      // We have exhausted the masks of a given length, so decrease the length.
      --$length;
    }
    $current = '';
    for ($j = $length; $j >= 0; $j--) {
      // Check the bit on the $j offset.
      if ($i & (1 << $j)) {
        // Bit one means the original value.
        $current .= $parts[$length - $j];
      }
      else {
        // Bit zero means means wildcard.
        $current .= '%';
      }
      // Unless we are at offset 0, add a slash.
      if ($j) {
        $current .= '/';
      }
    }
    $ancestors[] = $current;
  }
  return $ancestors;
}

/**
 * Unserializes menu data, using a map to replace path elements.
 *
 * The menu system stores various path-related information (such as the 'page
 * arguments' and 'access arguments' components of a menu item) in the database
 * using serialized arrays, where integer values in the arrays represent
 * arguments to be replaced by values from the path. This function first
 * unserializes such menu information arrays, and then does the path
 * replacement.
 *
 * The path replacement acts on each integer-valued element of the unserialized
 * menu data array ($data) using a map array ($map, which is typically an array
 * of path arguments) as a list of replacements. For instance, if there is an
 * element of $data whose value is the number 2, then it is replaced in $data
 * with $map[2]; non-integer values in $data are left alone.
 *
 * As an example, an unserialized $data array with elements ('node_load', 1)
 * represents instructions for calling the node_load() function. Specifically,
 * this instruction says to use the path component at index 1 as the input
 * parameter to node_load(). If the path is 'node/123', then $map will be the
 * array ('node', 123), and the returned array from this function will have
 * elements ('node_load', 123), since $map[1] is 123. This return value will
 * indicate specifically that node_load(123) is to be called to load the node
 * whose ID is 123 for this menu item.
 *
 * @param $data
 *   A serialized array of menu data, as read from the database.
 * @param $map
 *   A path argument array, used to replace integer values in $data; an integer
 *   value N in $data will be replaced by value $map[N]. Typically, the $map
 *   array is generated from a call to the arg() function.
 *
 * @return
 *   The unserialized $data array, with path arguments replaced.
 */
function menu_unserialize($data, $map) {
  if ($data = unserialize($data)) {
    foreach ($data as $k => $v) {
      if (is_int($v)) {
        $data[$k] = isset($map[$v]) ? $map[$v] : '';
      }
    }
    return $data;
  }
  else {
    return array();
  }
}


/**
 * Replaces the statically cached item for a given path.
 *
 * @param $path
 *   The path.
 * @param $router_item
 *   The router item. Usually a router entry from menu_get_item() is either
 *   modified or set to a different path. This allows the navigation block,
 *   the page title, the active trail, and the page help to be modified in one
 *   call.
 */
function menu_set_item($path, $router_item) {
  menu_get_item($path, $router_item);
}

/**
 * Gets a router item.
 *
 * @param $path
 *   The path; for example, 'node/5'. The function will find the corresponding
 *   node/% item and return that.
 * @param $router_item
 *   Internal use only.
 *
 * @return
 *   The router item or, if an error occurs in _menu_translate(), FALSE. A
 *   router item is an associative array corresponding to one row in the
 *   menu_router table. The value corresponding to the key 'map' holds the
 *   loaded objects. The value corresponding to the key 'access' is TRUE if the
 *   current user can access this page. The values corresponding to the keys
 *   'title', 'page_arguments', and 'access_arguments', will be filled in based
 *   on the database values and the objects loaded.
 */
function menu_get_item($path = NULL, $router_item = NULL) {
  $router_items = &drupal_static(__FUNCTION__);
  if (!isset($path)) {
    $path = current_path();
  }
  if (isset($router_item)) {
    $router_items[$path] = $router_item;
  }
  if (!isset($router_items[$path])) {
    // Rebuild if we know it's needed, or if the menu masks are missing which
    // occurs rarely, likely due to a race condition of multiple rebuilds.
    if (\Drupal::state()->get('menu_rebuild_needed') || !\Drupal::state()->get('menu.masks')) {
      menu_router_rebuild();
      \Drupal::service('router.builder')->rebuild();
    }
    $original_map = arg(NULL, $path);

    $parts = array_slice($original_map, 0, MENU_MAX_PARTS);
    $ancestors = menu_get_ancestors($parts);
    $router_item = db_query_range('SELECT * FROM {menu_router} WHERE path IN (:ancestors) ORDER BY fit DESC', 0, 1, array(':ancestors' => $ancestors))->fetchAssoc();

    if ($router_item) {
      // Allow modules to alter the router item before it is translated and
      // checked for access.
      drupal_alter('menu_get_item', $router_item, $path, $original_map);

      $map = _menu_translate($router_item, $original_map);
      $router_item['original_map'] = $original_map;
      if ($map === FALSE) {
        $router_items[$path] = FALSE;
        return FALSE;
      }
      if ($router_item['access']) {
        $router_item['map'] = $map;
        $router_item['page_arguments'] = array_merge(menu_unserialize($router_item['page_arguments'], $map), array_slice($map, $router_item['number_parts']));
      }
    }
    $router_items[$path] = $router_item;
  }
  return $router_items[$path];
}

/**
 * Loads objects into the map as defined in the $item['load_functions'].
 *
 * @param $item
 *   A menu router or menu link item
 * @param $map
 *   An array of path arguments; for example, array('node', '5').
 *
 * @return
 *   Returns TRUE for success, FALSE if an object cannot be loaded.
 *   Names of object loading functions are placed in $item['load_functions'].
 *   Loaded objects are placed in $map[]; keys are the same as keys in the
 *   $item['load_functions'] array.
 *   $item['access'] is set to FALSE if an object cannot be loaded.
 */
function _menu_load_objects(&$item, &$map) {
  if ($load_functions = $item['load_functions']) {
    // If someone calls this function twice, then unserialize will fail.
    if (!is_array($load_functions)) {
      $load_functions = unserialize($load_functions);
    }
    $path_map = $map;
    foreach ($load_functions as $index => $function) {
      if ($function) {
        $value = isset($path_map[$index]) ? $path_map[$index] : '';
        if (is_array($function)) {
          // Set up arguments for the load function. These were pulled from
          // 'load arguments' in the hook_menu() entry, but they need
          // some processing. In this case the $function is the key to the
          // load_function array, and the value is the list of arguments.
          list($function, $args) = each($function);
          $load_functions[$index] = $function;

          // Some arguments are placeholders for dynamic items to process.
          foreach ($args as $i => $arg) {
            if ($arg === '%index') {
              // Pass on argument index to the load function, so multiple
              // occurrences of the same placeholder can be identified.
              $args[$i] = $index;
            }
            if ($arg === '%map') {
              // Pass on menu map by reference. The accepting function must
              // also declare this as a reference if it wants to modify
              // the map.
              $args[$i] = &$map;
            }
            if (is_int($arg)) {
              $args[$i] = isset($path_map[$arg]) ? $path_map[$arg] : '';
            }
          }
          array_unshift($args, $value);
          $return = call_user_func_array($function, $args);
        }
        else {
          $return = $function($value);
        }
        // If callback returned an error or there is no callback, trigger 404.
        if (empty($return)) {
          $item['access'] = FALSE;
          $map = FALSE;
          return FALSE;
        }
        $map[$index] = $return;
      }
    }
    $item['load_functions'] = $load_functions;
  }
  return TRUE;
}

/**
 * Checks access to a menu item using the access callback.
 *
 * @param $item
 *   A menu router or menu link item
 * @param $map
 *   An array of path arguments; for example, array('node', '5').
 *
 * @return
 *   $item['access'] becomes TRUE if the item is accessible, FALSE otherwise.
 */
function _menu_check_access(&$item, $map) {
  // Determine access callback, which will decide whether or not the current
  // user has access to this path.
  $callback = empty($item['access_callback']) ? 0 : trim($item['access_callback']);
  // Check for a TRUE or FALSE value.
  if (is_numeric($callback)) {
    $item['access'] = (bool) $callback;
  }
  else {
    $arguments = menu_unserialize($item['access_arguments'], $map);
    // As call_user_func_array is quite slow and user_access is a very common
    // callback, it is worth making a special case for it.
    if ($callback == 'user_access') {
      $item['access'] = (count($arguments) == 1) ? user_access($arguments[0]) : user_access($arguments[0], $arguments[1]);
    }
    else {
      $item['access'] = call_user_func_array($callback, $arguments);
    }
  }
}

/**
 * Localizes the router item title using t() or another callback.
 *
 * Translate the title and description to allow storage of English title
 * strings in the database, yet display of them in the language required
 * by the current user.
 *
 * @param $item
 *   A menu router item or a menu link item.
 * @param $map
 *   The path as an array with objects already replaced. E.g., for path
 *   node/123 $map would be array('node', $node) where $node is the node
 *   object for node 123.
 * @param $link_translate
 *   TRUE if we are translating a menu link item; FALSE if we are
 *   translating a menu router item.
 *
 * @return
 *   No return value.
 *   $item['title'] is localized according to $item['title_callback'].
 *   If an item's callback is check_plain(), $item['options']['html'] becomes
 *   TRUE.
 *   $item['description'] is computed using $item['description_callback'] if
 *   specified; otherwise it is translated using t().
 *   When doing link translation and the $item['options']['attributes']['title']
 *   (link title attribute) matches the description, it is translated as well.
 */
function _menu_item_localize(&$item, $map, $link_translate = FALSE) {
  $title_callback = $item['title_callback'];
  $item['localized_options'] = $item['options'];
  // All 'class' attributes are assumed to be an array during rendering, but
  // links stored in the database may use an old string value.
  // @todo In order to remove this code we need to implement a database update
  //   including unserializing all existing link options and running this code
  //   on them, as well as adding validation to menu_link_save().
  if (isset($item['options']['attributes']['class']) && is_string($item['options']['attributes']['class'])) {
    $item['localized_options']['attributes']['class'] = explode(' ', $item['options']['attributes']['class']);
  }
  // If we are translating the title of a menu link, and its title is the same
  // as the corresponding router item, then we can use the title information
  // from the router. If it's customized, then we need to use the link title
  // itself; can't localize.
  // If we are translating a router item (tabs, page, breadcrumb), then we
  // can always use the information from the router item.
  if (!$link_translate || ($item['title'] == $item['link_title'])) {
    // t() is a special case. Since it is used very close to all the time,
    // we handle it directly instead of using indirect, slower methods.
    if ($title_callback == 't') {
      if (empty($item['title_arguments'])) {
        $item['title'] = t($item['title']);
      }
      else {
        $item['title'] = t($item['title'], menu_unserialize($item['title_arguments'], $map));
      }
    }
    elseif ($title_callback) {
      if (empty($item['title_arguments'])) {
        $item['title'] = $title_callback($item['title']);
      }
      else {
        $item['title'] = call_user_func_array($title_callback, menu_unserialize($item['title_arguments'], $map));
      }
      // Avoid calling check_plain again on l() function.
      if ($title_callback == 'check_plain') {
        $item['localized_options']['html'] = TRUE;
      }
    }
  }
  elseif ($link_translate) {
    $item['title'] = $item['link_title'];
  }

  // Translate description, see the motivation above.
  if (!empty($item['description'])) {
    $original_description = $item['description'];
  }
  if (!empty($item['description_arguments']) || !empty($item['description'])) {
    $description_callback = $item['description_callback'];
    // If the description callback is t(), call it directly.
    if ($description_callback == 't') {
      if (empty($item['description_arguments'])) {
        $item['description'] = t($item['description']);
      }
      else {
        $item['description'] = t($item['description'], menu_unserialize($item['description_arguments'], $map));
      }
    }
    elseif ($description_callback) {
      // If there are no arguments, call the description callback directly.
      if (empty($item['description_arguments'])) {
        $item['description'] = $description_callback($item['description']);
      }
      // Otherwise, use call_user_func_array() to pass the arguments.
      else {
        $item['description'] = call_user_func_array($description_callback, menu_unserialize($item['description_arguments'], $map));
      }
    }
  }
  // If the title and description are the same, use the translated description
  // as a localized title.
  if ($link_translate && isset($original_description) && isset($item['options']['attributes']['title']) && $item['options']['attributes']['title'] == $original_description) {
    $item['localized_options']['attributes']['title'] = $item['description'];
  }
}

/**
 * Handles dynamic path translation and menu access control.
 *
 * When a user arrives on a page such as node/5, this function determines
 * what "5" corresponds to, by inspecting the page's menu path definition,
 * node/%node. This will call node_load(5) to load the corresponding node
 * object.
 *
 * It also works in reverse, to allow the display of tabs and menu items which
 * contain these dynamic arguments, translating node/%node to node/5.
 *
 * Translation of menu item titles and descriptions are done here to
 * allow for storage of English strings in the database, and translation
 * to the language required to generate the current page.
 *
 * @param $router_item
 *   A menu router item
 * @param $map
 *   An array of path arguments; for example, array('node', '5').
 * @param $to_arg
 *   Execute $item['to_arg_functions'] or not. Use only if you want to render a
 *   path from the menu table, for example tabs.
 *
 * @return
 *   Returns the map with objects loaded as defined in the
 *   $item['load_functions']. $item['access'] becomes TRUE if the item is
 *   accessible, FALSE otherwise. $item['href'] is set according to the map.
 *   If an error occurs during calling the load_functions (like trying to load
 *   a non-existent node) then this function returns FALSE.
 */
function _menu_translate(&$router_item, $map, $to_arg = FALSE) {
  if ($to_arg && !empty($router_item['to_arg_functions'])) {
    // Fill in missing path elements, such as the current uid.
    _menu_link_map_translate($map, $router_item['to_arg_functions']);
  }
  // The $path_map saves the pieces of the path as strings, while elements in
  // $map may be replaced with loaded objects.
  $path_map = $map;
  if (!empty($router_item['load_functions']) && !_menu_load_objects($router_item, $map)) {
    // An error occurred loading an object.
    $router_item['access'] = FALSE;
    return FALSE;
  }

  // Generate the link path for the page request or local tasks.
  $link_map = explode('/', $router_item['path']);
  if (isset($router_item['tab_root'])) {
    $tab_root_map = explode('/', $router_item['tab_root']);
  }
  if (isset($router_item['tab_parent'])) {
    $tab_parent_map = explode('/', $router_item['tab_parent']);
  }
  for ($i = 0; $i < $router_item['number_parts']; $i++) {
    if ($link_map[$i] == '%') {
      $link_map[$i] = $path_map[$i];
    }
    if (isset($tab_root_map[$i]) && $tab_root_map[$i] == '%') {
      $tab_root_map[$i] = $path_map[$i];
    }
    if (isset($tab_parent_map[$i]) && $tab_parent_map[$i] == '%') {
      $tab_parent_map[$i] = $path_map[$i];
    }
  }
  $router_item['href'] = implode('/', $link_map);
  $router_item['tab_root_href'] = implode('/', $tab_root_map);
  $router_item['tab_parent_href'] = implode('/', $tab_parent_map);
  $router_item['options'] = array();
  if (!empty($router_item['route_name'])) {
    // Route-provided menu items do not have menu loaders, so replace the map
    // with the link map.
    $map = $link_map;

    $route_provider = \Drupal::getContainer()->get('router.route_provider');
    $route = $route_provider->getRouteByName($router_item['route_name']);
    $router_item['access'] = menu_item_route_access($route, $router_item['href'], $map);
  }
  else {
    // @todo: Remove once all routes are converted.
    _menu_check_access($router_item, $map);
  }

  // For performance, don't localize an item the user can't access.
  if ($router_item['access']) {
    _menu_item_localize($router_item, $map);
  }

  return $map;
}

/**
 * Translates the path elements in the map using any to_arg helper function.
 *
 * @param $map
 *   An array of path arguments; for example, array('node', '5').
 * @param $to_arg_functions
 *   An array of helper functions; for example, array(2 => 'menu_tail_to_arg').
 *
 * @see hook_menu()
 */
function _menu_link_map_translate(&$map, $to_arg_functions) {
  $to_arg_functions = unserialize($to_arg_functions);
  foreach ($to_arg_functions as $index => $function) {
    // Translate place-holders into real values.
    $arg = $function(!empty($map[$index]) ? $map[$index] : '', $map, $index);
    if (!empty($map[$index]) || isset($arg)) {
      $map[$index] = $arg;
    }
    else {
      unset($map[$index]);
    }
  }
}

/**
 * Returns a string containing the path relative to the current index.
 */
function menu_tail_to_arg($arg, $map, $index) {
  return implode('/', array_slice($map, $index));
}

/**
 * Loads the path as one string relative to the current index.
 *
 * To use this load function, you must specify the load arguments
 * in the router item as:
 * @code
 * $item['load arguments'] = array('%map', '%index');
 * @endcode
 *
 * @see search_menu().
 */
function menu_tail_load($arg, &$map, $index) {
  $arg = implode('/', array_slice($map, $index));
  $map = array_slice($map, 0, $index);
  return $arg;
}

/**
 * Provides menu link access control, translation, and argument handling.
 *
 * This function is similar to _menu_translate(), but it also does
 * link-specific preparation (such as always calling to_arg() functions).
 *
 * @param $item
 *   A menu link.
 * @param $translate
 *   (optional) Whether to try to translate a link containing dynamic path
 *   argument placeholders (%) based on the menu router item of the current
 *   path. Defaults to FALSE. Internally used for breadcrumbs.
 *
 * @return
 *   Returns the map of path arguments with objects loaded as defined in the
 *   $item['load_functions'].
 *   $item['access'] becomes TRUE if the item is accessible, FALSE otherwise.
 *   $item['href'] is generated from link_path, possibly by to_arg functions.
 *   $item['title'] is generated from link_title, and may be localized.
 *   $item['options'] is unserialized; it is also changed within the call here
 *   to $item['localized_options'] by _menu_item_localize().
 */
function _menu_link_translate(&$item, $translate = FALSE) {
  if (!is_array($item['options'])) {
    $item['options'] = unserialize($item['options']);
  }
  if ($item['external']) {
    $item['access'] = 1;
    $map = array();
    $item['href'] = $item['link_path'];
    $item['title'] = $item['link_title'];
    $item['localized_options'] = $item['options'];
  }
  else {
    // Complete the path of the menu link with elements from the current path,
    // if it contains dynamic placeholders (%).
    $map = explode('/', $item['link_path']);
    if (strpos($item['link_path'], '%') !== FALSE) {
      // Invoke registered to_arg callbacks.
      if (!empty($item['to_arg_functions'])) {
        _menu_link_map_translate($map, $item['to_arg_functions']);
      }
      // Or try to derive the path argument map from the current router item,
      // if this $item's path is within the router item's path. This means
      // that if we are on the current path 'foo/%/bar/%/baz', then
      // menu_get_item() will have translated the menu router item for the
      // current path, and we can take over the argument map for a link like
      // 'foo/%/bar'. This inheritance is only valid for breadcrumb links.
      // @see _menu_tree_check_access()
      elseif ($translate && ($current_router_item = menu_get_item())) {
        // If $translate is TRUE, then this link is in the active trail.
        // Only translate paths within the current path.
        if (strpos($current_router_item['path'], $item['link_path']) === 0) {
          $count = count($map);
          $map = array_slice($current_router_item['original_map'], 0, $count);
          $item['original_map'] = $map;
          if (isset($current_router_item['map'])) {
            $item['map'] = array_slice($current_router_item['map'], 0, $count);
          }
          // Reset access to check it (for the first time).
          unset($item['access']);
        }
      }
    }
    $item['href'] = implode('/', $map);

    // Skip links containing untranslated arguments.
    if (strpos($item['href'], '%') !== FALSE) {
      $item['access'] = FALSE;
      return FALSE;
    }
    // menu_tree_check_access() may set this ahead of time for links to nodes.
    if (!isset($item['access'])) {
      if ($route = $item->getRoute()) {
        $item['access'] = menu_item_route_access($route, $item['href'], $map);
      }
      elseif (!empty($item['load_functions']) && !_menu_load_objects($item, $map)) {
        // An error occurred loading an object.
        $item['access'] = FALSE;
        return FALSE;
      }
      // Apply the access check defined in hook_menu() if there is not route
      // defined.
      else {
        _menu_check_access($item, $map);
      }
    }
    // For performance, don't localize a link the user can't access.
    if ($item['access']) {
      _menu_item_localize($item, $map, TRUE);
    }
  }

  // Allow other customizations - e.g. adding a page-specific query string to the
  // options array. For performance reasons we only invoke this hook if the link
  // has the 'alter' flag set in the options array.
  if (!empty($item['options']['alter'])) {
    drupal_alter('translated_menu_link', $item, $map);
  }

  return $map;
}

/**
 * Checks access to a menu item by mocking a request for a path.
 *
 * @param \Symfony\Component\Routing\Route $route
 *   Router for the given menu item.
 * @param string $href
 *   Menu path as returned by $item['href'] of menu_get_item().
 * @param array $map
 *   An array of path arguments; for example, array('node', '5').
 *
 * @return bool
 *   TRUE if the user has access or FALSE if the user should be presented
 *   with access denied.
 *
 * @throws \Symfony\Component\Routing\Exception\ResourceNotFoundException
 *   If the system path in $href does not match the $route.
 */
function menu_item_route_access(Route $route, $href, &$map) {
  $request = RequestHelper::duplicate(\Drupal::request(), '/' . $href);
  $request->attributes->set('_system_path', $href);
  // Attempt to match this path to provide a fully built request to the
  // access checker.
  try {
    $request->attributes->add(\Drupal::service('router')->matchRequest($request));
  }
  catch (NotFoundHttpException $e) {
    return FALSE;
  }

  // Populate the map with any matching values from the request.
  $path_bits = explode('/', trim($route->getPath(), '/'));
  foreach ($map as $index => $map_item) {
    $matches = array();
    // Search for placeholders wrapped by curly braces. For example, a path
    // 'foo/{bar}/baz' would return 'bar'.
    if (isset($path_bits[$index]) && preg_match('/{(?<placeholder>.*)}/', $path_bits[$index], $matches)) {
      // If that placeholder is present on the request attributes, replace the
      // placeholder in the map with the value.
      if ($request->attributes->has($matches['placeholder'])) {
        $map[$index] = $request->attributes->get($matches['placeholder']);
      }
    }
  }

  return \Drupal::service('access_manager')->check($route, $request, \Drupal::currentUser());
}

/**
 * Gets a loaded object from a router item.
 *
 * menu_get_object() provides access to objects loaded by the current router
 * item. For example, on the page node/%node, the router loads the %node object,
 * and calling menu_get_object() will return that. Normally, it is necessary to
 * specify the type of object referenced, however node is the default.
 * The following example tests to see whether the node being displayed is of the
 * "story" content type:
 * @code
 * $node = menu_get_object();
 * $story = $node->getType() == 'story';
 * @endcode
 *
 * @param $type
 *   Type of the object. These appear in hook_menu definitions as %type. Core
 *   provides aggregator_feed, aggregator_category, contact, filter_format,
 *   forum_term, menu, menu_link, node, taxonomy_vocabulary, user. See the
 *   relevant {$type}_load function for more on each. Defaults to node.
 * @param $position
 *   The position of the object in the path, where the first path segment is 0.
 *   For node/%node, the position of %node is 1, but for comment/reply/%node,
 *   it's 2. Defaults to 1.
 * @param $path
 *   See menu_get_item() for more on this. Defaults to the current path.
 *
 * @todo Remove this function in https://drupal.org/node/2091399.
 */
function menu_get_object($type = 'node', $position = 1, $path = NULL) {
  $router_item = menu_get_item($path);
  if (empty($router_item['map'][$position])) {
    return;
  }

  if (isset($router_item['load_functions'][$position]) && $router_item['load_functions'][$position] == $type . '_load') {
    return $router_item['map'][$position];
  }

  // If the path is route-based, use the route path instead of the menu item.
  // The most common use of this function is for the node page, which has a
  // route path of '/node/{node}'. By splitting that path into parts, we check
  // for the $type wrapped in curly braces at the correct $position, returning
  // the value found there.
  $request = \Drupal::request();
  if ($request->attributes->has(RouteObjectInterface::ROUTE_OBJECT)) {
    $path = $request->attributes->get(RouteObjectInterface::ROUTE_OBJECT)->getPath();
    $parts = explode('/', ltrim($path, '/'));
    if (isset($parts[$position]) && $parts[$position] == '{' . $type . '}') {
      return $router_item['map'][$position];
    }
  }
}

/**
 * Renders a menu tree based on the current path.
 *
 * The tree is expanded based on the current path and dynamic paths are also
 * changed according to the defined to_arg functions (for example the 'My
 * account' link is changed from user/% to a link with the current user's uid).
 *
 * @param $menu_name
 *   The name of the menu.
 *
 * @return
 *   A structured array representing the specified menu on the current page, to
 *   be rendered by drupal_render().
 */
function menu_tree($menu_name) {
  $menu_output = &drupal_static(__FUNCTION__, array());

  if (!isset($menu_output[$menu_name])) {
    $tree = menu_tree_page_data($menu_name);
    $menu_output[$menu_name] = menu_tree_output($tree);
  }
  return $menu_output[$menu_name];
}

/**
 * Returns a rendered menu tree.
 *
 * The menu item's LI element is given one of the following classes:
 * - expanded: The menu item is showing its submenu.
 * - collapsed: The menu item has a submenu which is not shown.
 * - leaf: The menu item has no submenu.
 *
 * @param $tree
 *   A data structure representing the tree as returned from menu_tree_data.
 *
 * @return
 *   A structured array to be rendered by drupal_render().
 */
function menu_tree_output($tree) {
  $build = array();
  $items = array();

  // Pull out just the menu links we are going to render so that we
  // get an accurate count for the first/last classes.
  foreach ($tree as $data) {
    if ($data['link']['access'] && !$data['link']['hidden']) {
      $items[] = $data;
    }
  }

  $router_item = menu_get_item();
  $num_items = count($items);
  foreach ($items as $i => $data) {
    $class = array();
    if ($i == 0) {
      $class[] = 'first';
    }
    if ($i == $num_items - 1) {
      $class[] = 'last';
    }
    // Set a class for the <li>-tag. Since $data['below'] may contain local
    // tasks, only set 'expanded' class if the link also has children within
    // the current menu.
    if ($data['link']['has_children'] && $data['below']) {
      $class[] = 'expanded';
    }
    elseif ($data['link']['has_children']) {
      $class[] = 'collapsed';
    }
    else {
      $class[] = 'leaf';
    }
    // Set a class if the link is in the active trail.
    if ($data['link']['in_active_trail']) {
      $class[] = 'active-trail';
      $data['link']['localized_options']['attributes']['class'][] = 'active-trail';
    }
    // Normally, l() compares the href of every link with the current path and
    // sets the active class accordingly. But local tasks do not appear in menu
    // trees, so if the current path is a local task, and this link is its
    // tab root, then we have to set the class manually.
    if ($data['link']['href'] == $router_item['tab_root_href'] && $data['link']['href'] != current_path()) {
      $data['link']['localized_options']['attributes']['class'][] = 'active';
    }

    // Allow menu-specific theme overrides.
    $element['#theme'] = 'menu_link__' . strtr($data['link']['menu_name'], '-', '_');
    $element['#attributes']['class'] = $class;
    $element['#title'] = $data['link']['title'];
    $element['#href'] = $data['link']['href'];
    $element['#localized_options'] = !empty($data['link']['localized_options']) ? $data['link']['localized_options'] : array();
    $element['#below'] = $data['below'] ? menu_tree_output($data['below']) : $data['below'];
    $element['#original_link'] = $data['link'];
    // Index using the link's unique mlid.
    $build[$data['link']['mlid']] = $element;
  }
  if ($build) {
    // Make sure drupal_render() does not re-order the links.
    $build['#sorted'] = TRUE;
    // Add the theme wrapper for outer markup.
    // Allow menu-specific theme overrides.
    $build['#theme_wrappers'][] = 'menu_tree__' . strtr($data['link']['menu_name'], '-', '_');
  }

  return $build;
}

/**
 * Gets the data structure representing a named menu tree.
 *
 * Since this can be the full tree including hidden items, the data returned
 * may be used for generating an an admin interface or a select.
 *
 * @param $menu_name
 *   The named menu links to return
 * @param $link
 *   A fully loaded menu link, or NULL. If a link is supplied, only the
 *   path to root will be included in the returned tree - as if this link
 *   represented the current page in a visible menu.
 * @param $max_depth
 *   Optional maximum depth of links to retrieve. Typically useful if only one
 *   or two levels of a sub tree are needed in conjunction with a non-NULL
 *   $link, in which case $max_depth should be greater than $link['depth'].
 *
 * @return
 *   An tree of menu links in an array, in the order they should be rendered.
 */
function menu_tree_all_data($menu_name, $link = NULL, $max_depth = NULL) {
  $tree = &drupal_static(__FUNCTION__, array());
  $language_interface = language(Language::TYPE_INTERFACE);

  // Use $mlid as a flag for whether the data being loaded is for the whole tree.
  $mlid = isset($link['mlid']) ? $link['mlid'] : 0;
  // Generate a cache ID (cid) specific for this $menu_name, $link, $language, and depth.
  $cid = 'links:' . $menu_name . ':all:' . $mlid . ':' . $language_interface->id . ':' . (int) $max_depth;

  if (!isset($tree[$cid])) {
    // If the static variable doesn't have the data, check {cache_menu}.
    $cache = cache('menu')->get($cid);
    if ($cache && isset($cache->data)) {
      // If the cache entry exists, it contains the parameters for
      // menu_build_tree().
      $tree_parameters = $cache->data;
    }
    // If the tree data was not in the cache, build $tree_parameters.
    if (!isset($tree_parameters)) {
      $tree_parameters = array(
        'min_depth' => 1,
        'max_depth' => $max_depth,
      );
      if ($mlid) {
        // The tree is for a single item, so we need to match the values in its
        // p columns and 0 (the top level) with the plid values of other links.
        $parents = array(0);
        for ($i = 1; $i < MENU_MAX_DEPTH; $i++) {
          if (!empty($link["p$i"])) {
            $parents[] = $link["p$i"];
          }
        }
        $tree_parameters['expanded'] = $parents;
        $tree_parameters['active_trail'] = $parents;
        $tree_parameters['active_trail'][] = $mlid;
      }

      // Cache the tree building parameters using the page-specific cid.
      cache('menu')->set($cid, $tree_parameters, CacheBackendInterface::CACHE_PERMANENT, array('menu' => $menu_name));
    }

    // Build the tree using the parameters; the resulting tree will be cached
    // by _menu_build_tree()).
    $tree[$cid] = menu_build_tree($menu_name, $tree_parameters);
  }

  return $tree[$cid];
}

/**
 * Sets the path for determining the active trail of the specified menu tree.
 *
 * This path will also affect the breadcrumbs under some circumstances.
 * Breadcrumbs are built using the preferred link returned by
 * menu_link_get_preferred(). If the preferred link is inside one of the menus
 * specified in calls to menu_tree_set_path(), the preferred link will be
 * overridden by the corresponding path returned by menu_tree_get_path().
 *
 * Setting this path does not affect the main content; for that use
 * menu_set_active_item() instead.
 *
 * @param $menu_name
 *   The name of the affected menu tree.
 * @param $path
 *   The path to use when finding the active trail.
 */
function menu_tree_set_path($menu_name, $path = NULL) {
  $paths = &drupal_static(__FUNCTION__);
  if (isset($path)) {
    $paths[$menu_name] = $path;
  }
  return isset($paths[$menu_name]) ? $paths[$menu_name] : NULL;
}

/**
 * Gets the path for determining the active trail of the specified menu tree.
 *
 * @param $menu_name
 *   The menu name of the requested tree.
 *
 * @return
 *   A string containing the path. If no path has been specified with
 *   menu_tree_set_path(), NULL is returned.
 */
function menu_tree_get_path($menu_name) {
  return menu_tree_set_path($menu_name);
}

/**
 * Gets the data structure for a named menu tree, based on the current page.
 *
 * The tree order is maintained by storing each parent in an individual
 * field, see http://drupal.org/node/141866 for more.
 *
 * @param $menu_name
 *   The named menu links to return.
 * @param $max_depth
 *   (optional) The maximum depth of links to retrieve.
 * @param $only_active_trail
 *   (optional) Whether to only return the links in the active trail (TRUE)
 *   instead of all links on every level of the menu link tree (FALSE). Defaults
 *   to FALSE.
 *
 * @return
 *   An array of menu links, in the order they should be rendered. The array
 *   is a list of associative arrays -- these have two keys, link and below.
 *   link is a menu item, ready for theming as a link. Below represents the
 *   submenu below the link if there is one, and it is a subtree that has the
 *   same structure described for the top-level array.
 */
function menu_tree_page_data($menu_name, $max_depth = NULL, $only_active_trail = FALSE) {
  $tree = &drupal_static(__FUNCTION__, array());

  $language_interface = language(Language::TYPE_INTERFACE);

  // Check if the active trail has been overridden for this menu tree.
  $active_path = menu_tree_get_path($menu_name);
  // Load the router item corresponding to the current page.
  $request = \Drupal::request();
  $system_path = NULL;
  if ($route_name = $request->attributes->get(RouteObjectInterface::ROUTE_NAME)) {
    // @todo https://drupal.org/node/2068471 is adding support so we can tell
    // if this is called on a 404/403 page.
    $system_path = $request->attributes->get('_system_path');
    $page_not_403 = 1;
  }
  // @todo Remove once the old router system is removed.
  elseif ($request->attributes->has('_legacy')) {
    // Page is a 404 if no item is loaded.
    if ($item = menu_get_item($active_path)) {
      $system_path = $item['href'];
      // Variable to indicate that we are not serving an access denied response
      // for this page. Used to limit the number of links rendered.
      $page_not_403 = (int) $item['access'];
    }
  }
  if (isset($system_path)) {
    if (isset($max_depth)) {
      $max_depth = min($max_depth, MENU_MAX_DEPTH);
    }
    // Generate a cache ID (cid) specific for this page.
    $cid = 'links:' . $menu_name . ':page:' . $system_path . ':' . $language_interface->id . ':' . $page_not_403 . ':' . (int) $max_depth;
    // If we are asked for the active trail only, and $menu_name has not been
    // built and cached for this page yet, then this likely means that it
    // won't be built anymore, as this function is invoked from
    // template_preprocess_page(). So in order to not build a giant menu tree
    // that needs to be checked for access on all levels, we simply check
    // whether we have the menu already in cache, or otherwise, build a minimum
    // tree containing the active trail only.
    // @see menu_set_active_trail()
    if (!isset($tree[$cid]) && $only_active_trail) {
      $cid .= ':trail';
    }

    if (!isset($tree[$cid])) {
      // If the static variable doesn't have the data, check {cache_menu}.
      $cache = cache('menu')->get($cid);
      if ($cache && isset($cache->data)) {
        // If the cache entry exists, it contains the parameters for
        // menu_build_tree().
        $tree_parameters = $cache->data;
      }
      // If the tree data was not in the cache, build $tree_parameters.
      if (!isset($tree_parameters)) {
        $tree_parameters = array(
          'min_depth' => 1,
          'max_depth' => $max_depth,
        );
        // Parent mlids; used both as key and value to ensure uniqueness.
        // We always want all the top-level links with plid == 0.
        $active_trail = array(0 => 0);

        // If this page is accessible to the current user, build the tree
        // parameters accordingly.
        if ($page_not_403) {
          // Find a menu link corresponding to the current path. If $active_path
          // is NULL, let menu_link_get_preferred() determine the path.
          if ($active_link = menu_link_get_preferred($active_path, $menu_name)) {
            // The active link may only be taken into account to build the
            // active trail, if it resides in the requested menu. Otherwise,
            // we'd needlessly re-run _menu_build_tree() queries for every menu
            // on every page.
            if ($active_link['menu_name'] == $menu_name) {
              // Use all the coordinates, except the last one because there
              // can be no child beyond the last column.
              for ($i = 1; $i < MENU_MAX_DEPTH; $i++) {
                if ($active_link['p' . $i]) {
                  $active_trail[$active_link['p' . $i]] = $active_link['p' . $i];
                }
              }
              // If we are asked to build links for the active trail only, skip
              // the entire 'expanded' handling.
              if ($only_active_trail) {
                $tree_parameters['only_active_trail'] = TRUE;
              }
            }
          }
          $parents = $active_trail;

          $expanded = \Drupal::state()->get('menu_expanded');
          // Check whether the current menu has any links set to be expanded.
          if (!$only_active_trail && $expanded && in_array($menu_name, $expanded)) {
            // Collect all the links set to be expanded, and then add all of
            // their children to the list as well.
            do {
              $query = \Drupal::entityQuery('menu_link')
                ->condition('menu_name', $menu_name)
                ->condition('expanded', 1)
                ->condition('has_children', 1)
                ->condition('plid', $parents, 'IN')
                ->condition('mlid', $parents, 'NOT IN');
              $result = $query->execute();
              $parents += $result;
            } while (!empty($result));
          }
          $tree_parameters['expanded'] = $parents;
          $tree_parameters['active_trail'] = $active_trail;
        }
        // If access is denied, we only show top-level links in menus.
        else {
          $tree_parameters['expanded'] = $active_trail;
          $tree_parameters['active_trail'] = $active_trail;
        }
        // Cache the tree building parameters using the page-specific cid.
        cache('menu')->set($cid, $tree_parameters, CacheBackendInterface::CACHE_PERMANENT, array('menu' => $menu_name));
      }

      // Build the tree using the parameters; the resulting tree will be cached
      // by _menu_build_tree().
      $tree[$cid] = menu_build_tree($menu_name, $tree_parameters);
    }
    return $tree[$cid];
  }

  return array();
}

/**
 * Builds a menu tree, translates links, and checks access.
 *
 * @param $menu_name
 *   The name of the menu.
 * @param $parameters
 *   (optional) An associative array of build parameters. Possible keys:
 *   - expanded: An array of parent link ids to return only menu links that are
 *     children of one of the plids in this list. If empty, the whole menu tree
 *     is built, unless 'only_active_trail' is TRUE.
 *   - active_trail: An array of mlids, representing the coordinates of the
 *     currently active menu link.
 *   - only_active_trail: Whether to only return links that are in the active
 *     trail. This option is ignored, if 'expanded' is non-empty.
 *   - min_depth: The minimum depth of menu links in the resulting tree.
 *     Defaults to 1, which is the default to build a whole tree for a menu
 *     (excluding menu container itself).
 *   - max_depth: The maximum depth of menu links in the resulting tree.
 *   - conditions: An associative array of custom database select query
 *     condition key/value pairs; see _menu_build_tree() for the actual query.
 *
 * @return
 *   A fully built menu tree.
 */
function menu_build_tree($menu_name, array $parameters = array()) {
  // Build the menu tree.
  $data = _menu_build_tree($menu_name, $parameters);
  // Check access for the current user to each item in the tree.
  menu_tree_check_access($data['tree'], $data['node_links']);
  return $data['tree'];
}

/**
 * Builds a menu tree.
 *
 * This function may be used build the data for a menu tree only, for example
 * to further massage the data manually before further processing happens.
 * menu_tree_check_access() needs to be invoked afterwards.
 *
 * @see menu_build_tree()
 */
function _menu_build_tree($menu_name, array $parameters = array()) {
  // Static cache of already built menu trees.
  $trees = &drupal_static(__FUNCTION__, array());
  $language_interface = language(Language::TYPE_INTERFACE);

  // Build the cache id; sort parents to prevent duplicate storage and remove
  // default parameter values.
  if (isset($parameters['expanded'])) {
    sort($parameters['expanded']);
  }
  $tree_cid = 'links:' . $menu_name . ':tree-data:' . $language_interface->id . ':' . hash('sha256', serialize($parameters));

  // If we do not have this tree in the static cache, check {cache_menu}.
  if (!isset($trees[$tree_cid])) {
    $cache = cache('menu')->get($tree_cid);
    if ($cache && isset($cache->data)) {
      $trees[$tree_cid] = $cache->data;
    }
  }

  if (!isset($trees[$tree_cid])) {
    $query = \Drupal::entityQuery('menu_link');
    for ($i = 1; $i <= MENU_MAX_DEPTH; $i++) {
      $query->sort('p' . $i, 'ASC');
    }
    $query->condition('menu_name', $menu_name);
    if (!empty($parameters['expanded'])) {
      $query->condition('plid', $parameters['expanded'], 'IN');
    }
    elseif (!empty($parameters['only_active_trail'])) {
      $query->condition('mlid', $parameters['active_trail'], 'IN');
    }
    $min_depth = (isset($parameters['min_depth']) ? $parameters['min_depth'] : 1);
    if ($min_depth != 1) {
      $query->condition('depth', $min_depth, '>=');
    }
    if (isset($parameters['max_depth'])) {
      $query->condition('depth', $parameters['max_depth'], '<=');
    }
    // Add custom query conditions, if any were passed.
    if (isset($parameters['conditions'])) {
      foreach ($parameters['conditions'] as $column => $value) {
        $query->condition($column, $value);
      }
    }

    // Build an ordered array of links using the query result object.
    $links = array();
    if ($result = $query->execute()) {
      $links = menu_link_load_multiple($result);
    }
    $active_trail = (isset($parameters['active_trail']) ? $parameters['active_trail'] : array());
    $data['tree'] = menu_tree_data($links, $active_trail, $min_depth);
    $data['node_links'] = array();
    menu_tree_collect_node_links($data['tree'], $data['node_links']);

    // Cache the data, if it is not already in the cache.
    cache('menu')->set($tree_cid, $data, CacheBackendInterface::CACHE_PERMANENT, array('menu' => $menu_name));
    $trees[$tree_cid] = $data;
  }

  return $trees[$tree_cid];
}

/**
 * Collects node links from a given menu tree recursively.
 *
 * @param $tree
 *   The menu tree you wish to collect node links from.
 * @param $node_links
 *   An array in which to store the collected node links.
 */
function menu_tree_collect_node_links(&$tree, &$node_links) {
  foreach ($tree as $key => $v) {
    if ($tree[$key]['link']['router_path'] == 'node/%') {
      $nid = substr($tree[$key]['link']['link_path'], 5);
      if (is_numeric($nid)) {
        $node_links[$nid][$tree[$key]['link']['mlid']] = &$tree[$key]['link'];
        $tree[$key]['link']['access'] = FALSE;
      }
    }
    if ($tree[$key]['below']) {
      menu_tree_collect_node_links($tree[$key]['below'], $node_links);
    }
  }
}

/**
 * Checks access and performs dynamic operations for each link in the tree.
 *
 * @param $tree
 *   The menu tree you wish to operate on.
 * @param $node_links
 *   A collection of node link references generated from $tree by
 *   menu_tree_collect_node_links().
 */
function menu_tree_check_access(&$tree, $node_links = array()) {
  if ($node_links) {
    $nids = array_keys($node_links);
    $select = db_select('node_field_data', 'n');
    $select->addField('n', 'nid');
    // @todo This should be actually filtering on the desired node status field
    //   language and just fall back to the default language.
    $select->condition('n.status', 1);

    $select->condition('n.nid', $nids, 'IN');
    $select->addTag('node_access');
    $nids = $select->execute()->fetchCol();
    foreach ($nids as $nid) {
      foreach ($node_links[$nid] as $mlid => $link) {
        $node_links[$nid][$mlid]['access'] = TRUE;
      }
    }
  }
  _menu_tree_check_access($tree);
}

/**
 * Sorts the menu tree and recursively checks access for each item.
 */
function _menu_tree_check_access(&$tree) {
  $new_tree = array();
  foreach ($tree as $key => $v) {
    $item = &$tree[$key]['link'];
    _menu_link_translate($item);
    if ($item['access'] || ($item['in_active_trail'] && strpos($item['href'], '%') !== FALSE)) {
      if ($tree[$key]['below']) {
        _menu_tree_check_access($tree[$key]['below']);
      }
      // The weights are made a uniform 5 digits by adding 50000 as an offset.
      // After _menu_link_translate(), $item['title'] has the localized link title.
      // Adding the mlid to the end of the index insures that it is unique.
      $new_tree[(50000 + $item['weight']) . ' ' . $item['title'] . ' ' . $item['mlid']] = $tree[$key];
    }
  }
  // Sort siblings in the tree based on the weights and localized titles.
  ksort($new_tree);
  $tree = $new_tree;
}

/**
 * Sorts and returns the built data representing a menu tree.
 *
 * @param $links
 *   A flat array of menu links that are part of the menu. Each array element
 *   is an associative array of information about the menu link, containing the
 *   fields from the {menu_links} table, and optionally additional information
 *   from the {menu_router} table, if the menu item appears in both tables.
 *   This array must be ordered depth-first. See _menu_build_tree() for a sample
 *   query.
 * @param $parents
 *   An array of the menu link ID values that are in the path from the current
 *   page to the root of the menu tree.
 * @param $depth
 *   The minimum depth to include in the returned menu tree.
 *
 * @return
 *   An array of menu links in the form of a tree. Each item in the tree is an
 *   associative array containing:
 *   - link: The menu link item from $links, with additional element
 *     'in_active_trail' (TRUE if the link ID was in $parents).
 *   - below: An array containing the sub-tree of this item, where each element
 *     is a tree item array with 'link' and 'below' elements. This array will be
 *     empty if the menu item has no items in its sub-tree having a depth
 *     greater than or equal to $depth.
 */
function menu_tree_data(array $links, array $parents = array(), $depth = 1) {
  // Reverse the array so we can use the more efficient array_pop() function.
  $links = array_reverse($links);
  return _menu_tree_data($links, $parents, $depth);
}

/**
 * Builds the data representing a menu tree.
 *
 * The function is a bit complex because the rendering of a link depends on
 * the next menu link.
 */
function _menu_tree_data(&$links, $parents, $depth) {
  $tree = array();
  while ($item = array_pop($links)) {
    // We need to determine if we're on the path to root so we can later build
    // the correct active trail.
    $item['in_active_trail'] = in_array($item['mlid'], $parents);
    // Add the current link to the tree.
    $tree[$item['mlid']] = array(
      'link' => $item,
      'below' => array(),
    );
    // Look ahead to the next link, but leave it on the array so it's available
    // to other recursive function calls if we return or build a sub-tree.
    $next = end($links);
    // Check whether the next link is the first in a new sub-tree.
    if ($next && $next['depth'] > $depth) {
      // Recursively call _menu_tree_data to build the sub-tree.
      $tree[$item['mlid']]['below'] = _menu_tree_data($links, $parents, $next['depth']);
      // Fetch next link after filling the sub-tree.
      $next = end($links);
    }
    // Determine if we should exit the loop and return.
    if (!$next || $next['depth'] < $depth) {
      break;
    }
  }
  return $tree;
}

/**
 * Implements template_preprocess_HOOK() for theme_menu_tree().
 */
function template_preprocess_menu_tree(&$variables) {
  $variables['tree'] = $variables['tree']['#children'];
}

/**
 * Returns HTML for a wrapper for a menu sub-tree.
 *
 * @param $variables
 *   An associative array containing:
 *   - tree: An HTML string containing the tree's items.
 *
 * @see template_preprocess_menu_tree()
 * @ingroup themeable
 */
function theme_menu_tree($variables) {
  return '<ul class="menu">' . $variables['tree'] . '</ul>';
}

/**
 * Returns HTML for a menu link and submenu.
 *
 * @param $variables
 *   An associative array containing:
 *   - element: Structured array data for a menu link.
 *
 * @ingroup themeable
 */
function theme_menu_link(array $variables) {
  $element = $variables['element'];
  $sub_menu = '';

  if ($element['#below']) {
    $sub_menu = drupal_render($element['#below']);
  }
  $output = l($element['#title'], $element['#href'], $element['#localized_options']);
  return '<li' . new Attribute($element['#attributes']) . '>' . $output . $sub_menu . "</li>\n";
}

/**
 * Returns HTML for a single local task link.
 *
 * @param $variables
 *   An associative array containing:
 *   - element: A render element containing:
 *     - #link: A menu link array with 'title', 'href', and 'localized_options'
 *       keys.
 *     - #active: A boolean indicating whether the local task is active.
 *
 * @ingroup themeable
 */
function theme_menu_local_task($variables) {
  $link = $variables['element']['#link'];
  $link += array(
    'localized_options' => array(),
  );
  $link_text = $link['title'];

  if (!empty($variables['element']['#active'])) {
    // Add text to indicate active tab for non-visual users.
    $active = '<span class="visually-hidden">' . t('(active tab)') . '</span>';

    // If the link does not contain HTML already, String::checkPlain() it now.
    // After we set 'html'=TRUE the link will not be sanitized by l().
    if (empty($link['localized_options']['html'])) {
      $link['title'] = String::checkPlain($link['title']);
    }
    $link['localized_options']['html'] = TRUE;
    $link_text = t('!local-task-title!active', array('!local-task-title' => $link['title'], '!active' => $active));
  }
  if (!empty($link['href'])) {
    // @todo - remove this once all pages are converted to routes.
    $a_tag = l($link_text, $link['href'], $link['localized_options']);
  }
  else {
    $a_tag = \Drupal::l($link_text, $link['route_name'], $link['route_parameters'], $link['localized_options']);
  }

  return '<li' . (!empty($variables['element']['#active']) ? ' class="active"' : '') . '>' . $a_tag . '</li>';
}

/**
 * Returns HTML for a single local action link.
 *
 * @param $variables
 *   An associative array containing:
 *   - element: A render element containing:
 *     - #link: A menu link array with 'title', 'href', and 'localized_options'
 *       keys.
 *
 * @ingroup themeable
 */
function theme_menu_local_action($variables) {
  $link = $variables['element']['#link'];
  $link += array(
    'href' => '',
    'localized_options' => array(),
    'route_parameters' => array(),
  );
  $link['localized_options']['attributes']['class'][] = 'button';
  $link['localized_options']['attributes']['class'][] = 'button-action';

  $output = '<li>';
  // @todo Remove this check and the call to l() when all pages are converted to
  //   routes.
  // @todo Figure out how to support local actions without a href properly.
  if ($link['href'] === '' && !empty($link['route_name'])) {
    $output .= Drupal::l($link['title'], $link['route_name'], $link['route_parameters'], $link['localized_options']);
  }
  else {
    $output .= l($link['title'], $link['href'], $link['localized_options']);
  }
  $output .= "</li>";

  return $output;
}

/**
 * Generates elements for the $arg array in the help hook.
 */
function drupal_help_arg($arg = array()) {
  // Note - the number of empty elements should be > MENU_MAX_PARTS.
  return $arg + array('', '', '', '', '', '', '', '', '', '', '', '');
}

/**
 * Returns an array containing the names of system-defined (default) menus.
 */
function menu_list_system_menus() {
  return array(
    'tools' => 'Tools',
    'admin' => 'Administration',
    'account' => 'User account menu',
    'main' => 'Main navigation',
    'footer' => 'Footer menu',
  );
}

/**
 * Returns an array of links to be rendered as the Main menu.
 */
function menu_main_menu() {
  $config = \Drupal::config('menu.settings');
  $menu_enabled = module_exists('menu');
  // When menu module is not enabled, we need a hardcoded default value.
  $main_links_source = $menu_enabled ? $config->get('main_links') : 'main';
  return menu_navigation_links($main_links_source);
}

/**
 * Returns an array of links to be rendered as the Secondary links.
 */
function menu_secondary_menu() {
  $config = \Drupal::config('menu.settings');
  $menu_enabled = module_exists('menu');
  // When menu module is not enabled, we need a hardcoded default value.
  $main_links_source = $menu_enabled ? $config->get('main_links') : 'main';
  $secondary_links_source = $menu_enabled ? $config->get('secondary_links') : 'account';

  // If the secondary menu source is set as the primary menu, we display the
  // second level of the primary menu.
  if ($secondary_links_source == $main_links_source) {
    return menu_navigation_links($main_links_source, 1);
  }
  else {
    return menu_navigation_links($secondary_links_source, 0);
  }
}

/**
 * Returns an array of links for a navigation menu.
 *
 * @param $menu_name
 *   The name of the menu.
 * @param $level
 *   Optional, the depth of the menu to be returned.
 *
 * @return
 *   An array of links of the specified menu and level.
 */
function menu_navigation_links($menu_name, $level = 0) {
  // Don't even bother querying the menu table if no menu is specified.
  if (empty($menu_name)) {
    return array();
  }

  // Get the menu hierarchy for the current page.
  $tree = menu_tree_page_data($menu_name, $level + 1);

  // Go down the active trail until the right level is reached.
  while ($level-- > 0 && $tree) {
    // Loop through the current level's items until we find one that is in trail.
    while ($item = array_shift($tree)) {
      if ($item['link']['in_active_trail']) {
        // If the item is in the active trail, we continue in the subtree.
        $tree = empty($item['below']) ? array() : $item['below'];
        break;
      }
    }
  }

  // Create a single level of links.
  $router_item = menu_get_item();
  $links = array();
  foreach ($tree as $item) {
    if (!$item['link']['hidden']) {
      $class = '';
      $l = $item['link']['localized_options'];
      $l['href'] = $item['link']['href'];
      $l['title'] = $item['link']['title'];
      if ($item['link']['in_active_trail']) {
        $class = ' active-trail';
        $l['attributes']['class'][] = 'active-trail';
      }
      // Normally, l() compares the href of every link with the current path and
      // sets the active class accordingly. But local tasks do not appear in
      // menu trees, so if the current path is a local task, and this link is
      // its tab root, then we have to set the class manually.
      if ($item['link']['href'] == $router_item['tab_root_href'] && $item['link']['href'] != current_path()) {
        $l['attributes']['class'][] = 'active';
      }
      // Keyed with the unique mlid to generate classes in theme_links().
      $links['menu-' . $item['link']['mlid'] . $class] = $l;
    }
  }
  return $links;
}

/**
 * Collects the local tasks (tabs), action links, and the root path.
 *
 * @param int $level
 *   The level of tasks you ask for. Primary tasks are 0, secondary are 1.
 *
 * @return array
 *   An array containing
 *   - tabs: Local tasks for the requested level.
 *   - actions: Action links for the requested level.
 *   - root_path: The router path for the current page. If the current page is
 *     a default local task, then this corresponds to the parent tab.
 *
 * @see hook_menu_local_tasks()
 * @see hook_menu_local_tasks_alter()
 */
function menu_local_tasks($level = 0) {
  $data = &drupal_static(__FUNCTION__);
  $root_path = &drupal_static(__FUNCTION__ . ':root_path', '');
  $empty = array(
    'tabs' => array(),
    'actions' => array(),
    'root_path' => &$root_path,
  );

  if (!isset($data)) {
    // Look for route-based tabs.
    $data['tabs'] = array();
    $data['actions'] = array();

    $route_name = \Drupal::request()->attributes->get(RouteObjectInterface::ROUTE_NAME);
    if (!empty($route_name)) {
      $manager = \Drupal::service('plugin.manager.menu.local_task');
      $local_tasks = $manager->getTasksBuild($route_name);
      foreach ($local_tasks as $level => $items) {
        $data['tabs'][$level] = empty($data['tabs'][$level]) ? $items : array_merge($data['tabs'][$level], $items);
      }
    }

    // @todo Remove when all local tasks/actions are converted to plugins.
    $router_item = menu_get_item();
    // If this router item points to its parent, start from the parents to
    // compute tabs and actions.
    if ($router_item && ($router_item['type'] & MENU_LINKS_TO_PARENT)) {
      $router_item = menu_get_item($router_item['tab_parent_href']);
    }
    // If we failed to fetch a router item or the current user doesn't have
    // access to it, don't bother computing the tabs.
    if ((!$route_name && !$router_item) || ($router_item && !$router_item['access'])) {
      return $empty;
    }
    if ($router_item) {
      _menu_get_legacy_tasks($router_item, $data, $root_path);
    }

    // Allow modules to dynamically add further tasks.
    $module_handler = \Drupal::moduleHandler();
    foreach ($module_handler->getImplementations('menu_local_tasks') as $module) {
      $function = $module . '_menu_local_tasks';
      $function($data, $route_name);
    }
    // Allow modules to alter local tasks.
    $module_handler->alter('menu_local_tasks', $data, $route_name);
  }

  if (isset($data['tabs'][$level])) {
    return array(
      'tabs' => $data['tabs'][$level],
      'actions' => $data['actions'],
      'root_path' => $root_path,
    );
  }
  elseif (!empty($data['actions'])) {
    return array('actions' => $data['actions']) + $empty;
  }
  return $empty;
}

/**
 * Finds legacy local tasks/actions.
 *
 * @param array $router_item
 *   The current router item.
 * @param array $data
 *   An associative array of local tasks/actions.
 * @param string $root_path
 *
 * @deprecated Remove once all local tasks/actions are converted to plugins.
 */
function _menu_get_legacy_tasks($router_item, &$data, &$root_path) {
  // Get all tabs (also known as local tasks) and the root page.
  $result = db_select('menu_router', NULL, array('fetch' => PDO::FETCH_ASSOC))
    ->fields('menu_router')
    ->condition('tab_root', $router_item['tab_root'])
    ->orderBy('weight')
    ->orderBy('title')
    ->execute();
  $map = $router_item['original_map'];
  $children = array();
  $tasks = array();
  $root_path = $router_item['path'];

  foreach ($result as $item) {
    _menu_translate($item, $map, TRUE);
    if ($item['tab_parent']) {
      // All tabs, but not the root page.
      $children[$item['tab_parent']][$item['path']] = $item;
    }
    // Store the translated item for later use.
    $tasks[$item['path']] = $item;
  }

  // Find all tabs below the current path.
  $path = $router_item['path'];
  // Tab parenting may skip levels, so the number of parts in the path may not
  // equal the depth. Thus we use the $depth counter (offset by 1000 for ksort).
  $depth = 1001;
  $tabs = array();
  $actions = array();
  while (isset($children[$path])) {
    $tabs_current = array();
    $actions_current = array();
    $next_path = '';
    $tab_count = 0;
    $action_count = 0;
    foreach ($children[$path] as $item) {
      // Local tasks can be normal items too, so bitmask with
      // MENU_IS_LOCAL_TASK before checking.
      if (!($item['type'] & MENU_IS_LOCAL_TASK)) {
        // This item is not a tab, skip it.
        continue;
      }
      if ($item['access']) {
        $link = $item;
        // The default task is always active. As tabs can be normal items
        // too, so bitmask with MENU_LINKS_TO_PARENT before checking.
        if (($item['type'] & MENU_LINKS_TO_PARENT) == MENU_LINKS_TO_PARENT) {
          // Find the first parent which is not a default local task or action.
          for ($p = $item['tab_parent']; ($tasks[$p]['type'] & MENU_LINKS_TO_PARENT) == MENU_LINKS_TO_PARENT; $p = $tasks[$p]['tab_parent']);
          // Use the path of the parent instead.
          $link['href'] = $tasks[$p]['href'];
          // Mark the link as active, if the current path happens to be the
          // path of the default local task itself (i.e., instead of its
          // tab_parent_href or tab_root_href). Normally, links for default
          // local tasks link to their parent, but the path of default local
          // tasks can still be accessed directly, in which case this link
          // would not be marked as active, since l() only compares the href
          // with current_path().
          if ($link['href'] != current_path()) {
            $link['localized_options']['attributes']['class'][] = 'active';
          }
          $tabs_current[$link['href']] = array(
            '#theme' => 'menu_local_task',
            '#link' => $link,
            '#active' => TRUE,
            '#weight' => isset($link['weight']) ? $link['weight'] : NULL,
          );
          $next_path = $item['path'];
          $tab_count++;
        }
        else {
          $tabs_current[$link['href']] = array(
            '#theme' => 'menu_local_task',
            '#link' => $link,
            '#weight' => isset($link['weight']) ? $link['weight'] : NULL,
          );
          $tab_count++;
        }
      }
    }
    $path = $next_path;
    $tabs[$depth] = $tabs_current;
    $actions = array_merge($actions, $actions_current);
    $depth++;
  }
  $data['actions'] = $actions;
  // Find all tabs at the same level or above the current one.
  $parent = $router_item['tab_parent'];
  $path = $router_item['path'];
  $current = $router_item;
  $depth = 1000;
  while (isset($children[$parent])) {
    $tabs_current = array();
    $next_path = '';
    $next_parent = '';
    $count = 0;
    foreach ($children[$parent] as $item) {
      if ($item['access']) {
        $count++;
        $link = $item;
        // Local tasks can be normal items too, so bitmask with
        // MENU_LINKS_TO_PARENT before checking.
        if (($item['type'] & MENU_LINKS_TO_PARENT) == MENU_LINKS_TO_PARENT) {
          // Find the first parent which is not a default local task.
          for ($p = $item['tab_parent']; ($tasks[$p]['type'] & MENU_LINKS_TO_PARENT) == MENU_LINKS_TO_PARENT; $p = $tasks[$p]['tab_parent']);
          // Use the path of the parent instead.
          $link['href'] = $tasks[$p]['href'];
          if ($item['path'] == $router_item['path']) {
            $root_path = $tasks[$p]['path'];
          }
        }
        // We check for the active tab.
        if ($item['path'] == $path) {
          // Mark the link as active, if the current path is a (second-level)
          // local task of a default local task. Since this default local task
          // links to its parent, l() will not mark it as active, as it only
          // compares the link's href to current_path().
          if ($link['href'] != current_path()) {
            $link['localized_options']['attributes']['class'][] = 'active';
          }
          $tabs_current[$link['href']] = array(
            '#theme' => 'menu_local_task',
            '#link' => $link,
            '#active' => TRUE,
            '#weight' => isset($link['weight']) ? $link['weight'] : NULL,
          );
          $next_path = $item['tab_parent'];
          if (isset($tasks[$next_path])) {
            $next_parent = $tasks[$next_path]['tab_parent'];
          }
        }
        else {
          $tabs_current[$link['href']] = array(
            '#theme' => 'menu_local_task',
            '#link' => $link,
            '#weight' => isset($link['weight']) ? $link['weight'] : NULL,
          );
        }
      }
    }
    $path = $next_path;
    $parent = $next_parent;
    $tabs[$depth] = $tabs_current;
    $depth--;
  }
  // Sort by depth.
  ksort($tabs);
  // Remove the depth, we are interested only in their relative placement.
  $tabs = array_values($tabs);
  $data['tabs'] += $tabs;
}

/**
 * Returns the rendered local tasks at the top level.
 */
function menu_primary_local_tasks() {
  $links = menu_local_tasks(0);
  // Do not display single tabs.
  return count(element_get_visible_children($links['tabs'])) > 1 ? $links['tabs'] : '';
}

/**
 * Returns the rendered local tasks at the second level.
 */
function menu_secondary_local_tasks() {
  $links = menu_local_tasks(1);
  // Do not display single tabs.
  return count(element_get_visible_children($links['tabs'])) > 1 ? $links['tabs'] : '';
}

/**
 * Returns the rendered local actions at the current level.
 */
function menu_get_local_actions() {
  $links = menu_local_tasks();
  $route_name = Drupal::request()->attributes->get(RouteObjectInterface::ROUTE_NAME);
  $manager = \Drupal::service('plugin.manager.menu.local_action');
  return $manager->getActionsForRoute($route_name) + $links['actions'];
}

/**
 * Returns the router path, or the path for a default local task's parent.
 */
function menu_tab_root_path() {
  $links = menu_local_tasks();
  return $links['root_path'];
}

/**
 * Returns a renderable element for the primary and secondary tabs.
 */
function menu_local_tabs() {
  $build = array(
    '#theme' => 'menu_local_tasks',
    '#primary' => menu_primary_local_tasks(),
    '#secondary' => menu_secondary_local_tasks(),
  );
  return !empty($build['#primary']) || !empty($build['#secondary']) ? $build : array();
}

/**
 * Returns HTML for primary and secondary local tasks.
 *
 * @param $variables
 *   An associative array containing:
 *     - primary: (optional) An array of local tasks (tabs).
 *     - secondary: (optional) An array of local tasks (tabs).
 *
 * @ingroup themeable
 * @see menu_local_tasks()
 */
function theme_menu_local_tasks(&$variables) {
  $output = '';

  if (!empty($variables['primary'])) {
    $variables['primary']['#prefix'] = '<h2 class="visually-hidden">' . t('Primary tabs') . '</h2>';
    $variables['primary']['#prefix'] .= '<ul class="tabs primary">';
    $variables['primary']['#suffix'] = '</ul>';
    $output .= drupal_render($variables['primary']);
  }
  if (!empty($variables['secondary'])) {
    $variables['secondary']['#prefix'] = '<h2 class="visually-hidden">' . t('Secondary tabs') . '</h2>';
    $variables['secondary']['#prefix'] .= '<ul class="tabs secondary">';
    $variables['secondary']['#suffix'] = '</ul>';
    $output .= drupal_render($variables['secondary']);
  }

  return $output;
}

/**
 * Sets (or gets) the active menu for the current page.
 *
 * The active menu for the page determines the active trail.
 *
 * @return
 *   An array of menu machine names, in order of preference. The
 *   'system.menu.active_menus_default' config item may be used to assert a menu
 *   order different from the order of creation, or to prevent a particular menu
 *   from being used at all in the active trail.
 *   E.g., $conf['system.menu']['active_menus_default'] = array('tools',
 *   'main').
 */
function menu_set_active_menu_names($menu_names = NULL) {
  $active = &drupal_static(__FUNCTION__);

  if (isset($menu_names) && is_array($menu_names)) {
    $active = $menu_names;
  }
  elseif (!isset($active)) {
    $config = \Drupal::config('system.menu');
    $active = $config->get('active_menus_default') ?: array_keys(menu_list_system_menus());
  }
  return $active;
}

/**
 * Gets the active menu for the current page.
 */
function menu_get_active_menu_names() {
  return menu_set_active_menu_names();
}

/**
 * Sets the active path, which determines which page is loaded.
 *
 * Note that this may not have the desired effect unless invoked very early
 * in the page load or unless you do a subrequest to generate your page output.
 *
 * @param $path
 *   A Drupal path - not a path alias.
 */
function menu_set_active_item($path) {
  // Since the active item has changed, the active menu trail may also be out
  // of date.
  drupal_static_reset('menu_set_active_trail');
  // @todo Refactor to use the Symfony Request object.
  _current_path($path);
}

/**
 * Sets the active trail (path to the menu tree root) of the current page.
 *
 * Any trail set by this function will only be used for functionality that calls
 * menu_get_active_trail(). Drupal core only uses trails set here for
 * the page title and not for menu trees or page content.
 *
 * To affect the trail used by menu trees, use menu_tree_set_path(). To affect
 * the page content, use menu_set_active_item() instead.
 *
 * @param $new_trail
 *   Menu trail to set; the value is saved in a static variable and can be
 *   retrieved by menu_get_active_trail(). The format of this array should be
 *   the same as the return value of menu_get_active_trail().
 *
 * @return
 *   The active trail. See menu_get_active_trail() for details.
 */
function menu_set_active_trail($new_trail = NULL) {
  $trail = &drupal_static(__FUNCTION__);

  if (isset($new_trail)) {
    $trail = $new_trail;
  }
  elseif (!isset($trail)) {
    $trail = array();
    $trail[] = array(
      'title' => t('Home'),
      'href' => '<front>',
      'link_path' => '',
      'localized_options' => array(),
      'type' => 0,
    );

    // Try to retrieve a menu link corresponding to the current path. If more
    // than one exists, the link from the most preferred menu is returned.
    $preferred_link = menu_link_get_preferred();
    $current_item = menu_get_item();

    // There is a link for the current path.
    if ($preferred_link) {
      // Pass TRUE for $only_active_trail to make menu_tree_page_data() build
      // a stripped down menu tree containing the active trail only, in case
      // the given menu has not been built in this request yet.
      $tree = menu_tree_page_data($preferred_link['menu_name'], NULL, TRUE);
      list($key, $curr) = each($tree);
    }
    // There is no link for the current path.
    else {
      $preferred_link = $current_item;
      $curr = FALSE;
    }

    while ($curr) {
      $link = $curr['link'];
      if ($link['in_active_trail']) {
        // Add the link to the trail, unless it links to its parent.
        if (!($link['type'] & MENU_LINKS_TO_PARENT)) {
          // The menu tree for the active trail may contain additional links
          // that have not been translated yet, since they contain dynamic
          // argument placeholders (%). Such links are not contained in regular
          // menu trees, and have only been loaded for the additional
          // translation that happens here, so as to be able to display them in
          // the breadcumb for the current page.
          // @see _menu_tree_check_access()
          // @see _menu_link_translate()
          if (strpos($link['href'], '%') !== FALSE) {
            _menu_link_translate($link, TRUE);
          }
          if ($link['access']) {
            $trail[] = $link;
          }
        }
        $tree = $curr['below'] ? $curr['below'] : array();
      }
      list($key, $curr) = each($tree);
    }
    // Make sure the current page is in the trail to build the page title, by
    // appending either the preferred link or the menu router item for the
    // current page. Exclude it if we are on the front page.
    $last = end($trail);
    if ($preferred_link && $last['href'] != $preferred_link['href'] && !drupal_is_front_page()) {
      $trail[] = $preferred_link;
    }
  }
  return $trail;
}

/**
 * Looks up the preferred menu link for a given system path.
 *
 * @param $path
 *   The path; for example, 'node/5'. The function will find the corresponding
 *   menu link ('node/5' if it exists, or fallback to 'node/%').
 * @param $selected_menu
 *   The name of a menu used to restrict the search for a preferred menu link.
 *   If not specified, all the menus returned by menu_get_active_menu_names()
 *   will be used.
 *
 * @return
 *   A fully translated menu link, or FALSE if no matching menu link was
 *   found. The most specific menu link ('node/5' preferred over 'node/%') in
 *   the most preferred menu (as defined by menu_get_active_menu_names()) is
 *   returned.
 */
function menu_link_get_preferred($path = NULL, $selected_menu = NULL) {
  $preferred_links = &drupal_static(__FUNCTION__);

  if (!isset($path)) {
    $path = current_path();
  }

  if (empty($selected_menu)) {
    // Use an illegal menu name as the key for the preferred menu link.
    $selected_menu = MENU_PREFERRED_LINK;
  }

  if (!isset($preferred_links[$path])) {
    // Look for the correct menu link by building a list of candidate paths,
    // which are ordered by priority (translated hrefs are preferred over
    // untranslated paths). Afterwards, the most relevant path is picked from
    // the menus, ordered by menu preference.
    $item = menu_get_item($path);
    $path_candidates = array();
    // 1. The current item href.
    $path_candidates[$item['href']] = $item['href'];
    // 2. The tab root href of the current item (if any).
    if ($item['tab_parent'] && ($tab_root = menu_get_item($item['tab_root_href']))) {
      $path_candidates[$tab_root['href']] = $tab_root['href'];
    }
    // 3. The current item path (with wildcards).
    $path_candidates[$item['path']] = $item['path'];
    // 4. The tab root path of the current item (if any).
    if (!empty($tab_root)) {
      $path_candidates[$tab_root['path']] = $tab_root['path'];
    }

    // Retrieve a list of menu names, ordered by preference.
    $menu_names = menu_get_active_menu_names();
    // Put the selected menu at the front of the list.
    array_unshift($menu_names, $selected_menu);

    $menu_links = entity_load_multiple_by_properties('menu_link', array('link_path' => $path_candidates));

    // Sort candidates by link path and menu name.
    $candidates = array();
    foreach ($menu_links as $candidate) {
      $candidates[$candidate['link_path']][$candidate['menu_name']] = $candidate;
      // Add any menus not already in the menu name search list.
      if (!in_array($candidate['menu_name'], $menu_names)) {
        $menu_names[] = $candidate['menu_name'];
      }
    }

    // Store the most specific link for each menu. Also save the most specific
    // link of the most preferred menu in $preferred_link.
    foreach ($path_candidates as $link_path) {
      if (isset($candidates[$link_path])) {
        foreach ($menu_names as $menu_name) {
          if (empty($preferred_links[$path][$menu_name]) && isset($candidates[$link_path][$menu_name])) {
            $candidate_item = $candidates[$link_path][$menu_name];
            $map = explode('/', $path);
            _menu_translate($candidate_item, $map);
            if ($candidate_item['access']) {
              $preferred_links[$path][$menu_name] = $candidate_item;
              if (empty($preferred_links[$path][MENU_PREFERRED_LINK])) {
                // Store the most specific link.
                $preferred_links[$path][MENU_PREFERRED_LINK] = $candidate_item;
              }
            }
          }
        }
      }
    }
  }

  return isset($preferred_links[$path][$selected_menu]) ? $preferred_links[$path][$selected_menu] : FALSE;
}

/**
 * Gets the active trail (path to root menu root) of the current page.
 *
 * If a trail is supplied to menu_set_active_trail(), that value is returned. If
 * a trail is not supplied to menu_set_active_trail(), the path to the current
 * page is calculated and returned. The calculated trail is also saved as a
 * static value for use by subsequent calls to menu_get_active_trail().
 *
 * @return
 *   Path to menu root of the current page, as an array of menu link items,
 *   starting with the site's home page. Each link item is an associative array
 *   with the following components:
 *   - title: Title of the item.
 *   - href: Drupal path of the item.
 *   - localized_options: Options for passing into the l() function.
 *   - type: A menu type constant, such as MENU_DEFAULT_LOCAL_TASK, or 0 to
 *     indicate it's not really in the menu (used for the home page item).
 */
function menu_get_active_trail() {
  return menu_set_active_trail();
}

/**
 * Gets the title of the current page, as determined by the active trail.
 */
function menu_get_active_title() {
  $active_trail = menu_get_active_trail();

  foreach (array_reverse($active_trail) as $item) {
    if (!(bool) ($item['type'] & MENU_IS_LOCAL_TASK)) {
      return $item['title'];
    }
  }
}

/**
 * Clears the cached cached data for a single named menu.
 */
function menu_cache_clear($menu_name = 'tools') {
  cache('menu')->deleteTags(array('menu' => $menu_name));
  // Also clear the menu system static caches.
  menu_reset_static_cache();
}

/**
 * Clears all cached menu data.
 *
 * This should be called any time broad changes
 * might have been made to the router items or menu links.
 */
function menu_cache_clear_all() {
  cache('menu')->deleteAll();
  menu_reset_static_cache();
}

/**
 * Resets the menu system static cache.
 */
function menu_reset_static_cache() {
  \Drupal::entityManager()
    ->getStorageController('menu_link')->resetCache();
  drupal_static_reset('_menu_build_tree');
  drupal_static_reset('menu_tree');
  drupal_static_reset('menu_tree_all_data');
  drupal_static_reset('menu_tree_page_data');
  drupal_static_reset('menu_link_get_preferred');
}

/**
 * Populates the database tables used by various menu functions.
 *
 * This function will clear and populate the {menu_router} table, add entries
 * to {menu_links} for new router items, and then remove stale items from
 * {menu_links}.
 *
 * @return
 *   TRUE if the menu was rebuilt, FALSE if another thread was rebuilding
 *   in parallel and the current thread just waited for completion.
 */
function menu_router_rebuild() {
  if (!lock()->acquire(__FUNCTION__)) {
    // Wait for another request that is already doing this work.
    // We choose to block here since otherwise the router item may not
    // be available during routing resulting in a 404.
    lock()->wait(__FUNCTION__);
    return FALSE;
  }

  $transaction = db_transaction();

  try {
    list($menu) = menu_router_build(TRUE);
    _menu_navigation_links_rebuild($menu);
    // Clear the menu, page and block caches.
    menu_cache_clear_all();
    _menu_clear_page_cache();
    // Indicate that the menu has been successfully rebuilt.
    \Drupal::state()->delete('menu_rebuild_needed');
  }
  catch (Exception $e) {
    $transaction->rollback();
    watchdog_exception('menu', $e);
  }

  lock()->release(__FUNCTION__);
  return TRUE;
}

/**
 * Collects and alters the menu definitions.
 *
 * @param bool $save
 *   (optional) Save the new router to the database. Defaults to FALSE.
 */
function menu_router_build($save = FALSE) {
  // Ensure that all configuration used to build the menu items are loaded
  // without overrides.
  config_context_enter('config.context.free');
  // We need to manually call each module so that we can know which module
  // a given item came from.
  $callbacks = array();
  foreach (\Drupal::moduleHandler()->getImplementations('menu') as $module) {
    $router_items = call_user_func($module . '_menu');
    if (isset($router_items) && is_array($router_items)) {
      foreach (array_keys($router_items) as $path) {
        $router_items[$path]['module'] = $module;
      }
      $callbacks = array_merge($callbacks, $router_items);
    }
  }
  // Alter the menu as defined in modules, keys are like user/%user.
  drupal_alter('menu', $callbacks);
  // Return to the original context before menu building.
  config_context_leave();
  foreach ($callbacks as $path => $router_item) {
    // If the menu item is a default local task and incorrectly references a
    // route, remove it.
    // @todo This may be removed later depending on the outcome of
    // http://drupal.org/node/1889790
    if (isset($router_item['type']) && $router_item['type'] == MENU_DEFAULT_LOCAL_TASK) {
      unset($callbacks[$path]['route_name']);
    }
    // If the menu item references a route, normalize the route information
    // into the old structure. Note that routes are keyed by name, not path,
    // so the path of the route takes precedence.
    if (isset($router_item['route_name'])) {
      $router_item['page callback'] = 'USES_ROUTE';
      $router_item['access callback'] = TRUE;
      $new_path = _menu_router_translate_route($router_item['route_name']);

      unset($callbacks[$path]);
      $callbacks[$new_path] = $router_item;
    }
  }
  list($menu, $masks) = _menu_router_build($callbacks, $save);
  _menu_router_cache($menu);

  return array($menu, $masks);
}

/**
 * Translates a route name to its router item path.
 *
 * @param string $route_name
 *   The route name to translate.
 *
 * @return string
 *   The translated path pattern from the route.
 */
function _menu_router_translate_route($route_name) {
  $outline = \Drupal::service('router.route_provider')
    ->getRouteByName($route_name)
    ->compile()
    ->getPatternOutline();
  return trim($outline, '/');
}

/**
 * Stores the menu router if we have it in memory.
 */
function _menu_router_cache($new_menu = NULL) {
  $menu = &drupal_static(__FUNCTION__);

  if (isset($new_menu)) {
    $menu = $new_menu;
  }
  return $menu;
}

/**
 * Gets the menu router.
 */
function menu_get_router() {
  // Check first if we have it in memory already.
  $menu = _menu_router_cache();
  if (empty($menu)) {
    list($menu) = menu_router_build();
  }
  return $menu;
}

/**
 * Builds menu links for the items in the menu router.
 *
 * @todo This function should be removed/refactored.
 */
function _menu_navigation_links_rebuild($menu) {
  if (!\Drupal::moduleHandler()->moduleExists('menu_link')) {
    // The Menu link module may not be available during install, so rebuild
    // when possible.
    return;
  }
  $menu_link_controller = \Drupal::entityManager()
    ->getStorageController('menu_link');

  // Add normal and suggested items as links.
  $router_items = array();
  foreach ($menu as $path => $router_item) {
    if ($router_item['_visible']) {
      $router_items[$path] = $router_item;
      $sort[$path] = $router_item['_number_parts'];
    }
  }
  if ($router_items) {
    // Keep an array of processed menu links, to allow
    // Drupal\menu_link\MenuLinkStorageController::save() to check this for
    // parents instead of querying the database.
    $parent_candidates = array();
    // Make sure no child comes before its parent.
    array_multisort($sort, SORT_NUMERIC, $router_items);

    foreach ($router_items as $key => $router_item) {
      // For performance reasons, do a straight query now and convert to a menu
      // link entity later.
      // @todo revisit before release.
      $existing_item = db_select('menu_links')
        ->fields('menu_links')
        ->condition('link_path', $router_item['path'])
        ->condition('module', 'system')
        ->execute()->fetchAll();
      if ($existing_item) {
        $existing_item = reset($existing_item);
        $existing_item->options = unserialize($existing_item->options);
        $existing_item->route_parameters = unserialize($existing_item->route_parameters);

        $router_item['mlid'] = $existing_item->mlid;
        $router_item['uuid'] = $existing_item->uuid;
        // A change in hook_menu may move the link to a different menu
        if (empty($router_item['menu_name']) || ($router_item['menu_name'] == $existing_item->menu_name)) {
          $router_item['menu_name'] = $existing_item->menu_name;
          $router_item['plid'] = $existing_item->plid;
        }
        else {
          // It moved to a new menu.
          // Let Drupal\menu_link\MenuLinkStorageController::save() try to find
          // a new parent based on the path.
          unset($router_item['plid']);
        }
        $router_item['has_children'] = $existing_item->has_children;
        $router_item['updated'] = $existing_item->updated;

        // Convert the existing item to a typed object.
        $existing_item = $menu_link_controller->create(get_object_vars($existing_item));
      }
      else {
        $existing_item = NULL;
      }

      if ($existing_item && $existing_item->customized) {
        $parent_candidates[$existing_item->mlid] = $existing_item;
      }
      else {
        $menu_link = MenuLink::buildFromRouterItem($router_item);
        $menu_link->original = $existing_item;
        $menu_link->parentCandidates = $parent_candidates;
        $menu_link_controller->save($menu_link);
        $parent_candidates[$menu_link->id()] = $menu_link;
        unset($router_items[$key]);
      }
    }
  }

  $paths = array_keys($menu);
  // Updated and customized items whose router paths are gone need new ones.
  $menu_links = $menu_link_controller->loadUpdatedCustomized($paths);
  foreach ($menu_links as $menu_link) {
    $router_path = _menu_find_router_path($menu_link->link_path);
    if (!empty($router_path) && ($router_path != $menu_link->router_path || $menu_link->updated)) {
      // If the router path and the link path matches, it's surely a working
      // item, so we clear the updated flag.
      $updated = $menu_link->updated && $router_path != $menu_link->link_path;

      $menu_link->router_path = $router_path;
      $menu_link->updated = (int) $updated;
      $menu_link_controller->save($menu_link);
    }
  }

  // Find any item whose router path does not exist any more.
  $query = \Drupal::entityQuery('menu_link')
    ->condition('router_path', $paths, 'NOT IN')
    ->condition('external', 0)
    ->condition('updated', 0)
    ->condition('customized', 0)
    ->sort('depth', 'DESC');
  $result = $query->execute();

  // Remove all such items. Starting from those with the greatest depth will
  // minimize the amount of re-parenting done by the menu link controller.
  if (!empty($result)) {
    menu_link_delete_multiple($result, TRUE);
  }
}

/**
 * Returns an array containing all links for a menu.
 *
 * @param $menu_name
 *   The name of the menu whose links should be returned.
 *
 * @return
 *   An array of menu links.
 */
function menu_load_links($menu_name) {
  $links = array();

  $query = \Drupal::entityQuery('menu_link')
    ->condition('menu_name', $menu_name)
    // Order by weight so as to be helpful for menus that are only one level
    // deep.
    ->sort('weight');
  $result = $query->execute();

  if (!empty($result)) {
    $links = menu_link_load_multiple($result);
  }

  return $links;
}

/**
 * Deletes all links for a menu.
 *
 * @param $menu_name
 *   The name of the menu whose links will be deleted.
 */
function menu_delete_links($menu_name) {
  $links = menu_load_links($menu_name);
  menu_link_delete_multiple(array_keys($links), FALSE, TRUE);
}

/**
 * Clears the page and block caches at most twice per page load.
 */
function _menu_clear_page_cache() {
  $cache_cleared = &drupal_static(__FUNCTION__, 0);

  // Clear the page and block caches, but at most twice, including at
  //  the end of the page load when there are multiple links saved or deleted.
  if ($cache_cleared == 0) {
    cache_invalidate_tags(array('content' => TRUE));
    // Keep track of which menus have expanded items.
    _menu_set_expanded_menus();
    $cache_cleared = 1;
  }
  elseif ($cache_cleared == 1) {
    drupal_register_shutdown_function('cache_invalidate_tags', array('content' => TRUE));
    // Keep track of which menus have expanded items.
    drupal_register_shutdown_function('_menu_set_expanded_menus');
    $cache_cleared = 2;
  }
}

/**
 * Updates a list of menus with expanded items.
 */
function _menu_set_expanded_menus() {
  $names = db_query("SELECT menu_name FROM {menu_links} WHERE expanded <> 0 GROUP BY menu_name")->fetchCol();
  \Drupal::state()->set('menu_expanded', $names);
}

/**
 * Finds the router path which will serve this path.
 *
 * @param $link_path
 *  The path for we are looking up its router path.
 *
 * @return
 *  A path from $menu keys or empty if $link_path points to a nonexisting
 *  place.
 */
function _menu_find_router_path($link_path) {
  // $menu will only have data during a menu rebuild.
  $menu = _menu_router_cache();

  $router_path = $link_path;
  $parts = explode('/', $link_path, MENU_MAX_PARTS);
  $ancestors = menu_get_ancestors($parts);

  if (empty($menu)) {
    // Not during a menu rebuild, so look up in the database.
    $router_path = (string) db_select('menu_router')
      ->fields('menu_router', array('path'))
      ->condition('path', $ancestors, 'IN')
      ->orderBy('fit', 'DESC')
      ->range(0, 1)
      ->execute()->fetchField();
  }
  elseif (!isset($menu[$router_path])) {
    // Add an empty router path as a fallback.
    $ancestors[] = '';
    foreach ($ancestors as $router_path) {
      if (isset($menu[$router_path])) {
        // Exit the loop leaving $router_path as the first match.
        break;
      }
    }
    // If we did not find the path, $router_path will be the empty string
    // at the end of $ancestors.
  }
  return $router_path;
}

/**
 * Builds the router table based on the data from hook_menu().
 */
function _menu_router_build($callbacks, $save = FALSE) {
  // First pass: separate callbacks from paths, making paths ready for
  // matching. Calculate fitness, and fill some default values.
  $menu = array();
  $masks = array();
  $path_roots = array();
  foreach ($callbacks as $path => $item) {
    $load_functions = array();
    $to_arg_functions = array();
    $fit = 0;
    $move = FALSE;

    $parts = explode('/', $path, MENU_MAX_PARTS);
    $path_roots[$parts[0]] = $parts[0];
    $number_parts = count($parts);
    // We store the highest index of parts here to save some work in the fit
    // calculation loop.
    $slashes = $number_parts - 1;
    // Extract load and to_arg functions.
    foreach ($parts as $k => $part) {
      $match = FALSE;
      // Look for wildcards in the form allowed to be used in PHP functions,
      // because we are using these to construct the load function names.
      if (preg_match('/^%(|' . DRUPAL_PHP_FUNCTION_PATTERN . ')$/', $part, $matches)) {
        if (empty($matches[1])) {
          $match = TRUE;
          $load_functions[$k] = NULL;
        }
        else {
          if (function_exists($matches[1] . '_to_arg')) {
            $to_arg_functions[$k] = $matches[1] . '_to_arg';
            $load_functions[$k] = NULL;
            $match = TRUE;
          }
          if (function_exists($matches[1] . '_load')) {
            $function = $matches[1] . '_load';
            // Create an array of arguments that will be passed to the _load
            // function when this menu path is checked, if 'load arguments'
            // exists.
            $load_functions[$k] = isset($item['load arguments']) ? array($function => $item['load arguments']) : $function;
            $match = TRUE;
          }
        }
      }
      if ($match) {
        $parts[$k] = '%';
      }
      else {
        $fit |=  1 << ($slashes - $k);
      }
    }
    if ($fit) {
      $move = TRUE;
    }
    else {
      // If there is no %, it fits maximally.
      $fit = (1 << $number_parts) - 1;
    }
    $masks[$fit] = 1;
    $item['_load_functions'] = $load_functions;
    $item['to_arg_functions'] = empty($to_arg_functions) ? '' : serialize($to_arg_functions);
    $item += array(
      'title' => '',
      'type' => MENU_NORMAL_ITEM,
      'module' => '',
      '_number_parts' => $number_parts,
      '_parts' => $parts,
      '_fit' => $fit,
    );
    $item += array(
      // Default MENU_DEFAULT_LOCAL_TASKs to a weight of -10, so they appear as
      // first tab by default.
      'weight' => ($item['type'] & MENU_DEFAULT_LOCAL_TASK) == MENU_DEFAULT_LOCAL_TASK ? -10 : 0,
      '_visible' => (bool) ($item['type'] & MENU_VISIBLE_IN_BREADCRUMB),
      '_tab' => (bool) ($item['type'] & MENU_IS_LOCAL_TASK),
    );
    if ($move) {
      $new_path = implode('/', $item['_parts']);
      $menu[$new_path] = $item;
      $sort[$new_path] = $number_parts;
    }
    else {
      $menu[$path] = $item;
      $sort[$path] = $number_parts;
    }
  }
  array_multisort($sort, SORT_NUMERIC, $menu);
  // Apply inheritance rules.
  foreach ($menu as $path => $v) {
    $item = &$menu[$path];
    if (!$item['_tab']) {
      // Non-tab items.
      $item['tab_parent'] = '';
      $item['tab_root'] = $path;
    }
    // If not specified, assign the default tab type for local tasks.
    elseif (!isset($item['context'])) {
      $item['context'] = MENU_CONTEXT_PAGE;
    }
    for ($i = $item['_number_parts'] - 1; $i; $i--) {
      $parent_path = implode('/', array_slice($item['_parts'], 0, $i));
      if (isset($menu[$parent_path])) {

        $parent = &$menu[$parent_path];

        // If we have no menu name, try to inherit it from parent items.
        if (!isset($item['menu_name'])) {
          // If the parent item of this item does not define a menu name (and no
          // previous iteration assigned one already), try to find the menu name
          // of the parent item in the currently stored menu links.
          if (!isset($parent['menu_name'])) {
            $menu_name = db_query("SELECT menu_name FROM {menu_links} WHERE router_path = :router_path AND module = 'system'", array(':router_path' => $parent_path))->fetchField();
            if ($menu_name) {
              $parent['menu_name'] = $menu_name;
            }
          }
          // If the parent item defines a menu name, inherit it.
          if (!empty($parent['menu_name'])) {
            $item['menu_name'] = $parent['menu_name'];
          }
        }
        if (!isset($item['tab_parent'])) {
          // Parent stores the parent of the path.
          $item['tab_parent'] = $parent_path;
        }
        if (!isset($item['tab_root']) && !$parent['_tab']) {
          $item['tab_root'] = $parent_path;
        }
        // If an access callback is not found for a default local task we use
        // the callback from the parent, since we expect them to be identical.
        // In all other cases, the access parameters must be specified.
        if (($item['type'] == MENU_DEFAULT_LOCAL_TASK) && !isset($item['access callback']) && isset($parent['access callback'])) {
          $item['access callback'] = $parent['access callback'];
          if (!isset($item['access arguments']) && isset($parent['access arguments'])) {
            $item['access arguments'] = $parent['access arguments'];
          }
        }
        // Same for page callbacks.
        if (!isset($item['page callback']) && isset($parent['page callback'])) {
          $item['page callback'] = $parent['page callback'];
          if (!isset($item['page arguments']) && isset($parent['page arguments'])) {
            $item['page arguments'] = $parent['page arguments'];
          }
          if (!isset($item['file path']) && isset($parent['file path'])) {
            $item['file path'] = $parent['file path'];
          }
          if (!isset($item['file']) && isset($parent['file'])) {
            $item['file'] = $parent['file'];
            if (empty($item['file path']) && isset($item['module']) && isset($parent['module']) && $item['module'] != $parent['module']) {
              $item['file path'] = drupal_get_path('module', $parent['module']);
            }
          }
        }
        // Same for load arguments: if a loader doesn't have any explict
        // arguments, try to find arguments in the parent.
        if (!isset($item['load arguments'])) {
          foreach ($item['_load_functions'] as $k => $function) {
            // This loader doesn't have any explict arguments...
            if (!is_array($function)) {
              // ... check the parent for a loader at the same position
              // using the same function name and defining arguments...
              if (isset($parent['_load_functions'][$k]) && is_array($parent['_load_functions'][$k]) && key($parent['_load_functions'][$k]) === $function) {
                // ... and inherit the arguments on the child.
                $item['_load_functions'][$k] = $parent['_load_functions'][$k];
              }
            }
          }
        }
      }
    }
    if (!isset($item['access callback']) && isset($item['access arguments'])) {
      // Default callback.
      $item['access callback'] = 'user_access';
    }
    if (!isset($item['access callback']) || empty($item['page callback'])) {
      $item['access callback'] = 0;
    }
    if (is_bool($item['access callback'])) {
      $item['access callback'] = intval($item['access callback']);
    }

    $item['load_functions'] = empty($item['_load_functions']) ? '' : serialize($item['_load_functions']);
    $item += array(
      'access arguments' => array(),
      'access callback' => '',
      'page arguments' => array(),
      'page callback' => '',
      'title arguments' => array(),
      'title callback' => 't',
      'description' => '',
      'description arguments' => array(),
      'description callback' => 't',
      'position' => '',
      'context' => 0,
      'tab_parent' => '',
      'tab_root' => $path,
      'path' => $path,
      'file' => '',
      'file path' => '',
      'include file' => '',
      'route_name' => '',
    );

    // Calculate out the file to be included for each callback, if any.
    if ($item['file']) {
      $file_path = $item['file path'] ? $item['file path'] : drupal_get_path('module', $item['module']);
      $item['include file'] = $file_path . '/' . $item['file'];
    }
  }

  // Sort the masks so they are in order of descending fit.
  $masks = array_keys($masks);
  rsort($masks);

  if ($save) {
    $path_roots = array_values($path_roots);
    // Update the path roots variable and reset the path alias whitelist cache
    // if the list has changed.
    if ($path_roots != \Drupal::state()->get('menu_path_roots')) {
      \Drupal::state()->set('menu_path_roots', array_values($path_roots));
      \Drupal::service('path.alias_manager')->cacheClear();
    }
    _menu_router_save($menu, $masks);
  }

  return array($menu, $masks);
}

/**
 * Saves data from menu_router_build() to the router table.
 */
function _menu_router_save($menu, $masks) {
  // Delete the existing router since we have some data to replace it.
  db_truncate('menu_router')->execute();

  // Prepare insert object.
  $insert = db_insert('menu_router')
    ->fields(array(
      'path',
      'load_functions',
      'to_arg_functions',
      'access_callback',
      'access_arguments',
      'page_callback',
      'page_arguments',
      'fit',
      'number_parts',
      'context',
      'tab_parent',
      'tab_root',
      'title',
      'title_callback',
      'title_arguments',
      'type',
      'description',
      'description_callback',
      'description_arguments',
      'position',
      'weight',
      'include_file',
      'route_name',
    ));

  $num_records = 0;

  foreach ($menu as $item) {
    // Fill in insert object values.
    $insert->values(array(
      'path' => $item['path'],
      'load_functions' => $item['load_functions'],
      'to_arg_functions' => $item['to_arg_functions'],
      'access_callback' => $item['access callback'],
      'access_arguments' => serialize($item['access arguments']),
      'page_callback' => $item['page callback'],
      'page_arguments' => serialize($item['page arguments']),
      'fit' => $item['_fit'],
      'number_parts' => $item['_number_parts'],
      'context' => $item['context'],
      'tab_parent' => $item['tab_parent'],
      'tab_root' => $item['tab_root'],
      'title' => $item['title'],
      'title_callback' => $item['title callback'],
      'title_arguments' => ($item['title arguments'] ? serialize($item['title arguments']) : ''),
      'type' => $item['type'],
      'description' => $item['description'],
      'description_callback' => $item['description callback'],
      'description_arguments' => ($item['description arguments'] ? serialize($item['description arguments']) : ''),
      'position' => $item['position'],
      'weight' => $item['weight'],
      'include_file' => $item['include file'],
      'route_name' => $item['route_name'],
    ));

    // Execute in batches to avoid the memory overhead of all of those records
    // in the query object.
    if (++$num_records == 20) {
      $insert->execute();
      $num_records = 0;
    }
  }
  // Insert any remaining records.
  $insert->execute();
  // Store the masks.
  \Drupal::state()->set('menu.masks', $masks);

  return $menu;
}

/**
 * Checks whether the site is in maintenance mode.
 *
 * This function will log the current user out and redirect to front page
 * if the current user has no 'access site in maintenance mode' permission.
 *
 * @param $check_only
 *   If this is set to TRUE, the function will perform the access checks and
 *   return the site offline status, but not log the user out or display any
 *   messages.
 *
 * @return
 *   FALSE if the site is not in maintenance mode, the user login page is
 *   displayed, or the user has the 'access site in maintenance mode'
 *   permission. TRUE for anonymous users not being on the login page when the
 *   site is in maintenance mode.
 */
function _menu_site_is_offline($check_only = FALSE) {
  // Check if site is in maintenance mode.
  if (\Drupal::state()->get('system.maintenance_mode')) {
    if (user_access('access site in maintenance mode')) {
      // Ensure that the maintenance mode message is displayed only once
      // (allowing for page redirects) and specifically suppress its display on
      // the maintenance mode settings page.
      if (!$check_only && current_path() != 'admin/config/development/maintenance') {
        if (user_access('administer site configuration')) {
          drupal_set_message(t('Operating in maintenance mode. <a href="@url">Go online.</a>', array('@url' => url('admin/config/development/maintenance'))), 'status', FALSE);
        }
        else {
          drupal_set_message(t('Operating in maintenance mode.'), 'status', FALSE);
        }
      }
    }
    else {
      return TRUE;
    }
  }
  return FALSE;
}

/**
 * @} End of "defgroup menu".
 */