<?php

/**
 * @file
 * Module to allow Views to be attached as menu items.
 *
 * This module is a utility module and allows an admin to select a view for a menu item instead of a title and link. When
 * the link is rendered, the view is inserted instead of the link. In addition, if the
 * parent item of the menu is a node page, the node id can be passed to the view as an argument using tokens.
 *
 * Original concept by Randall Knutson - LevelTen Interactive.
 * Written and maintained by Mark Carver - LevelTen Interactive.
 * http://www.leveltendesign.com
 */

// Include admin form alter hooks.
module_load_include('inc', 'menu_views', 'menu_views.admin');
//include_once('menu_views.admin.inc');

/**
 * Implements hook_menu().
 */
function menu_views_menu() {
  // Fake callback, needed for menu item add/edit validation.
  $items['<view>'] = array(
    'page callback' => 'drupal_not_found',
    'access callback' => TRUE,
    'type' => MENU_CALLBACK,
  );
  return $items;
}


/**
 * Implements hook_theme_registry_alter().
 * Intercepts theme_menu_link().
 */
function menu_views_theme_registry_alter(&$registry) {
  // Save previous value from registry in case another module/theme overwrites theme_menu_link() as well.
  $registry['menu_views_menu_link_default'] = $registry['menu_link'];
  $registry['menu_link']['function'] = 'menu_views_menu_link';
  // Provide Superfish support.
  if (isset($registry['superfish_menu_item_link'])) {
    $registry['menu_views_superfish_menu_item_link_default'] = $registry['superfish_menu_item_link'];
    $registry['superfish_menu_item_link']['function'] = 'menu_views_superfish_menu_item_link';
  }
  // Provide Responsive Dropdown Menus support.
  if (isset($registry['responsive_dropdown_menus_item_link'])) {
    $registry['menu_views_responsive_dropdown_menus_item_link_default'] = $registry['responsive_dropdown_menus_item_link'];
    $registry['responsive_dropdown_menus_item_link']['function'] = 'menu_views_responsive_dropdown_menus_item_link';
  }
}

/**
 * Implements theme_menu_link().
 * Overrides default theming function to intercept views.
 */
function menu_views_menu_link(array $variables) {
  // Only intercept if this menu link is a view.
  $view = _menu_views_replace_menu_item($variables['element']);
  if ($view !== FALSE) {
    if (!empty($view)) {
      $sub_menu = '';
      $classes = isset($variables['element']['#attributes']['class']) ? $variables['element']['#attributes']['class'] : array();
      $item = _menu_views_get_item($variables['element']);
      foreach (explode(' ', $item['view']['settings']['wrapper_classes']) as $class) {
        if (!in_array($class, $classes)) {
          $classes[] = $class;
        }
      }
      $variables['element']['#attributes']['class'] = $classes;
      if ($variables['element']['#below']) {
        $sub_menu = \Drupal::service("renderer")->render($variables['element']['#below']);
      }
      return '<li' . drupal_attributes($variables['element']['#attributes']) . '>' . $view . $sub_menu . "</li>\n";
    }
    return '';
  }
  // Otherwise, use the default theming function.
  // @FIXME
// theme() has been renamed to _theme() and should NEVER be called directly.
// Calling _theme() directly can alter the expected output and potentially
// introduce security issues (see https://www.drupal.org/node/2195739). You
// should use renderable arrays instead.
// 
// 
// @see https://www.drupal.org/node/2195739
// return theme('menu_views_menu_link_default', $variables);

}

/**
 * Implements theme_superfish_menu_item_link().
 * Overrides default theming function to intercept views.
 */
function menu_views_superfish_menu_item_link(array $variables) {
  // Only intercept if this menu item link is a view.
  if (isset($variables['menu_item']['link']) && $view = _menu_views_replace_menu_item($variables['menu_item']['link'])) {
    $item = _menu_views_get_item($variables['menu_item']['link']);
    return '<div' . drupal_attributes(array('class' => explode(' ', $item['view']['settings']['wrapper_classes']))) . '>' . $view . '</div>';
  }
  // Otherwise, use the default theming function.
  // @FIXME
// theme() has been renamed to _theme() and should NEVER be called directly.
// Calling _theme() directly can alter the expected output and potentially
// introduce security issues (see https://www.drupal.org/node/2195739). You
// should use renderable arrays instead.
// 
// 
// @see https://www.drupal.org/node/2195739
// return theme('menu_views_superfish_menu_item_link_default', $variables);

}

/**
 * Implements theme_responsive_dropdown_menus_item_link().
 * Overrides default theming function to intercept views.
 */
function menu_views_responsive_dropdown_menus_item_link(array $variables) {
  // Only intercept if this menu item link is a view.
  if (isset($variables['menu_item']['link']) && $view = _menu_views_replace_menu_item($variables['menu_item']['link'])) {
    $item = _menu_views_get_item($variables['menu_item']['link']);
    return '<div' . drupal_attributes(array('class' => explode(' ', $item['view']['settings']['wrapper_classes']))) . '>' . $view . '</div>';
  }
  // Otherwise, use the default theming function.
  // @FIXME
// theme() has been renamed to _theme() and should NEVER be called directly.
// Calling _theme() directly can alter the expected output and potentially
// introduce security issues (see https://www.drupal.org/node/2195739). You
// should use renderable arrays instead.
// 
// 
// @see https://www.drupal.org/node/2195739
// return theme('menu_views_responsive_dropdown_menus_item_link_default', $variables);

}

/**
 * Implements hook_menu_breadcrumb_alter().
 */
function menu_views_menu_breadcrumb_alter(&$active_trail, $item) {
  foreach ($active_trail as $key => $parent) {
    if (isset($parent['link_path']) && $parent['link_path'] == '<view>') {
      $menu_view = _menu_views_get_item($parent);
      _menu_views_tokenize($menu_view);
      // Remove this breadcrumb if the menu item view wants it hidden.
      if (!(bool)$menu_view['view']['settings']['breadcrumb']) {
        unset($active_trail[$key]);
      }
      else {
        // Use overridden title if provided.
        $title = \Drupal\Component\Utility\Xss::filterAdmin($menu_view['view']['settings']['breadcrumb_title']);
        // Use title provided by view next.
        if (empty($title)) {
          $view = views_get_view($menu_view['view']['name']);
          if ($view && $view->access($menu_view['view']['display']) && $view->set_display($menu_view['view']['display'])) {
            $title = \Drupal\Component\Utility\Xss::filterAdmin($view->get_title());
            $view->destroy();
          }
        }
        // If title is still empty, just remove it from the breadcrumb.
        if (empty($title)) {
          unset($active_trail[$key]);
        }
        else {
          $active_trail[$key]['title'] = $title;
          $active_trail[$key]['href'] = $menu_view['view']['settings']['breadcrumb_path'];
        }
      }
    }
  }
}

function _menu_views_replace_menu_item($element) {
  $build = array();
  $item = _menu_views_get_item($element);
  _menu_views_tokenize($item);
  if ($item['type'] == 'view' && $item['view']['name'] && $item['view']['display']) {
    $element['#attributes']['class'][] = 'menu-views';
    if ($view = views_get_view($item['view']['name'])) {
      if ($view->access($item['view']['display']) && $view->set_display($item['view']['display'])) {
        $arguments = explode('/', $item['view']['arguments']);
        // Need to replace empty arguments with NULL values for views.
        foreach ($arguments as $key => $value) {
          if (empty($value)) {
            $arguments[$key] = NULL;
          }
        }
        $view->set_arguments($arguments);
        $build['view'] = array(
          '#markup' => $view->preview(),
          '#weight' => 10,
        );

        // Provide title options for the view.
        if ((bool)$item['view']['settings']['title']) {
          $title = \Drupal\Component\Utility\Xss::filterAdmin($item['view']['settings']['title_override']);
          if (empty($title)) {
            $title = \Drupal\Component\Utility\Xss::filterAdmin($view->get_title());
          }
          if (!empty($title)) {
            $tag = $item['view']['settings']['title_wrapper'];
            if ($tag === '0') {
              $tag = FALSE;
            }
            elseif ($tag === '') {
              $tag = 'h3';
            }
            if ($tag) {
              $title_attributes = array();
              if (!empty($item['view']['settings']['title_classes'])) {
                $title_attributes['class'] = array_filter(explode(' ', $item['view']['settings']['title_classes']));
                foreach ($title_attributes['class'] as $key => $class) {
                  $title_attributes['class'][$key] = \Drupal\Component\Utility\Html::getClass($class);
                }
              }
              $build['title'] = array(
                '#theme' => 'html_tag__menu_views__title',
                '#tag' => $tag,
                '#attributes' => $title_attributes,
                '#value' => \Drupal\Component\Utility\Xss::filterAdmin($title),
              );
            }
            else {
              $build['title'] = array(
                '#markup' => $title,
              );
            }
          }
        }

        // Add contextual links if allowed and if views_ui module is enabled.
        if (\Drupal::moduleHandler()->moduleExists('contextual_links') && \Drupal::currentUser()->hasPermission('access contextual links') && \Drupal::moduleHandler()->moduleExists('views_ui')) {
          views_add_contextual_links($build, 'special_block_-exp', $view, $item['view']['display']);
          if (!empty($build['#contextual_links'])) {
            $build['#prefix'] = '<div class="contextual-links-region">';
            $build['#suffix'] = '</div>';
            $build['contextual_links'] = array(
              '#type' => 'contextual_links',
              '#contextual_links' => $build['#contextual_links'],
              '#element' => $build,
              '#weight' => -1,
            );
          }
        }

        $view->destroy();
      }
    }
    return \Drupal::service("renderer")->render($build);
  }
  return FALSE;
}

function _menu_views_default_values() {
  return array(
    'mlid' => 0,
    'type' => 'link',
    'original_path' => '',
    'view' => array(
      'name' => FALSE,
      'display' => FALSE,
      'arguments' => '',
      'settings' => array(
        'wrapper_classes' => 'menu-views',
        'breadcrumb' => TRUE,
        'breadcrumb_title' => '',
        'breadcrumb_path' => '<front>',
        'title' => FALSE,
        'title_wrapper' => '',
        'title_classes' => '',
        'title_override' => '',
      ),
    ),
  );
}

/**
 * Helper function to determine whether the form menu item options are a tree.
 */
function _menu_views_options_tree($form) {
  return ((isset($form['#node']) && isset($form['menu']['link']['options']['#tree']) && $form['menu']['link']['options']['#tree']) || (isset($form['options']['#tree']) && $form['options']['#tree']));
}

/**
 * Helper function to return the menu view array from a menu item array or form array.
 */
function _menu_views_get_item(array &$element = array(), array &$form_state = array()) {
  // Default values.
  $item = $default = _menu_views_default_values();
  // Remove the type of menu item, will get set afterwards.
  unset($item['type']);
  $provided = FALSE;
  $ajax_type = FALSE;
  // If $form_state is empty, this is a menu item.
  if (empty($form_state)) {
    if (isset($element['menu_views'])) {
      $provided = &$element['menu_views'];
    }
    elseif (isset($element['localized_options']['menu_views'])) {
      $provided = &$element['localized_options']['menu_views'];
    }
    elseif (isset($element['#localized_options']['menu_views'])) {
      $provided = &$element['#localized_options']['menu_views'];
    }
    elseif (isset($element['options']['menu_views'])) {
      $provided = &$element['options']['menu_views'];
    }
  }
  // $form_state should be set when used in forms, otherwise this function will not work.
  else {
    $original_element = $element;
    $values = &$form_state['values'];
    // Determine if this is a node form.
    if (isset($element['#node'])) {
      $element = &$element['menu']['link'];
      $values = &$values['menu'];
    }
    // Save the menu item type before proceeding.
    if (isset($values['menu_item_type'])) {
      $ajax_type = $values['menu_item_type'];
    }
    elseif (isset($values['menu']['menu_views']['menu_item_type'])) {
      $ajax_type = $values['menu']['menu_views']['menu_item_type'];
    }
    // Save the menu item provided for initial form population.
    if (isset($element['original_item']['#value']['options']['menu_views'])) {
      $provided = &$element['original_item']['#value']['options']['menu_views'];
      if (isset($provided['type'])) {
        $item['type'] = $provided['type'];
      }
    }
    elseif (isset($original_element['#node']->menu['options']['menu_views'])) {
      $provided = &$original_element['#node']->menu['options']['menu_views'];
      if (isset($provided['type'])) {
        $item['type'] = $provided['type'];
      }
    }
    // Determine if the options has a tree value.
    if (_menu_views_options_tree($original_element)) {
      $element = &$element['options'];
      $values = &$values['options'];
    }
    if (!$provided && isset($element['menu_views'])) {
      if (isset($element['menu_views']['#value'])) {
        $provided = $element['menu_views']['#value'];
      }
      elseif (isset($element['menu_views'])) {
        $provided = $element['menu_views'];
      }
    }
    // Allow submitted values to override form values.
    if (isset($values['menu_views'])) {
      $provided = $values['menu_views'];
    }
    if (isset($provided['type']) && isset($item['type'])) {
      $provided['type'] = $item['type'];
    }
  }
  // If the menu view element were not set, attempt to determine if this is a form.
  // By default, the menu view returns default values (no view). If settings were provided by an element or form item, then use those.
  if ($provided) {
    // Extract available element settings to use for this menu view.
    foreach (array('mlid', 'original_path', 'view') as $property) {
      if (isset($provided[$property])) {
        if (isset($item[$property]) && is_array($item[$property])) {
          $item[$property] = _menu_views_array_merge_recursive($item[$property], $provided[$property]);
        }
        else {
          $item[$property] = $provided[$property];
        }
      }
    }
  }
  // Set the type of menu item.
  if ($ajax_type) {
    $item['type'] = $ajax_type;
  }
  elseif (isset($provided['type'])) {
    $item['type'] = $provided['type'];
  }
  else {
    $item['type'] = $default['type'];
  }
  // Filter out any disabled views.
  $views = array_keys(views_get_enabled_views());
  if (!in_array($item['view']['name'], $views)) {
    $item['view'] = $default['view'];
  }
  return $item;
}

function menu_views_menu_link_alter(&$link) {
  $item = _menu_views_get_item($link);
  if ($item['type'] == 'view') {
    if (isset($link['link_path']) && $link['link_path'] != '<view>') {
      $item['original_path'] = $link['link_path'];
    }
    $link['link_path'] = '<view>';
  }
}

/**
 * Helper function to return the menu link item based on it's original path.
 *
 * @param (string) $original_path
 *   The [node] path for which to search for in menu views.
 * @param (string)|(array) $menu_name
 *   Limit the search of menu view items to the specified menu names.
 * @return
 *   (array) $mlids
 *   A keyed array containing the identification integers matching the original path of menu items in the {menu_links} table,
 *   or an empty array if no menu items were found.
 *
 * @see: menu_views_node_prepare() and menu_views_node_delete().
 */
function _menu_views_items_from_original_path($original_path, $menu_name = NULL) {
  $mlids = array();
  // Build the query.
  $query = db_select('menu_links', 'm')
            ->fields('m', array('mlid', 'options'))
            ->condition('module', 'menu')
            ->condition('link_path', '<view>');
  // Set the menu_name condition if present.
  if (!empty($menu_name)) {
    $query = $query->condition('menu_name', $menu_name);
  }
  // Execute the query.
  $query = $query->execute();
  // Iterate through all available menu items that are views to match against the original path.
  while($link = $query->fetchObject()) {
    if (PHP_VERSION_ID >= 70000) {
      // FIXME $options = unserialize($link->options, array('allowed_classes' => ['Class1', 'Class2']));
      $options = unserialize($link->options);
    } else {
      $options = unserialize($link->options);
    }

    if ($options) {
      $item = _menu_views_get_item($options);
      if ($item['original_path'] == $original_path) {
        $mlids[] = $link->mlid;
        break;
      }
    }
  }
  return $mlids;
}


/**
 * Implements hook_node_prepare().
 */
function menu_views_node_prepare($node) {
  // Manually call menu's hook_node_prepare() if $node->menu doesn't exist.
  // @see: drupal.org/node/1878968
  if (!isset($node->menu) || empty($node->menu)) {
    menu_node_prepare($node);
  }
  if (isset($node->nid) && !$node->menu['mlid']) {
    // Prepare the node for the edit form so that $node->menu always exists.
    // @FIXME
// // @FIXME
// // The correct configuration object could not be determined. You'll need to
// // rewrite this call manually.
// $menu_name = strtok(variable_get('menu_parent_' . $node->type, 'main-menu:0'), ':');

    $item = array();
    $mlids = array();
    // Give priority to the default menu.
    // @FIXME
// // @FIXME
// // The correct configuration object could not be determined. You'll need to
// // rewrite this call manually.
// $type_menus = variable_get('menu_options_' . $node->type, array('main-menu' => 'main-menu'));

    if (in_array($menu_name, $type_menus)) {
      $mlids = _menu_views_items_from_original_path('node/' . $node->nid, $menu_name);
    }
    // Check all allowed menus if a link does not exist in the default menu.
    if (empty($mlid) && !empty($type_menus)) {
      $mlids = _menu_views_items_from_original_path('node/' . $node->nid, array_values($type_menus));
    }
    // Load the menu link if one was found.
    $item = empty($mlids) ? array() : menu_link_load(reset($mlids));
    // Set default values.
    $default = array(
      'link_title' => '',
      'mlid' => 0,
      'plid' => 0,
      'menu_name' => $menu_name,
      'weight' => 0,
      'options' => array(),
      'module' => 'menu',
      'expanded' => 0,
      'hidden' => 0,
      'has_children' => 0,
      'customized' => 0,
    );
    // Set the menu item.
    $node->menu = _menu_views_array_merge_recursive($default, $item);
    // Find the depth limit for the parent select.
    if (!isset($node->menu['parent_depth_limit'])) {
      $node->menu['parent_depth_limit'] = _menu_parent_depth_limit($node->menu);
    }
  }
}

/**
 * Implements hook_node_delete().
 */
function menu_views_node_delete(\Drupal\node\NodeInterface $node) {
  $mlids = _menu_views_items_from_original_path('node/' . $node->id());
  foreach ($mlids as $mlid) {
    menu_link_delete($mlid);
  }
}

/**
 * Implements hook_node_insert().
 */
function menu_views_node_insert(\Drupal\node\NodeInterface $node) {
  menu_views_node_save($node);
}

/**
 * Implements hook_node_presave().
 */
function menu_views_node_presave(\Drupal\node\NodeInterface $node) {
  if (isset($node->menu)) {
    $link = &$node->menu;
    $item = _menu_views_get_item($link);
    // Ensure the enabled property is set.
    if (!isset($link['enabled'])) {
      $link['enabled'] = !(bool) $link['hidden'];
    }
    // If this is a menu view item, override properties on the link so this module handles the save.
    if ($link['enabled'] && $item['type'] == 'view') {
      // Save the mlid in the menu_views array so the menu module doesn't delete the link when it detects the mlid.
      if (!empty($link['mlid'])) {
        $link['options']['menu_views']['mlid'] = $link['mlid'];
        $link['mlid'] = 0;
      }
      // Ensure there is no title so the menu module doesn't try to save this menu item.
      $link['link_title'] = '';
    }
  }
}


/**
 * Implements hook_node_update().
 */
function menu_views_node_update(\Drupal\node\NodeInterface $node) {
  menu_views_node_save($node);
}


/**
 * Helper for hook_node_insert() and hook_node_update().
 */
function menu_views_node_save(\Drupal\node\NodeInterface $node) {
  if (isset($node->menu)) {
    $link = &$node->menu;
    $item = _menu_views_get_item($link);
    // Check to see if Menu Views should handle the menu item save.
    if (!empty($link['enabled']) && $item['type'] == 'view') {
      // If this an existing menu item, check to see if the mlid was saved in the menu view options array.
      if (!empty($item['mlid']) && empty($link['mlid'])) {
        $link['mlid'] = $item['mlid'];
      }
      // This is a new menu link, create one so we can get the mlid.
      // Note: This will save the menu link twice on new nodes, which is unavoidable since
      // we need the mlid to be saved in the menu views options array.
      elseif (empty($link['mlid'])) {
        if (!menu_link_save($link)) {
          drupal_set_message(t('There was an error saving the menu link.'), 'error');
          return;
        }
      }
      // Ensure mlid is properly set.
      $item['mlid'] = $link['mlid'];
      // Ensure link_path is properly set.
      $link['link_path'] = '<view>';
      // Ensure original_path is properly set.
      $item['original_path'] = 'node/' . $node->id();
      // Replace the menu view options in the link and save it.
      $link['options']['menu_views'] = $item;
      if (!menu_link_save($link)) {
        drupal_set_message(t('There was an error saving the menu link.'), 'error');
      }
    }
  }
}


/**
 * Implements hook_token_info().
 */
function menu_views_token_info() {
  $tokens['tokens']['menu-link']['node'] = array(
    'name' => t('Node'),
    'description' => t('The node of the menu link.'),
    'type' => 'node',
  );
  $tokens['tokens']['menu-link']['parent']['node'] = array(
    'name' => t('Node'),
    'description' => t('The node of the menu link\'s parent.'),
    'type' => 'node',
  );
  return $tokens;
}


/**
 * Implements hook_tokens().
 */
function menu_views_tokens($type, $tokens, array $data = array(), array $options = array()) {
  $url_options = array('absolute' => TRUE);
  if (isset($options['language'])) {
    $url_options['language'] = $options['language'];
    $language_code = $options['language']->language;
  }
  else {
    $language_code = NULL;
  }
  $sanitize = !empty($options['sanitize']);
  $replacements = array();
  // Menu link tokens.
  if ($type == 'menu-link' && !empty($data['menu-link'])) {
    $link = (array) $data['menu-link'];
    // menu-link:node tokens.
    if ($node_tokens = \Drupal::token()->findWithPrefix($tokens, 'node')) {
      $node = \Drupal::routeMatch()->getParameter('node', 1, $link['link_path']);
      if (!$node && '<view>' === $link['link_path'] && !empty($link['options']['menu_views']['original_path'])) {
        $node = \Drupal::routeMatch()->getParameter('node', 1, $link['options']['menu_views']['original_path']);
      }
      if ($node) {
        $replacements += \Drupal::token()->generate('node', $node_tokens, array('node' => $node), $options);
      }
      else {
        $replacements += \Drupal::token()->generate('node', $node_tokens, array('node' => NULL), $options);
      }
    }
    // menu-link:parent tokens.
    elseif (($parent_tokens = \Drupal::token()->findWithPrefix($tokens, 'parent')) && !empty($link['plid']) && ($parent = menu_link_load($link['plid']))) {
      $node = \Drupal::routeMatch()->getParameter('node', 1, $parent['link_path']);
      if (!$node && '<view>' === $parent['link_path'] && !empty($parent['options']['menu_views']['original_path'])) {
        $node = \Drupal::routeMatch()->getParameter('node', 1, $parent['options']['menu_views']['original_path']);
      }
      if ($node) {
        $replacements += \Drupal::token()->generate('node', $parent_tokens, array('node' => $node), $options);
      }
      else {
        $replacements += \Drupal::token()->generate('node', $parent_tokens, array('node' => NULL), $options);
      }
    }
  }
  return $replacements;
}


/**
 * Helper function to tokenize a menu item view arguments and settings.
 * Alters the menu view item array and the original values are replaced.
 */
function _menu_views_tokenize(&$item) {
  if (isset($item['mlid']) && $item['mlid'] > 0) {
    $context['menu-link'] = menu_link_load($item['mlid']);
    $options = array(
      'callback' => '_menu_views_tokenize_callback',
    );
    if (isset($item['view']['arguments']) && !empty($item['view']['arguments'])) {
      $item['view']['arguments'] = \Drupal::token()->replace($item['view']['arguments'], $context, array_merge($options, array('urlencode' => TRUE, 'clear' => TRUE)));
    }
    $tokenizable_settings = array('breadcrumb_title', 'breadcrumb_path', 'title_override');
    if (isset($item['view']['settings'])) {
      foreach ($item['view']['settings'] as $key => $value) {
        if (in_array($key, $tokenizable_settings)) {
          $item['view']['settings'][$key] = \Drupal::token()->replace($value, $context, $options);
        }
      }
    }
  }
}


/**
 * Callback for human-readable token value replacements.
 */
function _menu_views_tokenize_callback(&$replacements, $data, $options) {
  foreach ($replacements as $token => $value) {
    if (isset($options['urlencode']) && $options['urlencode']) {
      $replacements[$token] = urlencode($value);
    }
  }
}


/**
 * array_merge_recursive does indeed merge arrays, but it converts values with duplicate
 * keys to arrays rather than overwriting the value in the first array with the duplicate
 * value in the second array, as array_merge does. I.e., with array_merge_recursive,
 * this happens (documented behavior):
 * 
 * array_merge_recursive(array('key' => 'org value'), array('key' => 'new value'));
 *     => array('key' => array('org value', 'new value'));
 * 
 * array_merge_recursive_distinct does not change the datatypes of the values in the arrays.
 * Matching keys' values in the second array overwrite those in the first array, as is the
 * case with array_merge, i.e.:
 * 
 * array_merge_recursive_distinct(array('key' => 'org value'), array('key' => 'new value'));
 *     => array('key' => 'new value');
 * 
 * Parameters are passed by reference, though only for performance reasons. They're not
 * altered by this function.
 * 
 * @param array $array1
 * @param mixed $array2
 * @author daniel@danielsmedegaardbuus.dk
 * @return array
 */
function &_menu_views_array_merge_recursive(array &$array1, &$array2 = NULL) {
  $merged = $array1;
  if (is_array($array2)) {
    foreach ($array2 as $key => $val) {
      if (is_array($array2[$key])) {
        $merged[$key] = isset($merged[$key]) && is_array($merged[$key]) ? _menu_views_array_merge_recursive($merged[$key], $array2[$key]) : $array2[$key];
      }        
      else {
        $merged[$key] = $val;
      }
    }
  }
  return $merged;
}