<?php
function template_preprocess_html(&$variables) {
  $variables['page'] = $variables['html']['page'];
  unset($variables['html']['page']);
  $variables['page_top'] = NULL;
  if (isset($variables['html']['page_top'])) {
    $variables['page_top'] = $variables['html']['page_top'];
    unset($variables['html']['page_top']);
  }
  $variables['page_bottom'] = NULL;
  if (isset($variables['html']['page_bottom'])) {
    $variables['page_bottom'] = $variables['html']['page_bottom'];
    unset($variables['html']['page_bottom']);
  }

  $variables['html_attributes'] = new Attribute();

  // HTML element attributes.
  $language_interface = \Drupal::languageManager()->getCurrentLanguage();
  $variables['html_attributes']['lang'] = $language_interface->getId();
  $variables['html_attributes']['dir'] = $language_interface->getDirection();

  if (isset($variables['db_is_active']) && !$variables['db_is_active']) {
    $variables['db_offline'] = TRUE;
  }

  // Add a variable for the root path. This can be used to create a class and
  // theme the page depending on the current path (e.g. node, admin, user) as
  // well as more specific data like path-frontpage.
  $is_front_page =  \Drupal::service('path.matcher')->isFrontPage();

  if ($is_front_page) {
    $variables['root_path'] = FALSE;
  }
  else {
    $system_path = \Drupal::service('path.current')->getPath();
    $variables['root_path'] = explode('/', $system_path)[1];
  }

  $site_config = \Drupal::config('system.site');
  // Construct page title.
  if (!empty($variables['page']['#title'])) {
    $head_title = array(
      'title' => trim(strip_tags($variables['page']['#title'])),
      'name' => $site_config->get('name'),
    );
  }
  // @todo Remove once views is not bypassing the view subscriber anymore.
  //   @see https://www.drupal.org/node/2068471
  elseif ($is_front_page) {
    $head_title = array(
      'title' => t('Home'),
      'name' => $site_config->get('name'),
    );
  }
  else {
    $head_title = ['name' => $site_config->get('name')];
    if ($site_config->get('slogan')) {
      $head_title['slogan'] = strip_tags($site_config->get('slogan'));
    }
  }

  $variables['head_title'] = $head_title;
  // @deprecated in Drupal 8.0.0, will be removed before Drupal 9.0.0.
  $variables['head_title_array'] = $head_title;

  // Collect all attachments. This must happen in the preprocess function for
  // #type => html, to ensure that attachments added in #pre_render callbacks
  // for #type => html are included.
  $attached = $variables['html']['#attached'];
  $attached = drupal_merge_attached($attached, $variables['page']['#attached']);
  if (isset($variables['page_top'])) {
    $attached = drupal_merge_attached($attached, $variables['page_top']['#attached']);
  }
  if (isset($variables['page_bottom'])) {
    $attached = drupal_merge_attached($attached, $variables['page_bottom']['#attached']);
  }

  // Render the attachments into HTML markup to be used directly in the template
  // for #type => html: html.html.twig.
  $all_attached = ['#attached' => $attached];
  $assets = AttachedAssets::createFromRenderArray($all_attached);
  // Take Ajax page state into account, to allow for something like Turbolinks
  // to be implemented without altering core.
  // @see https://github.com/rails/turbolinks/
  $ajax_page_state = \Drupal::request()->request->get('ajax_page_state');
  $assets->setAlreadyLoadedLibraries(isset($ajax_page_state) ? explode(',', $ajax_page_state['libraries']) : []);
  // Optimize CSS/JS if necessary, but only during normal site operation.
  $optimize_css = !defined('MAINTENANCE_MODE') && \Drupal::config('system.performance')->get('css.preprocess');
  $optimize_js = !defined('MAINTENANCE_MODE') && \Drupal::config('system.performance')->get('js.preprocess');
  // Render the asset collections.
  $asset_resolver = \Drupal::service('asset.resolver');
  $variables['styles'] = \Drupal::service('asset.css.collection_renderer')->render($asset_resolver->getCssAssets($assets, $optimize_css));
  list($js_assets_header, $js_assets_footer) = $asset_resolver->getJsAssets($assets, $optimize_js);
  $js_collection_renderer = \Drupal::service('asset.js.collection_renderer');
  $variables['scripts'] = $js_collection_renderer->render($js_assets_header);
  $variables['scripts_bottom'] = $js_collection_renderer->render($js_assets_footer);
  // Also create the alternative version of the aggregate that is unoptimized,
  // but annotated with deep links to the license information on the
  // JavaScript License Web Labels page.
  // @see \Drupal\system\Controller\AssetLicenseInfoController
  \Drupal::service('asset.js.collection_optimizer_license_web_labels_annotator')->optimize($js_assets_header);
  \Drupal::service('asset.js.collection_optimizer_license_web_labels_annotator')->optimize($js_assets_footer);

  // Handle all non-asset attachments.
  drupal_process_attached($all_attached);
  $variables['head'] = drupal_get_html_head(FALSE);
}