abstract class CachePluginBase

abstract class CachePluginBase extends PluginBase {

  /**
   * Contains all data that should be written/read from cache.
   */
  var $storage = array();

  /**
   * What table to store data in.
   */
  var $table = 'views_results';

  /**
   * Stores the cache ID used for the results cache.
   *
   * The cache ID is stored in generateResultsKey() got executed.
   *
   * @var string
   *
   * @see Drupal\views\Plugin\views\cache\CachePluginBase::generateResultsKey()
   */
  protected $resultsKey;

  /**
   * Stores the cache ID used for the output cache, once generateOutputKey() got
   * executed.
   *
   * @var string
   *
   * @see Drupal\views\Plugin\views\cache\CachePluginBase::generateOutputKey()
   */
  protected $outputKey;

  /**
   * Initialize the plugin.
   *
   * @param $view
   *   The view object.
   * @param $display
   *   The display handler.
   */
  public function init(ViewExecutable $view, &$display, $options = NULL) {
    $this
      ->setOptionDefaults($this->options, $this
      ->defineOptions());
    $this->view =& $view;
    $this->displayHandler =& $display;
    $this
      ->unpackOptions($this->options, $options);
  }

  /**
   * Returns the outputKey property.
   *
   * @return string
   *   The outputKey property.
   */
  public function getOutputKey() {
    return $this->outputKey;
  }

  /**
   * Returns the resultsKey property.
   *
   * @return string
   *   The resultsKey property.
   */
  public function getResultsKey() {
    return $this->resultsKey;
  }

  /**
   * Return a string to display as the clickable title for the
   * access control.
   */
  public function summaryTitle() {
    return t('Unknown');
  }

  /**
   * Determine the expiration time of the cache type, or NULL if no expire.
   *
   * Plugins must override this to implement expiration.
   *
   * @param $type
   *   The cache type, either 'query', 'result' or 'output'.
   */
  function cache_expire($type) {
  }

  /**
   * Determine expiration time in the cache table of the cache type
   * or CACHE_PERMANENT if item shouldn't be removed automatically from cache.
   *
   * Plugins must override this to implement expiration in the cache table.
   *
   * @param $type
   *   The cache type, either 'query', 'result' or 'output'.
   */
  function cache_set_expire($type) {
    return CacheBackendInterface::CACHE_PERMANENT;
  }

  /**
   * Save data to the cache.
   *
   * A plugin should override this to provide specialized caching behavior.
   */
  function cache_set($type) {
    switch ($type) {
      case 'query':

        // Not supported currently, but this is certainly where we'd put it.
        break;
      case 'results':
        $data = array(
          'result' => $this->view->result,
          'total_rows' => isset($this->view->total_rows) ? $this->view->total_rows : 0,
          'current_page' => $this->view
            ->getCurrentPage(),
        );
        cache($this->table)
          ->set($this
          ->generateResultsKey(), $data, $this
          ->cache_set_expire($type));
        break;
      case 'output':
        $this->storage['output'] = $this->view->display_handler->output;
        $this
          ->gather_headers();
        cache($this->table)
          ->set($this
          ->generateOutputKey(), $this->storage, $this
          ->cache_set_expire($type));
        break;
    }
  }

  /**
   * Retrieve data from the cache.
   *
   * A plugin should override this to provide specialized caching behavior.
   */
  function cache_get($type) {
    $cutoff = $this
      ->cache_expire($type);
    switch ($type) {
      case 'query':

        // Not supported currently, but this is certainly where we'd put it.
        return FALSE;
      case 'results':

        // Values to set: $view->result, $view->total_rows, $view->execute_time,
        // $view->current_page.
        if ($cache = cache($this->table)
          ->get($this
          ->generateResultsKey())) {
          if (!$cutoff || $cache->created > $cutoff) {
            $this->view->result = $cache->data['result'];
            $this->view->total_rows = $cache->data['total_rows'];
            $this->view
              ->setCurrentPage($cache->data['current_page']);
            $this->view->execute_time = 0;
            return TRUE;
          }
        }
        return FALSE;
      case 'output':
        if ($cache = cache($this->table)
          ->get($this
          ->generateOutputKey())) {
          if (!$cutoff || $cache->created > $cutoff) {
            $this->storage = $cache->data;
            $this->view->display_handler->output = $cache->data['output'];
            $this
              ->restore_headers();
            return TRUE;
          }
        }
        return FALSE;
    }
  }

  /**
   * Clear out cached data for a view.
   *
   * We're just going to nuke anything related to the view, regardless of display,
   * to be sure that we catch everything. Maybe that's a bad idea.
   */
  function cache_flush() {
    cache($this->table)
      ->deleteTags(array(
      $this->view->storage
        ->get('name') => TRUE,
    ));
  }

  /**
   * Post process any rendered data.
   *
   * This can be valuable to be able to cache a view and still have some level of
   * dynamic output. In an ideal world, the actual output will include HTML
   * comment based tokens, and then the post process can replace those tokens.
   *
   * Example usage. If it is known that the view is a node view and that the
   * primary field will be a nid, you can do something like this:
   *
   * <!--post-FIELD-NID-->
   *
   * And then in the post render, create an array with the text that should
   * go there:
   *
   * strtr($output, array('<!--post-FIELD-1-->', 'output for FIELD of nid 1');
   *
   * All of the cached result data will be available in $view->result, as well,
   * so all ids used in the query should be discoverable.
   */
  function post_render(&$output) {
  }

  /**
   * Start caching the html head.
   *
   * This takes a snapshot of the current system state so that we don't
   * duplicate it. Later on, when gather_headers() is run, this information
   * will be removed so that we don't hold onto it.
   *
   * @see drupal_add_html_head()
   */
  function cache_start() {
    $this->storage['head'] = drupal_add_html_head();
  }

  /**
   * Gather the JS/CSS from the render array, the html head from the band data.
   */
  function gather_headers() {

    // Simple replacement for head
    if (isset($this->storage['head'])) {
      $this->storage['head'] = str_replace($this->storage['head'], '', drupal_add_html_head());
    }
    else {
      $this->storage['head'] = '';
    }
    $attached = drupal_render_collect_attached($this->storage['output']);
    $this->storage['css'] = $attached['css'];
    $this->storage['js'] = $attached['js'];
  }

  /**
   * Restore out of band data saved to cache. Copied from Panels.
   */
  function restore_headers() {
    if (!empty($this->storage['head'])) {
      drupal_add_html_head($this->storage['head']);
    }
    if (!empty($this->storage['css'])) {
      foreach ($this->storage['css'] as $args) {
        $this->view->element['#attached']['css'][] = $args;
      }
    }
    if (!empty($this->storage['js'])) {
      foreach ($this->storage['js'] as $key => $args) {
        if ($key !== 'settings') {
          $this->view->element['#attached']['js'][] = $args;
        }
        else {
          foreach ($args as $setting) {
            $this->view->element['#attached']['js']['setting'][] = $setting;
          }
        }
      }
    }
  }

  /**
   * Calculates and sets a cache ID used for the result cache.
   *
   * @return string
   *   The generated cache ID.
   */
  public function generateResultsKey() {
    global $user;
    if (!isset($this->resultsKey)) {
      $build_info = $this->view->build_info;
      foreach (array(
        'query',
        'count_query',
      ) as $index) {

        // If the default query back-end is used generate SQL query strings from
        // the query objects.
        if ($build_info[$index] instanceof Select) {
          $query = clone $build_info[$index];
          $query
            ->preExecute();
          $build_info[$index] = (string) $query;
        }
      }
      $key_data = array(
        'build_info' => $build_info,
        'roles' => array_keys($user->roles),
        'super-user' => $user->uid == 1,
        // special caching for super user.
        'langcode' => language(LANGUAGE_TYPE_INTERFACE)->langcode,
        'base_url' => $GLOBALS['base_url'],
      );
      foreach (array(
        'exposed_info',
        'page',
        'sort',
        'order',
        'items_per_page',
        'offset',
      ) as $key) {
        if (isset($_GET[$key])) {
          $key_data[$key] = $_GET[$key];
        }
      }
      $this->resultsKey = $this->view->storage
        ->get('name') . ':' . $this->displayHandler->display['id'] . ':results:' . md5(serialize($key_data));
    }
    return $this->resultsKey;
  }

  /**
   * Calculates and sets a cache ID used for the output cache.
   *
   * @return string
   *   The generated cache ID.
   */
  public function generateOutputKey() {
    global $user;
    if (!isset($this->outputKey)) {
      $key_data = array(
        'result' => $this->view->result,
        'roles' => array_keys($user->roles),
        'super-user' => $user->uid == 1,
        // special caching for super user.
        'theme' => $GLOBALS['theme'],
        'langcode' => language(LANGUAGE_TYPE_INTERFACE)->langcode,
        'base_url' => $GLOBALS['base_url'],
      );
      $this->outputKey = $this->view->storage
        ->get('name') . ':' . $this->displayHandler->display['id'] . ':output:' . md5(serialize($key_data));
    }
    return $this->outputKey;
  }

}