class PerformanceForm

class PerformanceForm extends ConfigFormBase {
  
  /**
   * The date formatter service.
   *
   * @var \Drupal\Core\Datetime\DateFormatterInterface
   */
  protected $dateFormatter;
  
  /**
   * The CSS asset collection optimizer service.
   *
   * @var \Drupal\Core\Asset\AssetCollectionOptimizerInterface
   */
  protected $cssCollectionOptimizer;
  
  /**
   * The JavaScript asset collection optimizer service.
   *
   * @var \Drupal\Core\Asset\AssetCollectionOptimizerInterface
   */
  protected $jsCollectionOptimizer;
  
  /**
   * The module handler.
   *
   * @var \Drupal\Core\Extension\ModuleHandlerInterface
   */
  protected $moduleHandler;
  
  /**
   * Constructs a PerformanceForm object.
   *
   * @param \Drupal\Core\Config\ConfigFactoryInterface $config_factory
   *   The factory for configuration objects.
   * @param \Drupal\Core\Config\TypedConfigManagerInterface $typedConfigManager
   *   The typed config manager.
   * @param \Drupal\Core\Datetime\DateFormatterInterface $date_formatter
   *   The date formatter service.
   * @param \Drupal\Core\Asset\AssetCollectionOptimizerInterface $css_collection_optimizer
   *   The CSS asset collection optimizer service.
   * @param \Drupal\Core\Asset\AssetCollectionOptimizerInterface $js_collection_optimizer
   *   The JavaScript asset collection optimizer service.
   * @param \Drupal\Core\Extension\ModuleHandlerInterface $module_handler
   *   The module handler.
   */
  public function __construct(ConfigFactoryInterface $config_factory, TypedConfigManagerInterface $typedConfigManager, DateFormatterInterface $date_formatter, AssetCollectionOptimizerInterface $css_collection_optimizer, AssetCollectionOptimizerInterface $js_collection_optimizer, ModuleHandlerInterface $module_handler) {
    parent::__construct($config_factory, $typedConfigManager);
    $this->dateFormatter = $date_formatter;
    $this->cssCollectionOptimizer = $css_collection_optimizer;
    $this->jsCollectionOptimizer = $js_collection_optimizer;
    $this->moduleHandler = $module_handler;
  }
  
  /**
   * {@inheritdoc}
   */
  public static function create(ContainerInterface $container) {
    return new static($container->get('config.factory'), $container->get('config.typed'), $container->get('date.formatter'), $container->get('asset.css.collection_optimizer'), $container->get('asset.js.collection_optimizer'), $container->get('module_handler'));
  }
  
  /**
   * {@inheritdoc}
   */
  public function getFormId() {
    return 'system_performance_settings';
  }
  
  /**
   * {@inheritdoc}
   */
  protected function getEditableConfigNames() {
    return [
      'system.performance',
    ];
  }
  
  /**
   * {@inheritdoc}
   */
  public function buildForm(array $form, FormStateInterface $form_state) {
    $form['#attached']['library'][] = 'system/drupal.system';
    $form['caching'] = [
      '#type' => 'details',
      '#title' => $this->t('Caching'),
      '#open' => TRUE,
    ];
    // Identical options to the ones for block caching.
    // @see \Drupal\Core\Block\BlockBase::buildConfigurationForm()
    $period = [
      0,
      60,
      180,
      300,
      600,
      900,
      1800,
      2700,
      3600,
      10800,
      21600,
      32400,
      43200,
      86400,
    ];
    $period = array_map([
      $this->dateFormatter,
      'formatInterval',
    ], array_combine($period, $period));
    $period[0] = '<' . $this->t('no caching') . '>';
    $form['caching']['page_cache_maximum_age'] = [
      '#type' => 'select',
      '#title' => $this->t('Browser and proxy cache maximum age'),
      '#config_target' => 'system.performance:cache.page.max_age',
      '#options' => $period,
      '#description' => $this->t('This is used as the value for max-age in Cache-Control headers.'),
    ];
    $form['caching']['internal_page_cache'] = [
      '#markup' => $this->t('Drupal provides an <a href=":module_enable">Internal Page Cache module</a> that is recommended for small to medium-sized websites.', [
        ':module_enable' => Url::fromRoute('system.modules_list')->toString(),
      ]),
      '#access' => !$this->moduleHandler
        ->moduleExists('page_cache'),
    ];
    $directory = 'assets://';
    $is_writable = is_dir($directory) && is_writable($directory);
    $disabled = !$is_writable;
    $disabled_message = '';
    if (!$is_writable) {
      $disabled_message = ' ' . $this->t('<strong class="error">Set up the <a href=":file-system">optimized assets file system path</a> to make these optimizations available.</strong>', [
        ':file-system' => Url::fromRoute('system.file_system_settings')->toString(),
      ]);
    }
    $form['bandwidth_optimization'] = [
      '#type' => 'details',
      '#title' => $this->t('Bandwidth optimization'),
      '#open' => TRUE,
      '#description' => $this->t('External resources can be optimized automatically, which can reduce both the size and number of requests made to your website.') . $disabled_message,
    ];
    $form['bandwidth_optimization']['preprocess_css'] = [
      '#type' => 'checkbox',
      '#title' => $this->t('Aggregate CSS files'),
      '#config_target' => 'system.performance:css.preprocess',
      '#disabled' => $disabled,
    ];
    $form['bandwidth_optimization']['preprocess_js'] = [
      '#type' => 'checkbox',
      '#title' => $this->t('Aggregate JavaScript files'),
      '#config_target' => 'system.performance:js.preprocess',
      '#disabled' => $disabled,
    ];
    return parent::buildForm($form, $form_state);
  }
  
  /**
   * {@inheritdoc}
   */
  public function submitForm(array &$form, FormStateInterface $form_state) {
    $this->cssCollectionOptimizer
      ->deleteAll();
    $this->jsCollectionOptimizer
      ->deleteAll();
    parent::submitForm($form, $form_state);
  }

}