trait VeflTrait in Views exposed form layout 8.3

trait VeflTrait {

  /**
   * {@inheritdoc}
   */
  protected function defineOptions() {
    $options = parent::defineOptions();
    $options['layout'] = [
      'contains' => [
        'layout_id' => [
          'default' => 'vefl_onecol',
        ],
        'regions' => [
          'default' => [],
        ],
        'widget_region' => [
          'default' => [],
        ],
      ],
    ];
    return $options;
  }

  /**
   * {@inheritdoc}
   */
  public function buildOptionsForm(&$form, FormStateInterface $form_state) {
    parent::buildOptionsForm($form, $form_state);
    $layout_id = $this->options['layout']['layout_id'];
    $layouts = $this->vefl
      ->getLayouts();

    // Outputs layout selectbox.
    $form['layout'] = [
      '#type' => 'details',
      '#title' => $this
        ->t('Layout settings'),
    ];
    $form['layout']['layout_id'] = [
      '#prefix' => '<div class="container-inline">',
      '#type' => 'select',
      '#options' => $this->vefl
        ->getLayoutOptions($layouts),
      '#title' => $this
        ->t('Layout'),
      '#default_value' => $layout_id,
    ];
    $form['layout']['change'] = [
      '#type' => 'submit',
      '#value' => $this
        ->t('Change'),
      '#submit' => [
        [
          $this,
          'updateRegions',
        ],
      ],
      '#suffix' => '</div>',
    ];
    $form['layout']['widget_region'] = $this
      ->getRegionElements($layout_id, $layouts);
  }

  /**
   * Set filters for regions.
   *
   * @param string $layout_id
   *   The layout id.
   * @param array $layouts
   *   The array of layouts.
   *
   * @return array
   *   Form elements.
   */
  private function getRegionElements($layout_id, array $layouts = []) {
    $element = [
      '#prefix' => '<div id="edit-block-region-wrapper">',
      '#suffix' => '</div>',
    ];

    // Outputs regions selectbox for each filter.
    $types = [
      'filters' => $this->view->display_handler
        ->getHandlers('filter'),
      'actions' => $this->vefl
        ->getFormActions(),
    ];
    $regions = [];
    foreach ($layouts[$layout_id]
      ->getRegions() as $region_id => $region) {
      $regions[$region_id] = $region['label'];
    }
    foreach ($types as $type => $fields) {
      foreach ($fields as $id => $filter) {
        if ($type == 'filters') {
          if (!$filter->options['exposed']) {
            continue;
          }
          elseif ($filter->options['is_grouped']) {
            $id = $filter->options['group_info']['identifier'];
            $label = $filter->options['group_info']['label'];
          }
          else {
            $id = $filter->options['expose']['identifier'];
            $label = $filter->options['expose']['label'];
          }
        }
        else {
          $label = $filter;
        }

        // Check if the operator is exposed for this filter.
        if (isset($filter->options['expose']['use_operator']) && $filter->options['expose']['use_operator']) {
          $operator_id = $filter->options['expose']['operator_id'];
          $element[$operator_id] = $this
            ->createSelectElementForVeflForm($operator_id, $this
            ->t('Expose operator') . ' - ' . $label, $regions);
        }
        $element[$id] = $this
          ->createSelectElementForVeflForm($id, $label, $regions);
      }
    }
    return $element;
  }

  /**
   * Form submission handler for ContentTranslationHandler::entityFormAlter().
   *
   * Takes care of content translation deletion.
   */
  public function updateRegions($form, FormStateInterface $form_state) {
    $view = $form_state
      ->get('view');
    $display_id = $form_state
      ->get('display_id');
    $display =& $view
      ->getExecutable()->displayHandlers
      ->get($display_id);

    // optionsOverride toggles the override of this section.
    $display
      ->optionsOverride($form, $form_state);
    $display
      ->submitOptionsForm($form, $form_state);
    $view
      ->cacheSet();
    $form_state
      ->set('rerender', TRUE);
    $form_state
      ->setRebuild();
  }

  /**
   * Alters the exposed form.
   *
   * @inheritdoc
   */
  public function exposedFormAlter(&$form, FormStateInterface $form_state) {
    parent::exposedFormAlter($form, $form_state);
    $view = $form_state
      ->get('view');
    $layout_id = $this->options['layout']['layout_id'];
    $widget_region = $this->options['layout']['widget_region'];
    $form['#vefl_configuration'] = [
      'layout' => [
        'id' => $layout_id,
        'settings' => [],
      ],
      'regions' => [],
    ];
    foreach ($widget_region as $field_name => $region) {
      $form['#vefl_configuration']['regions'][$region][] = $field_name;

      // Provides default wrapper settings for Display suite layout.
      if (substr($layout_id, 0, 3) == 'ds_') {
        $form['#vefl_configuration']['layout']['settings']['wrappers'][$region] = 'div';
      }
    }
    $form['#theme'] = $view
      ->buildThemeFunctions('vefl_views_exposed_form');
  }

  /**
   * Create form element VEFL form.
   *
   * @param string $element_id
   *   The form element id.
   * @param string $label
   *   The label for the form's element.
   * @param array $regions
   *   The array of regions.
   *
   * @return array
   *   Form element.
   */
  private function createSelectElementForVeflForm($element_id, $label, array $regions) {
    $element = [
      '#type' => 'select',
      '#title' => $label,
      '#options' => $regions,
    ];

    // Set default region for chosen layout.
    if (!empty($this->options['layout']['widget_region'][$element_id]) && !empty($regions[$this->options['layout']['widget_region'][$element_id]])) {
      $element['#default_value'] = $this->options['layout']['widget_region'][$element_id];
    }
    return $element;
  }

}