class ReorderDisplays

class ReorderDisplays extends ViewsFormBase {

  /**
   * Implements \Drupal\views_ui\Form\Ajax\ViewsFormInterface::getFormKey().
   */
  public function getFormKey() {
    return 'reorder-displays';
  }

  /**
   * Implements \Drupal\Core\Form\FormInterface::getFormID().
   */
  public function getFormID() {
    return 'views_ui_reorder_displays_form';
  }

  /**
   * Implements \Drupal\Core\Form\FormInterface::buildForm().
   */
  public function buildForm(array $form, array &$form_state) {
    $view = $form_state['view'];
    $display_id = $form_state['display_id'];
    $form['#title'] = t('Reorder displays');
    $form['#section'] = 'reorder';
    $form['#action'] = url('admin/structure/views/nojs/reorder-displays/' . $view
      ->id() . '/' . $display_id);
    $form['view'] = array(
      '#type' => 'value',
      '#value' => $view,
    );
    $displays = $view
      ->get('display');
    $count = count($displays);

    // Sort the displays.
    uasort($displays, function ($display1, $display2) {
      if ($display1['position'] != $display2['position']) {
        return $display1['position'] < $display2['position'] ? -1 : 1;
      }
      return 0;
    });
    $form['displays'] = array(
      '#type' => 'table',
      '#id' => 'reorder-displays',
      '#header' => array(
        t('Display'),
        t('Weight'),
        t('Remove'),
      ),
      '#empty' => t('No displays available.'),
      '#tabledrag' => array(
        array(
          'order',
          'sibling',
          'weight',
        ),
      ),
      '#tree' => TRUE,
      '#prefix' => '<div class="scroll">',
      '#suffix' => '</div>',
    );
    foreach ($displays as $id => $display) {
      $form['displays'][$id] = array(
        '#display' => $display,
        '#attributes' => array(
          'id' => 'display-row-' . $id,
        ),
        '#weight' => $display['position'],
      );

      // Only make row draggable if it's not the default display.
      if ($id !== 'default') {
        $form['displays'][$id]['#attributes']['class'][] = 'draggable';
      }
      $form['displays'][$id]['title'] = array(
        '#markup' => $display['display_title'],
      );
      $form['displays'][$id]['weight'] = array(
        '#type' => 'weight',
        '#value' => $display['position'],
        '#delta' => $count,
        '#title' => t('Weight for @display', array(
          '@display' => $display['display_title'],
        )),
        '#title_display' => 'invisible',
        '#attributes' => array(
          'class' => array(
            'weight',
          ),
        ),
      );
      $form['displays'][$id]['removed'] = array(
        'checkbox' => array(
          '#type' => 'checkbox',
          '#id' => 'display-removed-' . $id,
          '#attributes' => array(
            'class' => array(
              'views-remove-checkbox',
            ),
          ),
          '#default_value' => !empty($display['deleted']),
        ),
        'link' => array(
          '#type' => 'link',
          '#title' => '<span>' . t('Remove') . '</span>',
          '#href' => 'javascript:void()',
          '#options' => array(
            'html' => TRUE,
          ),
          '#attributes' => array(
            'id' => 'display-remove-link-' . $id,
            'class' => array(
              'views-button-remove',
              'display-remove-link',
            ),
            'alt' => t('Remove this display'),
            'title' => t('Remove this display'),
          ),
        ),
        '#access' => $id !== 'default',
      );
      if (!empty($display['deleted'])) {
        $form['displays'][$id]['deleted'] = array(
          '#type' => 'value',
          '#value' => TRUE,
        );
        $form['displays'][$id]['#attributes']['class'][] = 'element-hidden';
      }
    }
    $view
      ->getStandardButtons($form, $form_state, 'views_ui_reorder_displays_form');
    return $form;
  }

  /**
   * Overrides \Drupal\views_ui\Form\Ajax\ViewsFormBase::submitForm().
   */
  public function submitForm(array &$form, array &$form_state) {
    $view = $form_state['view'];
    $order = array();
    foreach ($form_state['input']['displays'] as $display => $info) {

      // Add each value that is a field with a weight to our list, but only if
      // it has had its 'removed' checkbox checked.
      if (is_array($info) && isset($info['weight']) && empty($info['removed']['checkbox'])) {
        $order[$display] = $info['weight'];
      }
    }

    // Sort the order array.
    asort($order);

    // Remove the default display from ordering.
    unset($order['default']);

    // Increment up positions.
    $position = 1;
    foreach (array_keys($order) as $display) {
      $order[$display] = $position++;
    }

    // Setting up position and removing deleted displays.
    $displays = $view
      ->get('display');
    foreach ($displays as $display_id => &$display) {

      // Don't touch the default.
      if ($display_id === 'default') {
        $display['position'] = 0;
        continue;
      }
      if (isset($order[$display_id])) {
        $display['position'] = $order[$display_id];
      }
      else {
        $display['deleted'] = TRUE;
      }
    }
    $view
      ->set('display', $displays);

    // Store in cache.
    $view
      ->cacheSet();
    $form_state['redirect'] = array(
      'admin/structure/views/view/' . $view
        ->id() . '/edit',
      array(
        'fragment' => 'views-tab-default',
      ),
    );
  }

}