class ReorderDisplays

class ReorderDisplays extends ViewsFormBase {
  
  /**
   * {@inheritdoc}
   */
  public function getFormKey() {
    return 'reorder-displays';
  }
  
  /**
   * {@inheritdoc}
   */
  public function getFormId() {
    return 'views_ui_reorder_displays_form';
  }
  
  /**
   * {@inheritdoc}
   */
  public function buildForm(array $form, FormStateInterface $form_state) {
    /** @var \Drupal\views\ViewEntityInterface $view */
    $view = $form_state->get('view');
    $display_id = $form_state->get('display_id');
    $form['#title'] = $this->t('Reorder displays');
    $form['#section'] = 'reorder';
    $form['#action'] = Url::fromRoute('views_ui.form_reorder_displays', [
      'js' => 'nojs',
      'view' => $view->id(),
      'display_id' => $display_id,
    ])
      ->toString();
    $form['view'] = [
      '#type' => 'value',
      '#value' => $view,
    ];
    $displays = $view->get('display');
    $count = count($displays);
    // Sort the displays.
    uasort($displays, function ($display1, $display2) {
      return $display1['position'] <=> $display2['position'];
    });
    $form['displays'] = [
      '#type' => 'table',
      '#id' => 'reorder-displays',
      '#header' => [
        $this->t('Display'),
        $this->t('Weight'),
        $this->t('Remove'),
      ],
      '#empty' => $this->t('No displays available.'),
      '#tabledrag' => [
        [
          'action' => 'order',
          'relationship' => 'sibling',
          'group' => 'weight',
        ],
      ],
      '#tree' => TRUE,
      '#prefix' => '<div class="scroll" data-drupal-views-scroll>',
      '#suffix' => '</div>',
    ];
    foreach ($displays as $id => $display) {
      $form['displays'][$id] = [
        '#display' => $display,
        '#attributes' => [
          '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'] = [
        '#markup' => $display['display_title'],
      ];
      $form['displays'][$id]['weight'] = [
        '#type' => 'weight',
        '#value' => $display['position'],
        '#delta' => $count,
        '#title' => $this->t('Weight for @display', [
          '@display' => $display['display_title'],
        ]),
        '#title_display' => 'invisible',
        '#attributes' => [
          'class' => [
            'weight',
          ],
        ],
      ];
      $form['displays'][$id]['removed'] = [
        'checkbox' => [
          '#title' => $this->t('Remove @id', [
            '@id' => $id,
          ]),
          '#title_display' => 'invisible',
          '#type' => 'checkbox',
          '#id' => 'display-removed-' . $id,
          '#attributes' => [
            'class' => [
              'views-remove-checkbox',
            ],
          ],
          '#default_value' => !empty($display['deleted']),
        ],
        'link' => [
          '#type' => 'link',
          '#title' => new FormattableMarkup('<span>@text</span>', [
            '@text' => $this->t('Remove'),
          ]),
          '#url' => Url::fromRoute('<none>'),
          '#attributes' => [
            'id' => 'display-remove-link-' . $id,
            'class' => [
              'views-button-remove',
              'display-remove-link',
            ],
            'alt' => $this->t('Remove this display'),
            'title' => $this->t('Remove this display'),
          ],
        ],
        '#access' => $id !== 'default',
      ];
      if (!empty($display['deleted'])) {
        $form['displays'][$id]['deleted'] = [
          '#type' => 'value',
          '#value' => TRUE,
        ];
        $form['displays'][$id]['#attributes']['class'][] = 'hidden';
      }
    }
    $view->getStandardButtons($form, $form_state, 'views_ui_reorder_displays_form');
    return $form;
  }
  
  /**
   * {@inheritdoc}
   */
  public function submitForm(array &$form, FormStateInterface $form_state) {
    /** @var \Drupal\views_ui\ViewUI $view */
    $view = $form_state->get('view');
    $order = [];
    $user_input = $form_state->getUserInput();
    foreach ($user_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();
    $url = $view->toUrl('edit-form')
      ->setOption('fragment', 'views-tab-default');
    $form_state->setRedirectUrl($url);
  }

}