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);
    }

}