class AddItem

class AddItem extends ViewsFormBase {

  /**
   * Constucts a new AddItem object.
   */
  public function __construct($type = NULL) {
    $this
      ->setType($type);
  }

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

  /**
   * Overrides \Drupal\views_ui\Form\Ajax\ViewsFormBase::getForm().
   */
  public function getForm(ViewStorageInterface $view, $display_id, $js, $type = NULL) {
    $this
      ->setType($type);
    return parent::getForm($view, $display_id, $js);
  }

  /**
   * Implements \Drupal\Core\Form\FormInterface::getFormID().
   */
  public function getFormID() {
    return 'views_ui_add_item_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'];
    $type = $form_state['type'];
    $form = array(
      'options' => array(
        '#theme_wrappers' => array(
          'container',
        ),
        '#attributes' => array(
          'class' => array(
            'scroll',
          ),
        ),
      ),
    );
    $executable = $view
      ->get('executable');
    if (!$executable
      ->setDisplay($display_id)) {
      views_ajax_error(t('Invalid display id @display', array(
        '@display' => $display_id,
      )));
    }
    $display =& $executable->displayHandlers
      ->get($display_id);
    $types = ViewExecutable::viewsHandlerTypes();
    $ltitle = $types[$type]['ltitle'];
    $section = $types[$type]['plural'];
    if (!empty($types[$type]['type'])) {
      $type = $types[$type]['type'];
    }
    $form['#title'] = t('Add @type', array(
      '@type' => $ltitle,
    ));
    $form['#section'] = $display_id . 'add-item';

    // Add the display override dropdown.
    views_ui_standard_display_dropdown($form, $form_state, $section);

    // Figure out all the base tables allowed based upon what the relationships provide.
    $base_tables = $executable
      ->getBaseTables();
    $options = views_fetch_fields(array_keys($base_tables), $type, $display
      ->useGroupBy(), $form_state['type']);
    if (!empty($options)) {
      $form['override']['controls'] = array(
        '#theme_wrappers' => array(
          'container',
        ),
        '#id' => 'views-filterable-options-controls',
        '#attributes' => array(
          'class' => array(
            'container-inline',
          ),
        ),
      );
      $form['override']['controls']['options_search'] = array(
        '#type' => 'textfield',
        '#title' => t('Search'),
      );
      $groups = array(
        'all' => t('- All -'),
      );
      $form['override']['controls']['group'] = array(
        '#type' => 'select',
        '#title' => t('Type'),
        '#options' => array(),
      );
      $form['options']['name'] = array(
        '#prefix' => '<div class="views-radio-box form-checkboxes views-filterable-options">',
        '#suffix' => '</div>',
        '#tree' => TRUE,
        '#default_value' => 'all',
      );

      // Group options first to simplify the usage of #states.
      $grouped_options = array();
      foreach ($options as $key => $option) {
        $group = preg_replace('/[^a-z0-9]/', '-', strtolower($option['group']));
        $groups[$group] = $option['group'];
        $grouped_options[$group][$key] = $option;
        if (!empty($option['aliases']) && is_array($option['aliases'])) {
          foreach ($option['aliases'] as $id => $alias) {
            if (empty($alias['base']) || !empty($base_tables[$alias['base']])) {
              $copy = $option;
              $copy['group'] = $alias['group'];
              $copy['title'] = $alias['title'];
              if (isset($alias['help'])) {
                $copy['help'] = $alias['help'];
              }
              $group = preg_replace('/[^a-z0-9]/', '-', strtolower($copy['group']));
              $groups[$group] = $copy['group'];
              $grouped_options[$group][$key . '$' . $id] = $copy;
            }
          }
        }
      }
      foreach ($grouped_options as $group => $group_options) {
        $zebra = 0;
        foreach ($group_options as $key => $option) {
          $zebra_class = $zebra % 2 ? 'odd' : 'even';
          $form['options']['name'][$key] = array(
            '#type' => 'checkbox',
            '#title' => t('!group: !field', array(
              '!group' => $option['group'],
              '!field' => $option['title'],
            )),
            '#description' => $option['help'],
            '#return_value' => $key,
            '#prefix' => "<div class='{$zebra_class} filterable-option'>",
            '#suffix' => '</div>',
            '#states' => array(
              'visible' => array(
                array(
                  ':input[name="override[controls][group]"]' => array(
                    'value' => 'all',
                  ),
                ),
                array(
                  ':input[name="override[controls][group]"]' => array(
                    'value' => $group,
                  ),
                ),
              ),
            ),
          );
          $zebra++;
        }
      }
      $form['override']['controls']['group']['#options'] = $groups;
    }
    else {
      $form['options']['markup'] = array(
        '#markup' => '<div class="form-item">' . t('There are no @types available to add.', array(
          '@types' => $ltitle,
        )) . '</div>',
      );
    }

    // Add a div to show the selected items
    $form['selected'] = array(
      '#type' => 'item',
      '#markup' => '<div class="views-selected-options"></div>',
      '#title' => t('Selected') . ':',
      '#theme_wrappers' => array(
        'form_element',
        'views_ui_container',
      ),
      '#attributes' => array(
        'class' => array(
          'container-inline',
          'views-add-form-selected',
        ),
      ),
    );
    $view
      ->getStandardButtons($form, $form_state, 'views_ui_add_item_form', t('Add and configure @types', array(
      '@types' => $ltitle,
    )));

    // Remove the default submit function.
    $form['buttons']['submit']['#submit'] = array_filter($form['buttons']['submit']['#submit'], function ($var) {
      return !(is_array($var) && isset($var[1]) && $var[1] == 'standardSubmit');
    });
    $form['buttons']['submit']['#submit'][] = array(
      $view,
      'submitItemAdd',
    );
    return $form;
  }

}