class ManyToOne

class ManyToOne extends InOperator {
  
  /**
   * @var \Drupal\views\ManyToOneHelper
   *
   * Stores the Helper object which handles the many_to_one complexity.
   */
  public $helper = NULL;
  
  /**
   * {@inheritdoc}
   */
  public function init(ViewExecutable $view, DisplayPluginBase $display, ?array &$options = NULL) {
    parent::init($view, $display, $options);
    $this->helper = new ManyToOneHelper($this);
  }
  
  /**
   * {@inheritdoc}
   */
  protected function defineOptions() {
    $options = parent::defineOptions();
    $options['operator']['default'] = 'or';
    $options['value']['default'] = [];
    if (isset($this->helper)) {
      $this->helper
        ->defineOptions($options);
    }
    else {
      $helper = new ManyToOneHelper($this);
      $helper->defineOptions($options);
    }
    return $options;
  }
  
  /**
   * {@inheritdoc}
   */
  public function operators() {
    $operators = [
      'or' => [
        'title' => $this->t('Is one of'),
        'short' => $this->t('or'),
        'short_single' => $this->t('='),
        'method' => 'opHelper',
        'values' => 1,
        'ensure_my_table' => 'helper',
      ],
      'and' => [
        'title' => $this->t('Is all of'),
        'short' => $this->t('and'),
        'short_single' => $this->t('='),
        'method' => 'opHelper',
        'values' => 1,
        'ensure_my_table' => 'helper',
      ],
      'not' => [
        'title' => $this->t('Is none of'),
        'short' => $this->t('not'),
        'short_single' => $this->t('<>'),
        'method' => 'opHelper',
        'values' => 1,
        'ensure_my_table' => 'helper',
      ],
    ];
    // If the definition allows for the empty operator, add it.
    if (!empty($this->definition['allow empty'])) {
      $operators += [
        'empty' => [
          'title' => $this->t('Is empty (NULL)'),
          'method' => 'opEmpty',
          'short' => $this->t('empty'),
          'values' => 0,
        ],
        'not empty' => [
          'title' => $this->t('Is not empty (NOT NULL)'),
          'method' => 'opEmpty',
          'short' => $this->t('not empty'),
          'values' => 0,
        ],
      ];
    }
    return $operators;
  }
  
  /**
   * The default form type.
   *
   * @var string
   */
  protected $valueFormType = 'select';
  
  /**
   * {@inheritdoc}
   */
  protected function valueForm(&$form, FormStateInterface $form_state) {
    parent::valueForm($form, $form_state);
    if (!$form_state->get('exposed')) {
      $this->helper
        ->buildOptionsForm($form, $form_state);
    }
  }
  
  /**
   * {@inheritdoc}
   */
  public function ensureMyTable() {
    // Defer to helper if the operator specifies it.
    $info = $this->operators();
    if (isset($info[$this->operator]['ensure_my_table']) && $info[$this->operator]['ensure_my_table'] == 'helper') {
      return $this->helper
        ->ensureMyTable();
    }
    return parent::ensureMyTable();
  }
  
  /**
   * Adds a filter.
   */
  protected function opHelper() {
    if (empty($this->value)) {
      return;
    }
    // Form API returns unchecked options in the form of option_id => 0. This
    // breaks the generated query for "is all of" filters so we remove them.
    $this->value = array_filter($this->value, [
      static::class,
      'arrayFilterZero',
    ]);
    $this->helper
      ->addFilter();
  }

}