class Attachment

class Attachment extends DisplayPluginBase {
    
    /**
     * Whether the display allows the use of a pager or not.
     *
     * @var bool
     */
    protected $usesPager = FALSE;
    protected function defineOptions() {
        $options = parent::defineOptions();
        $options['displays'] = [
            'default' => [],
        ];
        $options['attachment_position'] = [
            'default' => 'before',
        ];
        $options['inherit_arguments'] = [
            'default' => TRUE,
        ];
        $options['inherit_exposed_filters'] = [
            'default' => FALSE,
        ];
        $options['inherit_pager'] = [
            'default' => FALSE,
        ];
        $options['render_pager'] = [
            'default' => FALSE,
        ];
        return $options;
    }
    public function execute() {
        return $this->view
            ->render($this->display['id']);
    }
    public function attachmentPositions($position = NULL) {
        $positions = [
            'before' => $this->t('Before'),
            'after' => $this->t('After'),
            'both' => $this->t('Both'),
        ];
        if ($position) {
            return $positions[$position];
        }
        return $positions;
    }
    
    /**
     * Provide the summary for attachment options in the views UI.
     *
     * This output is returned as an array.
     */
    public function optionsSummary(&$categories, &$options) {
        // It is very important to call the parent function here:
        parent::optionsSummary($categories, $options);
        $categories['attachment'] = [
            'title' => $this->t('Attachment settings'),
            'column' => 'second',
            'build' => [
                '#weight' => -10,
            ],
        ];
        $displays = array_filter($this->getOption('displays'));
        if (count($displays) > 1) {
            $attach_to = $this->t('Multiple displays');
        }
        elseif (count($displays) == 1) {
            $display = array_shift($displays);
            if ($display = $this->view->storage
                ->getDisplay($display)) {
                $attach_to = $display['display_title'];
            }
        }
        if (!isset($attach_to)) {
            $attach_to = $this->t('Not defined');
        }
        $options['displays'] = [
            'category' => 'attachment',
            'title' => $this->t('Attach to'),
            'value' => $attach_to,
        ];
        $options['attachment_position'] = [
            'category' => 'attachment',
            'title' => $this->t('Attachment position'),
            'value' => $this->attachmentPositions($this->getOption('attachment_position')),
        ];
        $options['inherit_arguments'] = [
            'category' => 'attachment',
            'title' => $this->t('Inherit contextual filters'),
            'value' => $this->getOption('inherit_arguments') ? $this->t('Yes') : $this->t('No'),
        ];
        $options['inherit_exposed_filters'] = [
            'category' => 'attachment',
            'title' => $this->t('Inherit exposed filters'),
            'value' => $this->getOption('inherit_exposed_filters') ? $this->t('Yes') : $this->t('No'),
        ];
        $options['inherit_pager'] = [
            'category' => 'pager',
            'title' => $this->t('Inherit pager'),
            'value' => $this->getOption('inherit_pager') ? $this->t('Yes') : $this->t('No'),
        ];
        $options['render_pager'] = [
            'category' => 'pager',
            'title' => $this->t('Render pager'),
            'value' => $this->getOption('render_pager') ? $this->t('Yes') : $this->t('No'),
        ];
    }
    
    /**
     * Provide the default form for setting options.
     */
    public function buildOptionsForm(&$form, FormStateInterface $form_state) {
        // It is very important to call the parent function here:
        parent::buildOptionsForm($form, $form_state);
        switch ($form_state->get('section')) {
            case 'inherit_arguments':
                $form['#title'] .= $this->t('Inherit contextual filters');
                $form['inherit_arguments'] = [
                    '#type' => 'checkbox',
                    '#title' => $this->t('Inherit'),
                    '#description' => $this->t('Should this display inherit its contextual filter values from the parent display to which it is attached?'),
                    '#default_value' => $this->getOption('inherit_arguments'),
                ];
                break;
            case 'inherit_exposed_filters':
                $form['#title'] .= $this->t('Inherit exposed filters');
                $form['inherit_exposed_filters'] = [
                    '#type' => 'checkbox',
                    '#title' => $this->t('Inherit'),
                    '#description' => $this->t('Should this display inherit its exposed filter values from the parent display to which it is attached?'),
                    '#default_value' => $this->getOption('inherit_exposed_filters'),
                ];
                break;
            case 'inherit_pager':
                $form['#title'] .= $this->t('Inherit pager');
                $form['inherit_pager'] = [
                    '#type' => 'checkbox',
                    '#title' => $this->t('Inherit'),
                    '#description' => $this->t('Should this display inherit its paging values from the parent display to which it is attached?'),
                    '#default_value' => $this->getOption('inherit_pager'),
                ];
                break;
            case 'render_pager':
                $form['#title'] .= $this->t('Render pager');
                $form['render_pager'] = [
                    '#type' => 'checkbox',
                    '#title' => $this->t('Render'),
                    '#description' => $this->t('Should this display render the pager values? This is only meaningful if inheriting a pager.'),
                    '#default_value' => $this->getOption('render_pager'),
                ];
                break;
            case 'attachment_position':
                $form['#title'] .= $this->t('Position');
                $form['attachment_position'] = [
                    '#title' => $this->t('Position'),
                    '#type' => 'radios',
                    '#description' => $this->t('Attach before or after the parent display?'),
                    '#options' => $this->attachmentPositions(),
                    '#default_value' => $this->getOption('attachment_position'),
                ];
                break;
            case 'displays':
                $form['#title'] .= $this->t('Attach to');
                $displays = [];
                foreach ($this->view->storage
                    ->get('display') as $display_id => $display) {
                    if ($this->view->displayHandlers
                        ->has($display_id) && $this->view->displayHandlers
                        ->get($display_id)
                        ->acceptAttachments()) {
                        $displays[$display_id] = $display['display_title'];
                    }
                }
                $form['displays'] = [
                    '#title' => $this->t('Displays'),
                    '#type' => 'checkboxes',
                    '#description' => $this->t('Select which display or displays this should attach to.'),
                    '#options' => array_map('\\Drupal\\Component\\Utility\\Html::escape', $displays),
                    '#default_value' => $this->getOption('displays'),
                ];
                break;
        }
    }
    
    /**
     * Perform any necessary changes to the form values prior to storage.
     *
     * There is no need for this function to actually store the data.
     */
    public function submitOptionsForm(&$form, FormStateInterface $form_state) {
        // It is very important to call the parent function here:
        parent::submitOptionsForm($form, $form_state);
        $section = $form_state->get('section');
        switch ($section) {
            case 'displays':
                $form_state->setValue($section, array_filter($form_state->getValue($section)));
            case 'inherit_arguments':
            case 'inherit_pager':
            case 'render_pager':
            case 'inherit_exposed_filters':
            case 'attachment_position':
                $this->setOption($section, $form_state->getValue($section));
                break;
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function attachTo(ViewExecutable $view, $display_id, array &$build) {
        $displays = $this->getOption('displays');
        if (empty($displays[$display_id])) {
            return;
        }
        if (!$this->access()) {
            return;
        }
        $args = $this->getOption('inherit_arguments') ? $this->view->args : [];
        $view->setArguments($args);
        $view->setDisplay($this->display['id']);
        if ($this->getOption('inherit_pager')) {
            $view->display_handler->usesPager = $this->view->displayHandlers
                ->get($display_id)
                ->usesPager();
            $view->display_handler
                ->setOption('pager', $this->view->displayHandlers
                ->get($display_id)
                ->getOption('pager'));
        }
        $attachment = $view->buildRenderable($this->display['id'], $args);
        switch ($this->getOption('attachment_position')) {
            case 'before':
                $this->view->attachment_before[] = $attachment;
                break;
            case 'after':
                $this->view->attachment_after[] = $attachment;
                break;
            case 'both':
                $this->view->attachment_before[] = $attachment;
                $this->view->attachment_after[] = $attachment;
                break;
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function usesExposed() {
        // Attachment displays only use exposed widgets if they are set to inherit
        // the exposed filter settings of their parent display.
        if (!empty($this->options['inherit_exposed_filters']) && parent::usesExposed()) {
            return TRUE;
        }
        return FALSE;
    }
    
    /**
     * {@inheritdoc}
     */
    public function displaysExposed() {
        // If an attachment is set to inherit the exposed filter settings from its
        // parent display, then don't render and display a second set of exposed
        // filter widgets.
        return $this->options['inherit_exposed_filters'] ? FALSE : TRUE;
    }
    public function renderPager() {
        return $this->usesPager() && $this->getOption('render_pager');
    }

}