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  <?php
namespace Drupal\diff;
use Drupal\Core\Field\FieldStorageDefinitionInterface;
use Drupal\Core\Form\FormStateInterface;
use Drupal\Core\Plugin\ContainerFactoryPluginInterface;
use Drupal\Core\Plugin\PluginBase;
use Symfony\Component\DependencyInjection\ContainerInterface;
use Drupal\Core\Entity\EntityTypeManagerInterface;
abstract class FieldDiffBuilderBase extends PluginBase implements FieldDiffBuilderInterface, ContainerFactoryPluginInterface {
  
  protected $configFactory;
  
  protected $entityTypeManager;
  
  protected $entityParser;
  
  public function __construct(array $configuration, $plugin_id, $plugin_definition, EntityTypeManagerInterface $entity_type_manager, DiffEntityParser $entity_parser) {
    $this->entityTypeManager = $entity_type_manager;
    $this->entityParser = $entity_parser;
    parent::__construct($configuration, $plugin_id, $plugin_definition);
    $this->configuration += $this
      ->defaultConfiguration();
  }
  
  public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
    return new static($configuration, $plugin_id, $plugin_definition, $container
      ->get('entity_type.manager'), $container
      ->get('diff.entity_parser'));
  }
  
  public function buildConfigurationForm(array $form, FormStateInterface $form_state) {
    $form['show_header'] = array(
      '#type' => 'checkbox',
      '#title' => $this
        ->t('Show field title'),
      '#weight' => -5,
      '#default_value' => $this->configuration['show_header'],
    );
    $form['markdown'] = array(
      '#type' => 'select',
      '#title' => $this
        ->t('Markdown callback'),
      '#default_value' => $this->configuration['markdown'],
      '#options' => array(
        'drupal_html_to_text' => $this
          ->t('Drupal HTML to Text'),
        'filter_xss' => $this
          ->t('Filter XSS (some tags)'),
        'filter_xss_all' => $this
          ->t('Filter XSS (all tags)'),
      ),
      '#description' => $this
        ->t('These provide ways to clean markup tags to make comparisons easier to read.'),
    );
    return $form;
  }
  
  public function validateConfigurationForm(array &$form, FormStateInterface $form_state) {
    
  }
  
  public function submitConfigurationForm(array &$form, FormStateInterface $form_state) {
    $this->configuration['show_header'] = $form_state
      ->getValue('show_header');
    $this->configuration['markdown'] = $form_state
      ->getValue('markdown');
  }
  
  public function defaultConfiguration() {
    return array(
      'show_header' => 1,
      'markdown' => 'drupal_html_to_text',
    );
  }
  
  public function getConfiguration() {
    return $this->configuration;
  }
  
  public function setConfiguration(array $configuration) {
    $this->configuration = $configuration + $this
      ->defaultConfiguration();
  }
  
  public static function isApplicable(FieldStorageDefinitionInterface $field_definition) {
    return TRUE;
  }
}