LanguageCombination.php

<?php

namespace Drupal\tmgmt_language_combination\Plugin\Field\FieldType;

use Drupal\Core\Field\FieldItemBase;
use Drupal\Core\Field\FieldStorageDefinitionInterface;
use Drupal\Core\TypedData\DataDefinition;
use Drupal\language\Entity\ConfigurableLanguage;

/**
 * Plugin implementation of the 'tmgmt_language_combination' field type.
 *
 * @FieldType(
 *   id = "tmgmt_language_combination",
 *   label = @Translation("Language Combination"),
 *   description = @Translation("Allows the definition of language combinations (e.g. 'From english to german')."),
 *   default_widget = "tmgmt_language_combination_default",
 *   default_formatter = "tmgmt_language_combination_default",
 *   constraints = {"TMGMTLanguageCombination" = {}}
 * )
 */
class LanguageCombination extends FieldItemBase {

  /**
   * {@inheritdoc}
   */
  public static function propertyDefinitions(FieldStorageDefinitionInterface $field) {
    $property_definitions['language_from'] = DataDefinition::create('string')
      ->setLabel(t('From language'));
    $property_definitions['language_to'] = DataDefinition::create('string')
      ->setLabel(t('To language'));
    return $property_definitions;
  }

  /**
   * {@inheritdoc}
   */
  public static function schema(FieldStorageDefinitionInterface $field) {
    return array(
      'columns' => array(
        'language_from' => array(
          'description' => 'The langcode of the language from which the user is able to translate.',
          'type' => 'varchar',
          'length' => 10,
        ),
        'language_to' => array(
          'description' => 'The langcode of the language to which the user is able to translate.',
          'type' => 'varchar',
          'length' => 10,
        ),
      ),
      'indexes' => array(
        'language' => array(
          'language_from',
          'language_to',
        ),
      ),
    );
  }

  /**
   * {@inheritdoc}
   */
  public function isEmpty() {
    if (empty($this->language_from) || empty($this->language_to) || $this->language_from == '_none' || $this->language_to == '_none') {
      return TRUE;
    }
    return FALSE;
  }

  /**
   * {@inheritdoc}
   */
  public function preSave() {
    parent::preSave();

    // In case the skill languages is not know to the system, install them.
    $languages = \Drupal::languageManager()
      ->getLanguages();
    if (!isset($languages[$this->language_from])) {
      $language = ConfigurableLanguage::createFromLangcode($this->language_from);
      $language
        ->save();
    }
    if (!isset($languages[$this->language_to])) {
      $language = ConfigurableLanguage::createFromLangcode($this->language_to);
      $language
        ->save();
    }
  }

}