class Term

class Term extends FieldableEntity {
  
  /**
   * {@inheritdoc}
   */
  public function query() {
    $query = $this->select('taxonomy_term_data', 'td')
      ->fields('td')
      ->distinct()
      ->orderBy('tid');
    $query->leftJoin('taxonomy_vocabulary', 'tv', '[td].[vid] = [tv].[vid]');
    $query->addField('tv', 'machine_name');
    if ($this->getDatabase()
      ->schema()
      ->fieldExists('taxonomy_vocabulary', 'i18n_mode')) {
      $query->addField('tv', 'i18n_mode');
    }
    if (isset($this->configuration['bundle'])) {
      $query->condition('tv.machine_name', (array) $this->configuration['bundle'], 'IN');
    }
    return $query;
  }
  
  /**
   * {@inheritdoc}
   */
  public function fields() {
    $fields = [
      'tid' => $this->t('The term ID.'),
      'vid' => $this->t('Existing term VID'),
      'machine_name' => $this->t('Vocabulary machine name'),
      'name' => $this->t('The name of the term.'),
      'description' => $this->t('The term description.'),
      'weight' => $this->t('Weight'),
      'parent' => $this->t("The Drupal term IDs of the term's parents."),
      'format' => $this->t("Format of the term description."),
    ];
    return $fields;
  }
  
  /**
   * {@inheritdoc}
   */
  public function prepareRow(Row $row) {
    $tid = $row->getSourceProperty('tid');
    $vocabulary = $row->getSourceProperty('machine_name');
    $default_language = (array) $this->variableGet('language_default', [
      'language' => 'en',
    ]);
    // If this entity was translated using Entity Translation, we need to get
    // its source language to get the field values in the right language.
    // The translations will be migrated by the d7_node_entity_translation
    // migration.
    $translatable_vocabularies = array_keys(array_filter($this->variableGet('entity_translation_taxonomy', [])));
    $entity_translatable = $this->isEntityTranslatable('taxonomy_term') && in_array($vocabulary, $translatable_vocabularies, TRUE);
    if ($entity_translatable) {
      $source_language = $this->getEntityTranslationSourceLanguage('taxonomy_term', $tid);
      $language = $entity_translatable && $source_language ? $source_language : $default_language['language'];
    }
    // If this is an i18n translation use the default language when i18n_mode
    // is localized.
    if ($row->get('i18n_mode')) {
      $language = $row->get('i18n_mode') === '1' ? $default_language['language'] : $row->get('language');
    }
    $language = $language ?? $default_language['language'];
    $row->setSourceProperty('language', $language);
    // Get Field API field values.
    foreach ($this->getFields('taxonomy_term', $vocabulary) as $field_name => $field) {
      // Ensure we're using the right language if the entity and the field are
      // translatable.
      $field_language = $entity_translatable && $field['translatable'] ? $language : NULL;
      $row->setSourceProperty($field_name, $this->getFieldValues('taxonomy_term', $field_name, $tid, NULL, $field_language));
    }
    // Find parents for this row.
    $parents = $this->select('taxonomy_term_hierarchy', 'th')
      ->fields('th', [
      'parent',
      'tid',
    ])
      ->condition('tid', $row->getSourceProperty('tid'))
      ->execute()
      ->fetchCol();
    $row->setSourceProperty('parent', $parents);
    // If the term name or term description were replaced by real fields using
    // the Drupal 7 Title module, use the fields value instead of the term name
    // or term description.
    if ($this->moduleExists('title')) {
      $name_field = $row->getSourceProperty('name_field');
      if (isset($name_field[0]['value'])) {
        $row->setSourceProperty('name', $name_field[0]['value']);
      }
      $description_field = $row->getSourceProperty('description_field');
      if (isset($description_field[0]['value'])) {
        $row->setSourceProperty('description', $description_field[0]['value']);
      }
      if (isset($description_field[0]['format'])) {
        $row->setSourceProperty('format', $description_field[0]['format']);
      }
    }
    return parent::prepareRow($row);
  }
  
  /**
   * {@inheritdoc}
   */
  public function getIds() {
    $ids['tid']['type'] = 'integer';
    return $ids;
  }

}