IssueYear.php

<?php

namespace Drupal\oaks_fields\Plugin\search_api\processor;

use Drupal\search_api\Datasource\DatasourceInterface;
use Drupal\search_api\Item\ItemInterface;
use Drupal\search_api\Processor\ProcessorPluginBase;
use Drupal\search_api\Processor\ProcessorProperty;
use Drupal\node\Entity\Node;
use Drupal\controlled_access_terms\EDTFUtils;

/**
 * Extract the year from an EDTF date
 *
 * @SearchApiProcessor(
 *   id = "oaks_fields_issue_year",
 *   label = @Translation("Issue Year"),
 *   description = @Translation("Gets the year from the EDTF date."),
 *   stages = {
 *     "add_properties" = 0,
 *   },
 *   locked = true,
 *   hidden = true,
 * )
 */
class IssueYear extends ProcessorPluginBase {

  /**
   * {@inheritdoc}
   */
  public function getPropertyDefinitions(DatasourceInterface $datasource = NULL) {
    $properties = [];

    if (!$datasource) {
      $definition = [
        'label' => $this->t('OAKS Issue Year'),
        'description' => $this->t('The year the item was published'),
        'type' => 'integer',
        'processor_id' => $this->getPluginId(),
      ];
      $properties['oaks_issue_year'] = new ProcessorProperty($definition);
    }

    return $properties;
  }

  /**
   * {@inheritdoc}
   */
  public function addFieldValues(ItemInterface $item) {
    // find the URI of the entity being added to the search API
    // via the search API's item ID (e.g. entity:node/1:en)
    $components = explode(':', $item->getId());
    array_shift($components);
    $uri = array_shift($components);
    $components = explode('/', $uri);

    // if this is a node, load it
    if (count($components) == 2 && $components[0] === 'node') {
      // @todo is there a better way to get the node entity than loading it again?
      $node = Node::load($components[1]);

      // if we the node, and it has an issued date, add it to the index
      if ($node
        && $node->hasField('field_edtf_date_issued')
        && !$node->field_edtf_date_issued->isEmpty()) {

        $date = $node->field_edtf_date_issued->value;
        $iso = EDTFUtils::iso8601Value($date);
        $components = explode('-', $iso);
        $year = array_shift($components);
        if (is_numeric($year)) {
          $fields = $item->getFields(FALSE);
          $fields = $this->getFieldsHelper()
            ->filterForPropertyPath($fields, NULL, 'oaks_issue_year');
          foreach ($fields as $field) {
            $field->addValue($year);
          }
        }
      }
    }
  }
}