<?php

namespace Drupal\entity_reference_revisions;

use Drupal\Core\Entity\ContentEntityInterface;
use Drupal\Core\Entity\EntityStorageInterface;
use Drupal\Core\Entity\FieldableEntityInterface;
use Drupal\Core\Entity\RevisionableInterface;
use Drupal\Core\Entity\RevisionableStorageInterface;
use Drupal\Core\Field\FieldItemListInterface;
use Drupal\Core\Form\FormStateInterface;
use Drupal\Core\Field\FieldDefinitionInterface;
use Drupal\Core\Field\EntityReferenceFieldItemList;
use Drupal\Core\Field\EntityReferenceFieldItemListInterface;
use Drupal\entity_reference_revisions\Plugin\Field\FieldType\EntityReferenceRevisionsItem;

/**
 * Defines a item list class for entity reference fields.
 */
class EntityReferenceRevisionsFieldItemList extends EntityReferenceFieldItemList implements EntityReferenceFieldItemListInterface {

  /**
   * {@inheritdoc}
   */
  public function referencedEntities() {
    if ($this->isEmpty()) {
      return [];
    }

    $target_entities = $ids = $revision_ids = [];

    foreach ($this->list as $delta => $item) {
      assert($item instanceof EntityReferenceRevisionsItem);
      if ($item->isEntityLoaded()) {
        $target_entities[$delta] = $item->entity;
      }
      elseif ($item->target_revision_id !== NULL) {
        $ids[$item->target_revision_id] = $item->target_id;
        $revision_ids[$delta] = $item->target_revision_id;
      }
      elseif ($item->entity) {
        $target_entities[$delta] = $item->entity;
      }
    }
    if ($revision_ids) {
      $target_type = $this->getFieldDefinition()->getSetting('target_type');
      $storage = \Drupal::entityTypeManager()->getStorage($target_type);
      assert($storage instanceof RevisionableStorageInterface);

      // Drupal 11.3+ supports static and persistent revision caching, load revisions directly.
      if (\version_compare(\Drupal::VERSION, '11.2.99', '>')) {
        $revisions = $storage->loadMultipleRevisions($revision_ids);
        foreach ($revision_ids as $delta => $revision_id) {
          if (isset($revisions[$revision_id])) {
            $target_entities[$delta] = $revisions[$revision_id];
          }
        }
      }
      else {
        // Deprecated fallback for Drupal 11.2 and earlier that assumes that referenced entities are in the default
        // revision to benefit form the entity cache and only falls back to the revision if that assumption was wrong.
        $entities = [];
        foreach ($storage->loadMultiple($ids) as $entity) {
          if ($entity instanceof RevisionableInterface && in_array($entity->getRevisionId(), $revision_ids)) {
            unset($ids[$entity->getRevisionId()]);
            $entities[$entity->getRevisionId()] = $entity;
          }
        }
        if ($ids) {
          $entities += $storage->loadMultipleRevisions(array_flip($ids));
        }
        foreach ($revision_ids as $delta => $revision_id) {
          $entity = $entities[$revision_id] ?? NULL;
          if ($entity) {
            $target_entities[$delta] = $entity;
          }
        }

      }

      // Ensure the returned array is ordered by deltas.
      ksort($target_entities);
    }
    return $target_entities;
  }

  /**
   * {@inheritdoc}
   */
  public static function processDefaultValue($default_value, FieldableEntityInterface $entity, FieldDefinitionInterface $definition) {
    $default_value = parent::processDefaultValue($default_value, $entity, $definition);

    if ($default_value) {
      // Convert UUIDs to numeric IDs.
      $uuids = array();
      foreach ($default_value as $delta => $properties) {
        if (isset($properties['target_uuid'])) {
          $uuids[$delta] = $properties['target_uuid'];
        }
      }
      if ($uuids) {
        $target_type = $definition->getSetting('target_type');
        $entity_ids = \Drupal::entityQuery($target_type)
          ->condition('uuid', $uuids, 'IN')
          ->accessCheck(TRUE)
          ->execute();
        $entities = \Drupal::entityTypeManager()
          ->getStorage($target_type)
          ->loadMultiple($entity_ids);

        $entity_uuids = array();
        foreach ($entities as $id => $entity) {
          $entity_uuids[$entity->uuid()] = $id;
        }
        foreach ($uuids as $delta => $uuid) {
          if (isset($entity_uuids[$uuid])) {
            $default_value[$delta]['target_id'] = $entity_uuids[$uuid];
            unset($default_value[$delta]['target_uuid']);
          }
          else {
            unset($default_value[$delta]);
          }
        }
      }

      // Ensure we return consecutive deltas, in case we removed unknown UUIDs.
      $default_value = array_values($default_value);
    }

    return $default_value;
  }

  /**
   * {@inheritdoc}
   */
  public function defaultValuesFormSubmit(array $element, array &$form, FormStateInterface $form_state) {
    $default_value = parent::defaultValuesFormSubmit($element, $form, $form_state);

    // Convert numeric IDs to UUIDs to ensure config deployability.
    $ids = array();
    foreach ($default_value as $delta => $properties) {
      $ids[] = $properties['target_revision_id'];
    }

    $entities = array();
    foreach($ids as $id) {
      $entities[$id] = \Drupal::entityTypeManager()
        ->getStorage($this->getSetting('target_type'))
        ->loadRevision($id);
    }

    foreach ($default_value as $delta => $properties) {
      if (!empty($entities[$properties['target_revision_id']])) {
        $default_value[$delta] = array(
          'target_uuid' => $entities[$properties['target_revision_id']]->uuid(),
          'target_revision_id' => $properties['target_revision_id'],
        );
      }
    }
    return $default_value;
  }

  /**
   * {@inheritdoc}
   */
  public function hasAffectingChanges(FieldItemListInterface $original_items, $langcode) {
    // If there are fewer items, then it is a change.
    if (count($this) < count($original_items)) {
      return TRUE;
    }

    foreach ($this as $delta => $item) {
      // If this is a different entity, then it is an affecting change.
      if (!$original_items->offsetExists($delta) || $item->target_id != $original_items[$delta]->target_id) {
        return TRUE;
      }
      // If it is the same entity, only consider it as having affecting changes
      // if the target entity itself has changes.
      if ($item->entity && $item->entity->hasTranslation($langcode)) {
        $entity = $item->entity;
        assert($entity instanceof ContentEntityInterface);
        // Ensure it is compared against the loaded revision on 11.3+.
        if (version_compare(\Drupal::VERSION, '11.2.99', '>') && !$entity->getOriginal()) {
          $storage = \Drupal::entityTypeManager()->getStorage($entity->getEntityTypeId());
          assert($storage instanceof RevisionableStorageInterface);
          $entity->setOriginal($storage->loadRevisionUnchanged($entity->getLoadedRevisionId()));
        }
        return $entity->getTranslation($langcode)->hasTranslationChanges();
      }
    }

    return FALSE;
  }

}