<?php

/**
 * @file
 * Contains classy_paragraphs.module.
 */

use Drupal\field\FieldConfigInterface;
use Drupal\Core\Entity\EntityInterface;
use Drupal\Core\Entity\Display\EntityViewDisplayInterface;

/**
 * Implements hook_entity_view_alter().
 */
function classy_paragraphs_entity_view_alter(array &$build, EntityInterface $entity, EntityViewDisplayInterface $display) {

  // Find fields which are referencing classy_paragraphs.
  $class_fields = [];

  $fields = $entity->getFieldDefinitions();
  foreach($fields as $field) {
    if ($field instanceof FieldConfigInterface) {
      /** @var Drupal\field\Entity\FieldStorageConfig $field_storage */
      $field_storage = $field->getFieldStorageDefinition();

      $target = $field_storage->getSetting('target_type');
      if ($target == 'classy_paragraphs_style') {
        $class_fields[] = $field;
      }
    }
  }

  foreach($class_fields as $class_field) {
    $field_name = $class_field->get('field_name');
    if (!$entity->get($field_name)->isEmpty()) {

      $field = $entity->get($field_name);
      $classes = $field->referencedEntities();

      foreach($classes as $class) {
        $raw_classes = $class->getClasses();
        $array_classes = explode("\r\n", $raw_classes);
        if (!empty($array_classes)) {
          if(!empty($build['#attributes']['class'])) {
            $current_classes = $build['#attributes']['class'];
            $build['#attributes']['class'] = array_merge($current_classes, $array_classes);
          }
          else {
            $build['#attributes']['class'] = $array_classes;
          }
        }
      }
    }
  }
}