CustomJson.php

<?php

namespace Drupal\custom_migrate\Plugin\migrate_plus\data_parser;

use Drupal\migrate_plus\Plugin\migrate_plus\data_parser\Json;

/**
 * Obtain JSON data for migration.
 *
 * @DataParser(
 *   id = "custom_json",
 *   title = @Translation("Custom JSON")
 * )
 */
class CustomJson extends Json {

  /**
   * {@inheritdoc}
   */
  protected function getSourceData($url) {
    $response = $this->getDataFetcherPlugin()->getResponseContent($url);

    // Convert objects to associative arrays.
    $source_data = json_decode($response, TRUE);

    // If json_decode() has returned NULL, it might be that the data isn't
    // valid utf8 - see http://php.net/manual/en/function.json-decode.php#86997.
    if (is_null($source_data)) {
      $utf8response = utf8_encode($response);
      $source_data = json_decode($utf8response, TRUE);
    }

    // Code to modify the source data as per Drupal needs.
    if (is_array($source_data)) {
      $source_data = $this->processSourceData($source_data);
    }

    // In migration config, we will use our new source instead of
    // original source from JSON.
    // For individual paragraphs source would be 'scopes' and
    // for main content where we import multiple values using 
    // migration_loop, we will use scopes inside data in fields
    // and id for iterator.
    $selectors = explode('/', trim($this->itemSelector, '/'));
    foreach ($selectors as $selector) {
      if (!empty($selector)) {
        $source_data = $source_data[$selector];
      }
    }

    return $source_data;
  }

  /**
   * Process source data.
   *
   * Add scopes as separate root element and scope data with proper ids in
   * main content.
   *
   * @param array $source_data
   *   Source data.
   *
   * @return array
   *   Processed source data to add scopes as separate root element and scopes
   *   data with proper ids in main content.
   */
  protected function processSourceData(array $source_data): array {
    $scopes = [];

    foreach ($source_data['data'] as &$row) {
      $id = $row['id'];
      foreach ($row['scope'] ?? [] as $delta => $data) {
        // Unique ID for each multi-value data item.
        $scope_id = $id . '-' . $delta;
        $scope = ['id' => $scope_id];

        foreach ($data as $item) {
          $scope[$item['key']] = $item['value'];
        }

        // This will be used in migration of individual paragraphs.
        $scopes[] = $scope;

        // This will be used in migration of main content.
        $row['scopes'][] = [
          'id' => $scope_id,
        ];
      }
    }

    $source_data['scopes'] = $scopes;

    return $source_data;
  }

}