class ConfigDependencies

class ConfigDependencies implements ContainerInjectionInterface {

  /**
   * The serialization format providers, keyed by format.
   *
   * @var string[]
   */
  protected $formatProviders;

  /**
   * The authentication providers, keyed by ID.
   *
   * @var string[]
   */
  protected $authProviders;

  /**
   * Creates a new ConfigDependencies instance.
   *
   * @param string[] $format_providers
   *   The serialization format providers, keyed by format.
   * @param string[] $auth_providers
   *   The authentication providers, keyed by ID.
   */
  public function __construct(array $format_providers, array $auth_providers) {
    $this->formatProviders = $format_providers;
    $this->authProviders = $auth_providers;
  }

  /**
   * {@inheritdoc}
   */
  public static function create(ContainerInterface $container) {
    return new static($container
      ->getParameter('serializer.format_providers'), $container
      ->getParameter('authentication_providers'));
  }

  /**
   * Calculates dependencies of a specific rest resource configuration.
   *
   * This function returns dependencies in a non-sorted, non-unique manner. It
   * is therefore the caller's responsibility to sort and remove duplicates
   * from the result prior to saving it with the configuration or otherwise
   * using it in a way that requires that. For example,
   * \Drupal\rest\Entity\RestResourceConfig::calculateDependencies() does this
   * via its \Drupal\Core\Entity\DependencyTrait::addDependency() method.
   *
   * @param \Drupal\rest\RestResourceConfigInterface $rest_config
   *   The rest configuration.
   *
   * @return string[][]
   *   Dependencies keyed by dependency type.
   *
   * @see \Drupal\rest\Entity\RestResourceConfig::calculateDependencies()
   */
  public function calculateDependencies(RestResourceConfigInterface $rest_config) {
    $granularity = $rest_config
      ->get('granularity');

    // Dependency calculation is the same for either granularity, the most
    // notable difference is that for the 'resource' granularity, the same
    // authentication providers and formats are supported for every method.
    switch ($granularity) {
      case RestResourceConfigInterface::METHOD_GRANULARITY:
        $methods = $rest_config
          ->getMethods();
        break;
      case RestResourceConfigInterface::RESOURCE_GRANULARITY:
        $methods = array_slice($rest_config
          ->getMethods(), 0, 1);
        break;
      default:
        throw new \InvalidArgumentException('Invalid granularity specified.');
    }

    // The dependency lists for authentication providers and formats
    // generated on container build.
    $dependencies = [];
    foreach ($methods as $request_method) {

      // Add dependencies based on the supported authentication providers.
      foreach ($rest_config
        ->getAuthenticationProviders($request_method) as $auth) {
        if (isset($this->authProviders[$auth])) {
          $module_name = $this->authProviders[$auth];
          $dependencies['module'][] = $module_name;
        }
      }

      // Add dependencies based on the supported authentication formats.
      foreach ($rest_config
        ->getFormats($request_method) as $format) {
        if (isset($this->formatProviders[$format])) {
          $module_name = $this->formatProviders[$format];
          $dependencies['module'][] = $module_name;
        }
      }
    }
    return $dependencies;
  }

  /**
   * Informs the entity that entities it depends on will be deleted.
   *
   * @param \Drupal\rest\RestResourceConfigInterface $rest_config
   *   The rest configuration.
   * @param array $dependencies
   *   An array of dependencies that will be deleted keyed by dependency type.
   *   Dependency types are, for example, entity, module and theme.
   *
   * @return bool
   *   TRUE if the entity has been changed as a result, FALSE if not.
   *
   * @see \Drupal\Core\Config\Entity\ConfigEntityInterface::onDependencyRemoval()
   */
  public function onDependencyRemoval(RestResourceConfigInterface $rest_config, array $dependencies) {
    $granularity = $rest_config
      ->get('granularity');
    switch ($granularity) {
      case RestResourceConfigInterface::METHOD_GRANULARITY:
        return $this
          ->onDependencyRemovalForMethodGranularity($rest_config, $dependencies);
      case RestResourceConfigInterface::RESOURCE_GRANULARITY:
        return $this
          ->onDependencyRemovalForResourceGranularity($rest_config, $dependencies);
      default:
        throw new \InvalidArgumentException('Invalid granularity specified.');
    }
  }

  /**
   * Informs the entity that entities it depends on will be deleted.
   *
   * @param \Drupal\rest\RestResourceConfigInterface $rest_config
   *   The rest configuration.
   * @param array $dependencies
   *   An array of dependencies that will be deleted keyed by dependency type.
   *   Dependency types are, for example, entity, module and theme.
   *
   * @return bool
   *   TRUE if the entity has been changed as a result, FALSE if not.
   */
  protected function onDependencyRemovalForMethodGranularity(RestResourceConfigInterface $rest_config, array $dependencies) {
    $changed = FALSE;

    // Only module-related dependencies can be fixed. All other types of
    // dependencies cannot, because they were not generated based on supported
    // authentication providers or formats.
    if (isset($dependencies['module'])) {

      // Try to fix dependencies.
      $removed_auth = array_keys(array_intersect($this->authProviders, $dependencies['module']));
      $removed_formats = array_keys(array_intersect($this->formatProviders, $dependencies['module']));
      $configuration_before = $configuration = $rest_config
        ->get('configuration');
      if (!empty($removed_auth) || !empty($removed_formats)) {

        // Try to fix dependency problems by removing affected
        // authentication providers and formats.
        foreach (array_keys($rest_config
          ->get('configuration')) as $request_method) {
          foreach ($removed_formats as $format) {
            if (in_array($format, $rest_config
              ->getFormats($request_method), TRUE)) {
              $configuration[$request_method]['supported_formats'] = array_diff($configuration[$request_method]['supported_formats'], $removed_formats);
            }
          }
          foreach ($removed_auth as $auth) {
            if (in_array($auth, $rest_config
              ->getAuthenticationProviders($request_method), TRUE)) {
              $configuration[$request_method]['supported_auth'] = array_diff($configuration[$request_method]['supported_auth'], $removed_auth);
            }
          }
          if (empty($configuration[$request_method]['supported_auth'])) {

            // Remove the key if there are no more authentication providers
            // supported by this request method.
            unset($configuration[$request_method]['supported_auth']);
          }
          if (empty($configuration[$request_method]['supported_formats'])) {

            // Remove the key if there are no more formats supported by this
            // request method.
            unset($configuration[$request_method]['supported_formats']);
          }
          if (empty($configuration[$request_method])) {

            // Remove the request method altogether if it no longer has any
            // supported authentication providers or formats.
            unset($configuration[$request_method]);
          }
        }
      }
      if ($configuration_before != $configuration && !empty($configuration)) {
        $rest_config
          ->set('configuration', $configuration);

        // Only mark the dependencies problems as fixed if there is any
        // configuration left.
        $changed = TRUE;
      }
    }

    // If the dependency problems are not marked as fixed at this point they
    // should be related to the resource plugin and the config entity should
    // be deleted.
    return $changed;
  }

  /**
   * Informs the entity that entities it depends on will be deleted.
   *
   * @param \Drupal\rest\RestResourceConfigInterface $rest_config
   *   The rest configuration.
   * @param array $dependencies
   *   An array of dependencies that will be deleted keyed by dependency type.
   *   Dependency types are, for example, entity, module and theme.
   *
   * @return bool
   *   TRUE if the entity has been changed as a result, FALSE if not.
   */
  protected function onDependencyRemovalForResourceGranularity(RestResourceConfigInterface $rest_config, array $dependencies) {
    $changed = FALSE;

    // Only module-related dependencies can be fixed. All other types of
    // dependencies cannot, because they were not generated based on supported
    // authentication providers or formats.
    if (isset($dependencies['module'])) {

      // Try to fix dependencies.
      $removed_auth = array_keys(array_intersect($this->authProviders, $dependencies['module']));
      $removed_formats = array_keys(array_intersect($this->formatProviders, $dependencies['module']));
      $configuration_before = $configuration = $rest_config
        ->get('configuration');
      if (!empty($removed_auth) || !empty($removed_formats)) {

        // All methods support the same formats and authentication providers, so
        // get those for whichever the first listed method is.
        $first_method = $rest_config
          ->getMethods()[0];

        // Try to fix dependency problems by removing affected
        // authentication providers and formats.
        foreach ($removed_formats as $format) {
          if (in_array($format, $rest_config
            ->getFormats($first_method), TRUE)) {
            $configuration['formats'] = array_diff($configuration['formats'], $removed_formats);
          }
        }
        foreach ($removed_auth as $auth) {
          if (in_array($auth, $rest_config
            ->getAuthenticationProviders($first_method), TRUE)) {
            $configuration['authentication'] = array_diff($configuration['authentication'], $removed_auth);
          }
        }
        if (empty($configuration['authentication'])) {

          // Remove the key if there are no more authentication providers
          // supported.
          unset($configuration['authentication']);
        }
        if (empty($configuration['formats'])) {

          // Remove the key if there are no more formats supported.
          unset($configuration['formats']);
        }
        if (empty($configuration['authentication']) || empty($configuration['formats'])) {

          // If there no longer are any supported authentication providers or
          // formats, this REST resource can no longer function, and so we
          // cannot fix this config entity to keep it working.
          $configuration = [];
        }
      }
      if ($configuration_before != $configuration && !empty($configuration)) {
        $rest_config
          ->set('configuration', $configuration);

        // Only mark the dependencies problems as fixed if there is any
        // configuration left.
        $changed = TRUE;
      }
    }

    // If the dependency problems are not marked as fixed at this point they
    // should be related to the resource plugin and the config entity should
    // be deleted.
    return $changed;
  }

}