class DebugExtension

final class DebugExtension extends AbstractExtension {
  
  /**
   * The Symfony VarDumper class.
   *
   * Defined as a string because the Symfony VarDumper does not always exist.
   *
   * @var string
   */
  private const SYMFONY_VAR_DUMPER_CLASS = '\\Symfony\\Component\\VarDumper\\VarDumper';
  
  /**
   * {@inheritdoc}
   */
  public function getFunctions() : array {
    // Override Twig built in debugger when Symfony VarDumper is available to
    // improve developer experience.
    // @see \Twig\Extension\DebugExtension
    // @see \Symfony\Component\VarDumper\VarDumper
    if (class_exists(self::SYMFONY_VAR_DUMPER_CLASS)) {
      return [
        new TwigFunction('dump', [
          self::class,
          'dump',
        ], [
          'needs_context' => TRUE,
          'needs_environment' => TRUE,
          'is_variadic' => TRUE,
        ]),
      ];
    }
    return [];
  }
  
  /**
   * Dumps information about variables using Symfony VarDumper.
   *
   * @param \Twig\Environment $env
   *   The Twig environment.
   * @param array $context
   *   Variables from the Twig template.
   * @param array $variables
   *   (optional) Variable(s) to dump.
   */
  public static function dump(Environment $env, array $context, ...$variables) : void {
    if (!$env->isDebug()) {
      return;
    }
    if (class_exists(self::SYMFONY_VAR_DUMPER_CLASS)) {
      if (func_num_args() === 2) {
        call_user_func(self::SYMFONY_VAR_DUMPER_CLASS . '::dump', $context);
      }
      else {
        array_walk($variables, self::SYMFONY_VAR_DUMPER_CLASS . '::dump');
      }
    }
    else {
      throw new \LogicException('Could not dump the variable because symfony/var-dumper component is not installed.');
    }
  }

}