Custom Either

custom_either.dart

import 'failure.dart';

class NoParams {
  const NoParams._();
}

const noParams = NoParams._();

class NoResponse {
  const NoResponse._();
}

const noResponse = NoResponse._();

abstract class CustomEither<TFailure, TSuccess> {
  final TFailure? _failure;
  final TSuccess? _success;
  CustomEither({TFailure? failure, TSuccess? success})
      : _failure = failure,
        _success = success,
        assert(failure != null || success != null);

  T fold<T>({T Function(TFailure)? onFailure, T Function(TSuccess)? onSuccess}) {
    if (_failure != null && onFailure != null) return onFailure(_failure!);
    if (_success != null && onSuccess != null) return onSuccess(_success!);
    throw CustomEitherNotDefinedFailure();
  }

  T? foldSuccess<T>(T Function(TSuccess)? onSuccess) {
    return fold(onFailure: (failure) => null, onSuccess: onSuccess);
  }

  T? foldFailure<T>(T Function(TFailure)? onFailure) {
    return fold(onSuccess: (value) => null, onFailure: onFailure);
  }

  static SuccessCustomEither<TFailure, TSuccess> success<TFailure, TSuccess>(TSuccess value) {
    return SuccessCustomEither<TFailure, TSuccess>(value);
  }

  static FailureCustomEither<TFailure, TSuccess> failure<TFailure, TSuccess>(TFailure value) {
    return FailureCustomEither<TFailure, TSuccess>(value);
  }

  bool get isSuccess => _success != null;
  bool get isFailure => _failure != null;

  TSuccess? operator |(TSuccess? newFailureCustomEither) => fold(onFailure: (_) => newFailureCustomEither, onSuccess: (value) => value);
}

class SuccessCustomEither<TFailure, TSuccess> extends CustomEither<TFailure, TSuccess> {
  SuccessCustomEither(TSuccess value) : super(success: value);
}

class FailureCustomEither<TFailure, TSuccess> extends CustomEither<TFailure, TSuccess> {
  FailureCustomEither(TFailure value) : super(failure: value);
}

class CustomEitherNotDefinedFailure extends Failure {
  CustomEitherNotDefinedFailure()
      : super(code: 'failure-or-success-not-defined-in-custom-either', message: 'Invalid CustomEither. Failure or Success not defined');
}

failure.dart

abstract class Failure {
  final String code;
  final String message;
  final Object? exception;
  final StackTrace? stacktrace;
  const Failure({required this.code, required this.message, this.exception, this.stacktrace});
}

class InternalFailure extends Failure {
  const InternalFailure({Object? exception, StackTrace? stackTrace, String? message})
      : super(
          code: 'internal-failure',
          message: message ??
              'Ocorreu um erro interno, tente novamente. Se o problema persistir, entre em contato com o administrador do sistema.',
          exception: exception,
          stacktrace: stackTrace,
        );
}