channel/result.go

package channel

type Result[T any] struct {
	value *T
	err   error
}

func ResultOf[T any](value T, err error) Result[T] {
	if err != nil {
		return Result[T]{value: nil, err: err}
	}

	return Result[T]{value: &value, err: nil}
}

func WrapMapFunc[I, O any](f func(I) (O, error)) func(I) Result[O] {
	return func(i I) Result[O] { return ResultOf(f(i)) }
}

func WrapMapResultFunc[I, O any](f func(I) (O, error)) func(Result[I]) Result[O] {
	resFunc := WrapMapFunc(f)
	nilValue := *new(O)
	return func(r Result[I]) Result[O] {
		v, err := r.Get()
		if err != nil {
			return ResultOf(nilValue, err)
		}
		return resFunc(v)
	}
}

func (r Result[T]) Success() bool {
	return r.err == nil
}

func (r Result[T]) Fail() bool {
	return !r.Success()
}

func (r Result[T]) GetOrDefault(defaultValue T) T {
	if r.Fail() {
		return defaultValue
	}

	return *r.value
}

func (r Result[T]) Get() (T, error) {
	return *r.value, r.err
}

func (r Result[T]) GetSafe() T {
	if r.err != nil {
		panic(r.err)
	}
	return *r.value
}

func (r Result[T]) Err() error {
	return r.err
}

func FilterSuccess[T any](source <-chan Result[T]) <-chan T {
	succeeded := Filter(source, func(r Result[T]) bool { return r.Success() })

	return MapSuccessive(succeeded, func(r Result[T]) T {
		v, _ := r.Get()
		return v
	})
}

func FilterFail[T any](source <-chan Result[T]) <-chan T {
	failed := Filter(source, func(r Result[T]) bool { return r.Fail() })

	return MapSuccessive(failed, func(r Result[T]) T {
		v, _ := r.Get()
		return v
	})
}

func FilterResults[T any](source <-chan Result[T]) (succeeded <-chan T, failed <-chan error) {
	succ := make(chan T, cap(source))
	fail := make(chan error, cap(source))

	go func() {
		defer close(succ)
		defer close(fail)

		for r := range source {
			if r.Fail() {
				fail <- r.Err()
				continue
			}
			succ <- r.GetSafe()
		}
	}()

	return succ, fail
}