validated.scala

object Validation extends App {

  object FailFast {
    def validationEven(i: Int): Either[String, Int]  = if (i % 2 == 0) Right(i) else Left("Odd")
    def validationLT100(i: Int): Either[String, Int] = if (i < 100) Right(i) else Left("GT 100")
    def validationGT0(i: Int): Either[String, Int]   = if (i > 0) Right(i) else Left("LT 0")

    def validation(i: Int): Either[String, Int] =
      for {
        _   <- validationEven(i)
        _   <- validationLT100(i)
        res <- validationGT0(i)
      } yield res
  }

  object FailureAccumulation {
    def validationEven(i: Int): Validated[List[String], Int]  = if (i % 2 == 0) Valid(i) else Invalid(List("Odd"))
    def validationLT100(i: Int): Validated[List[String], Int] = if (i < 100) Valid(i) else Invalid(List("GT 100"))
    def validationGT0(i: Int): Validated[List[String], Int]   = if (i > 0) Valid(i) else Invalid(List("LT 0"))

    def validation(i: Int): Validated[List[String], Int] =
      (validationEven(i), validationLT100(i), validationGT0(i)).mapN { case (_, _, res) => res }
  }

  val ok      = 50
  val koOdd   = 51
  val koGT100 = 101
  val koLT0   = -1

  println(FailFast.validation(ok))
  println(FailFast.validation(koOdd))
  println(FailFast.validation(koGT100))
  println(FailFast.validation(koLT0))

  println(FailureAccumulation.validation(ok))
  println(FailureAccumulation.validation(koOdd))
  println(FailureAccumulation.validation(koGT100))
  println(FailureAccumulation.validation(koLT0))
}