Chaining Validations

gistfile1.scala

class ChainedValidation[E,A](val x : A, val validationResult: ValidationNel[E,A]) {
  
  def andThen(f: A => ValidationNel[E, A])(implicit s1: Semigroup[E]) : ChainedValidation[E,A] = {
    // calculate new validation
    val newResult = f(x) 
 
    validationResult match {
      // (success & newResult) =>
      case Success(_) => 
      	newResult match {
      	  // (success & success => success
      	  case Success(a) => new ChainedValidation[E,A](x, a.successNel[E])
      	  // (success & failure => failure
      	  case Failure(e) => new ChainedValidation(x, e.fail[A])
      	}
      // (failure & newResult =>)
      case Failure(e) =>
        newResult match {
          // (failure & success) => failure
          case Success(a) => new ChainedValidation(x, validationResult)
          // (failure & failure) => failure + failure
          case Failure(eNew) => 
            new ChainedValidation(x, (e append eNew).failure[A])
      }
    } 
  } 
}

object ChainedValidation {
  def apply[E,A](x: A, f: A => ValidationNel[E, A]) = new ChainedValidation[E,A](x, f(x))
}