BusinessResult.scala

/**
 * Algebraic Data Type (ADT) for results that the business layers return to controllers.
 * It has two cases:
 * <ul>
 * <li> OKResult wrapping a value
 * <li> FailedResult containing a discriminator value and a list of error messages.
 * <ul>
 *  Author: https://github.com/kenbot
 */
sealed trait BusinessResult[+A] {
  def ok: Boolean

  def map[B](f: A => B): BusinessResult[B]

  def flatMap[B](f: A => BusinessResult[B]): BusinessResult[B]

  def getOrElse[B >: A](other: B): B

  def failedAs(errorCode: ErrorCode): Boolean
}

case class OKResult[+A](result: A) extends BusinessResult[A] {
  def ok: Boolean = true

  def map[B](f: A => B): BusinessResult[B] = OKResult(f(result))

  def flatMap[B](f: A => BusinessResult[B]): BusinessResult[B] = f(result)

  def getOrElse[B >: A](other: B): B = result

  def failedAs(errorCode: ErrorCode): Boolean = false
}

case class FailedResult(errorCode: ErrorCode, messages: String*) extends BusinessResult[Nothing] {

  def ok: Boolean = false

  def map[B](f: Nothing => B): BusinessResult[B] = this

  def flatMap[B](f: Nothing => BusinessResult[B]): BusinessResult[B] = this

  def getOrElse[B](other: B): B = other

  def failedAs(code: ErrorCode): Boolean = (errorCode == code)
}