Functional decorator

FunctionalDecorator.scala

object Rebates {
  type RebatePolicy = (Product, Int, Money) => Money
}

object standardRebate extends ((Double, Int) => RebatePolicy) {

  def apply(rebate: Double, minimalQuantity: Int) = {
    (product, quantity, regularCost) => {
      val rebateRatio = BigDecimal(rebate / 100)
      if (quantity >= minimalQuantity)
        regularCost * rebateRatio
      else
        Money(0)
    }
  }
}

object vipRebate extends 
((Money, Money) => Option[RebatePolicy] => RebatePolicy) {

  override def apply(minimalThreshold: Money, rebateValue: Money) =
    (innerPolicy) => {
      (product, quantity, regularCost) => {
        val baseValue = innerPolicy.map(_(product, quantity, regularCost)).
        getOrElse(regularCost)
        if (baseValue > minimalThreshold)
          (baseValue - rebateValue)
        else baseValue
      }
    }
}

// somewhere in a rebate factory:
  
def createPolicy: RebatePolicy = {

    val vipPolicy = vipRebate(Money(1000), Money(100))
    val standard = standardRebate(10, 1)

    if (isVip)
      vipPolicy(Some(standard))
    else
      standard
  }