decorator.kt

abstract class Beverage {
    open val description: String = "Unknown Beverage"
    abstract val cost: Double
}

abstract class CondimentDecorator : Beverage() {
    abstract override val description: String
}

class Espresso: Beverage() {
    override val description = "Espresso"
    override val cost: Double = 1.99
}

class HouseBlend: Beverage() {
    override val description = "House Blend"
    override val cost: Double = .89
}

class Mocha(beverage: Beverage): CondimentDecorator() {
    override val cost: Double = beverage.cost + .20
    override val description: String = beverage.description + ", Mocha"
}

class Milk(beverage: Beverage): CondimentDecorator() {
    override val cost: Double = beverage.cost + .30
    override val description: String = beverage.description + ", Milk"
}

fun main() {
    val espresso = Espresso()
    println(espresso.description + " " + espresso.cost)

    val espressoWithMilk: Beverage = Milk(Milk(beverage = HouseBlend()))
    println(espressoWithMilk.description + " " + espressoWithMilk.cost)
}