Decorator.kt

interface Component {
    fun operation()
}

class ConcreteComponent : Component {
    override fun operation() {
        // implementation
    }
}

abstract class Decorator(private val component: Component) : Component {
    override fun operation() {
        component.operation()
    }
}

class ConcreteDecoratorA(component: Component) : Decorator(component) {
    override fun operation() {
        super.operation()
        // additional behavior
    }
}

class ConcreteDecoratorB(component: Component) : Decorator(component) {
    override fun operation() {
        super.operation()
        // additional behavior
    }
}