An object-oriented birthday card

Birthday.kt

import java.util.*

object Birthday {

	class BirthdayDependencyInjector {
		fun injectDependencyIntoTheFactory(dataProvider: GreetingCardDataProvider<Date>) : BirthdayCardProvider {
			return BirthdayCardProvider(dataProvider)
		}
	}

	abstract class AbstractBaseGreetingCardProviderFactory<R, out T:AbstractBaseGreetingCardProvider> {
		abstract fun getInstance(dataProvider: GreetingCardDataProvider<R>) : T
	}

	abstract class AbstractBaseGreetingCardProvider {
		abstract fun provideCard(name: String, msg: String, listener: GreetingCardMessageListener)
	}

	interface GreetingCardDataProvider<T> {
		fun getGreetingCardData(key: String) : T
	}

	interface GreetingCardMessageListener {
		fun receiveCardMessage(name: String, msg: String, date: Date)
	}

	class BirthdayCardDataProvider(val bday: Date) : GreetingCardDataProvider<Date> {
		override fun getGreetingCardData(key: String) : Date {
			return when (key) {
				"today" -> Date()
				"birthday" -> bday
				else -> Date()
			}
		}
	}

	class BirthdayCardProviderFactory : AbstractBaseGreetingCardProviderFactory<Date,BirthdayCardProvider>() {
		override fun getInstance(dataProvider: GreetingCardDataProvider<Date>) : BirthdayCardProvider {
			return BirthdayDependencyInjector().injectDependencyIntoTheFactory(dataProvider)
		}
	}

	class BirthdayCardProvider(val dataProvider: GreetingCardDataProvider<Date>) : AbstractBaseGreetingCardProvider() {
		override fun provideCard(name: String, msg: String, listener: GreetingCardMessageListener) {
			listener.receiveCardMessage(name, msg, dataProvider.getGreetingCardData("birthday"))
		}
	}

	class BirthdayCardMessageListener : GreetingCardMessageListener {
		override fun receiveCardMessage(name: String, msg: String, date: Date) {
			println("Happy Birthday, $name! Your birthday is $date")
			if (msg.isNotEmpty()) {
				println("I have an additional message for you:")
				println(msg)
			}
		}
	}

	@JvmStatic
	fun main(args: Array<String>) {
		BirthdayCardProviderFactory()
			.getInstance(BirthdayCardDataProvider(Date()))
			.provideCard("James", "May all your code run smoothly", BirthdayCardMessageListener())
	}

}