CommandBus.kt

import java.lang.reflect.ParameterizedType

interface Command
interface CommandHandler<C: Command> {
    fun invoke(command: C)
}

class CommandBus(val handlers: List<CommandHandler<out Command>>) {
    @PublishedApi
    internal val commandToCommandHandler: Map<String, CommandHandler<out Command>> =
        this.handlers.map { (it.javaClass.genericInterfaces[0] as ParameterizedType).actualTypeArguments[0].typeName to it }.toMap()

    inline fun <reified C: Command> invoke(command: C) {
        //TODO : Either if it does not exist
        val handler = this.commandToCommandHandler.get(command::class.simpleName)

        @Suppress("UNCHECKED_CAST")
        (handler as CommandHandler<C>).invoke(command)
    }
}

class SimpleCommand: Command
class SimpleCommandHandler: CommandHandler<SimpleCommand> {
    override fun invoke(command: SimpleCommand) {
        println("SIMPLE COMMAND")
    }
}

class AnotherCommand: Command
class OtherCommandHandler: CommandHandler<AnotherCommand> {
    override fun invoke(command: AnotherCommand) {
        println("OTHER COMMAND")
    }
}

fun main(vararg args: String) {
    val simpleCommandHandler: SimpleCommandHandler = SimpleCommandHandler()
    val otherCommandHandler: OtherCommandHandler = OtherCommandHandler()

    val bus = CommandBus(listOf(simpleCommandHandler, otherCommandHandler))

    val command = SimpleCommand()

    bus.invoke(command)
}