import java.util.*
import kotlin.reflect.KClass

object Events {

    private val map = HashMap<Class<*>, Set<EventHandler<*>>>(2048)

    fun <T> EventHandler(handler: (T) -> Unit): EventHandler<T> = object : EventHandler<T> {
        override fun handle(event: T) = handler(event)
    }

    fun <T : Any> handler(eventType: KClass<T>, handler: (T) -> Unit) = handlerJ(eventType.java, handler)

    private fun <T : Any> handlerJ(eventType: Class<T>, handler: (T) -> Unit) =
            handlers(eventType).add(EventHandler(handler))

    fun post(event: Any) = handlers(event.javaClass).forEach { it.handle(event) }

    operator fun plus(event: Any) = post(event)

    private fun <T> handlers(eventType: Class<T>): HashSet<EventHandler<T>> {
        var set = map[eventType]
        if (set == null) {
            set = HashSet<EventHandler<*>>()
            map.put(eventType, set)
        }
        return set as HashSet<EventHandler<T>>
    }

}