Coroutine Kotlin Example in PLP Essay

Stage.kt

import kotlinx.coroutines.*
import java.lang.RuntimeException
import kotlin.coroutines.CoroutineContext

class Enemy

fun addEnemy(enemy: Enemy){
    println("Added enemy!!")
}

object CoroutineTaskDispatcher : MainCoroutineDispatcher() {
    override val immediate: MainCoroutineDispatcher = this
    private val map = HashMap<CoroutineContext, Runnable>()

    fun tick(job: Job) {
        if(!job.isCompleted){
            map[job]!!.run()
        }
        if (job.isCancelled && map.contains(job)) {
            throw RuntimeException("CoroutineTask failed")
        }
    }

    fun remove(job: Job) {
        map.remove(job)
    }

    override fun dispatch(context: CoroutineContext, block: Runnable) {
        map[context.job] = block
    }
}

suspend fun wait(frame:Int) = repeat(frame) { yield() }
suspend fun task(){
    repeat(10){
        wait(120)
        val enemy=Enemy()
        addEnemy(enemy)
    }
}

var job:Job?=null
fun onTick(){
    if(job==null) {
        job=CoroutineScope(CoroutineTaskDispatcher).launch {
            task()
        }
    }

    CoroutineTaskDispatcher.tick(job!!)
}