ideas around a fake mini job queue

JobQueueRx.kt

package com.example.android.lib.rx

import io.reactivex.Observable
import java.util.concurrent.ConcurrentLinkedDeque
import java.util.concurrent.TimeUnit

class JobExample {

    val queue = ConcurrentLinkedDeque<Item>()

    fun add(item: Item): Observable<Item>? {

        queue.addLast(item)
        //queue.removeIf { it.key == item.key }  //something like this logic to cancel waiting jobs of the same 'key'

        return Observable
            .fromCallable {
                val next = queue.pollFirst()
                
                next?.let { //fake network call
                    println("making fake network call for ${next.key}  queue size ${queue.size}")
                    Thread.sleep(2000)
                }
                item   //end fake network call
            }
            .repeatWhen { repeater ->
                if (queue.isEmpty()) {
                    Observable.empty<Item>()
                } else {
                    println("delay...queue size: ${queue.size}")
                    repeater.concatMap { Observable.timer(150, TimeUnit.MILLISECONDS) }
                }
            }
    }
}

data class Item(val key: String, val value: Boolean)


/////// test

    @Test
    fun jobtest() {

        val jobex = JobExample()

        val list = mutableListOf<Item>()

        for (i in 0..10) {
            list.add(Item("key $i", true))
        }

        
        //simulate being clogged up!
        val preloadedKeys = mutableListOf<Item>()

        for (i in 0..10) {
            preloadedKeys.add(Item("preloaded key $i", true))
        }
        
        jobex.queue.addAll(preloadedKeys)

        list.forEach {
            jobex.add(it)?.subscribe()
        }


        println("done")
    }