requestLimiter.kt

package com.example.android.gdgfinder.libs

import kotlinx.coroutines.CompletableDeferred
import kotlinx.coroutines.CoroutineScope
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.channels.Channel
import kotlinx.coroutines.launch

class RequestLimiter<R>(scope: CoroutineScope) {
    val requestChannel = Channel<Pair<suspend () -> R, CompletableDeferred<R>>>()

    init {
        scope.launch {
            // don't know thread we're running on?? -- does it matter?
            for ((request, resultDeferred) in requestChannel) {
                try {
                    resultDeferred.complete(request())
                } catch (exception: Throwable) {
                    resultDeferred.completeExceptionally(exception)
                }

            }
        }
    }

    suspend fun doRequest(block: suspend () -> R): R {
        val result = CompletableDeferred<R>()
        requestChannel.send(block to result)
        return result.await()
    }
}

fun <R> CoroutineScope.singleRequestLimiter() = RequestLimiter<R>(this)

val RepositoryScope = CoroutineScope(Dispatchers.Main)

// usage
val requestLimiter = RepositoryScope.singleRequestLimiter<Int>()

suspend fun useIt() = requestLimiter.doRequest {
    1 // for very async values of 1
}