ratelimit.scala

import java.time.LocalDateTime
import java.util.{Deque, LinkedList}
import scala.concurrent.{Future, Promise}
import scala.concurrent.duration._

class ApiService[T](limit: Long, timeFrame: FiniteDuration) {

  case class RequestQueueItem(f: () => Future[T], p: Promise[T])

  private var requestQueue: Deque[RequestQueueItem] = new LinkedList[RequestQueueItem]()
  private var requestCount: Long = 0
  private var windowStopTime: LocalDateTime = LocalDateTime.now()

  def request(f: () => Future[T]): Future[T] = this.synchronized {
    val p = Promise[T]()
    requestQueue.offerLast(RequestQueueItem(f, p))
    tryRequest()
    p.future
  }
  
  private def tryRequest(): Unit = this.synchronized {
    if (hasCapacity()) {
      makeRequest()
    }
  }

}