kubukoz

def time() = System.currentTimeMillis()

val t1 = time()
val x = calculateSomething(args)
val t2 = time()
println(t2 - t1) //print the time it took for `x` to be computed

kubukoz

def time(): Future[Long] = Future { System.currentTimeMillis() }

for {
  t1 <- time()
  x = calculateSomething(args)
  t2 <- time()
} println(t2 - t1)

kubukoz

val time: Future[Long] = Future { System.currentTimeMillis() }

for {
  t1 <- time
  x = calculateSomething(args)
  t2 <- time
} println(t2 - t1)

kubukoz

val time: Task[Long] = Task { System.currentTimeMillis() }

for {
  t1 <- time
  x = calculateSomething(args)
  t2 <- time
} println(t2 - t1)

kubukoz

class Calc[F[_] : Sync] {
  def calculateSomething(args: List[String]): Int = ???
  
  def measureCalculation(args: List[String]): F[(Int, Long)] = {
    val time: F[Long] = Sync[F].delay { System.currentTimeMillis() }

    for {
      t1 <- time
      x = calculateSomething(args)
      t2 <- time

kubukoz

POST /views HTTP/1.1
Authorization: Bearer eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiJzY2FsYS1sYW5nLm9yZyIsImlhdCI6MTUxNjIzOTAyMn0.luv48L_lo4OkyGQIKiKN7nFK2Wypr1Hd2lwxTMPybUU

{
  displayed_at: "2018-05-16T09:00.000+01:00",
  path: "/articles/scala-3-delayed.html?source=twitter&tracking_id=6d9386c589f1e"
}

kubukoz

val viewService: HttpService[F] = HttpService {
  case req @ (POST -> Root / "views") =>
    for {
      viewed   <- req.decodeJson[PageViewed]
      ip       =  extractClientIp(req)
      result   <- pageViewService.checkAndSave(viewed, ip)
      response <- validatedToJson(result, successResponse = Created)
    } yield response
}

kubukoz

def checkAndSave(event: PageViewed,
                 hostname: String,
                 clientIp: Option[String]): F[ValidatedNel[PVError, Unit]]

kubukoz

sealed trait PVError extends Product with Serializable

object PVError {
  case object NoIp             extends PVError
  case object AlreadyTracked   extends PVError
  case object PageNotFound     extends PVError
  case object InvalidTimestamp extends PVError

  //helper functions to upcast easily
  val noIp: PVError             = NoIp

kubukoz

def checkAndSave(event: PageViewed,
                 hostname: String,
                 clientIp: Option[String]): F[ValidatedNel[PVError, Unit]] = {
  val normalizedPath = normalize(event.path)

  val uuidF: F[UUID] = Sync[F].delay { UUID.randomUUID() }
  val currentTimeF: F[OffsetDateTime] = getCurrentTimeF
  
  val ipValidationF: F[ValidatedNel[PVError, String]] =
    clientIp