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

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

kubukoz

val ipValidationF: F[ValidatedNel[PVError, String]] =
  clientIp
    .toValidNel(PVError.noIp)
    .traverse(checkIp(_, hostname, normalizedPath))
    .map(_.andThen(identity)

kubukoz

val pathValidationF: F[ValidatedNel[PVError, String]] =
  pageExists(hostname, normalizedPath).map(
    Validated.condNel(_, normalizedPath, PVError.pageNotFound))

kubukoz

(uuidF, currentTimeF, ipValidationF, pathValidationF).traverseN {
  (uuid, currentTime, ipValidation, pathValidation) => ...
}

kubukoz

val timestampV: ValidatedNel[PVError, OffsetDateTime] = event
  .displayedAt
  .valid
  .ensure(PVError.invalidTimestamp)(_.isBefore(currentTime))
  .toValidatedNel

(
  uuid.valid,
  pathValidation,
  timestampV,