Scala MapN with conditions - scala

Question

Hi I have the following Scala code with cats library
results = patrons.map(p => {
(verifyCardId(p.cardId), verifyAddress(p.address)).map2(
(maybeValidCard, maybeValidAddress) => {
val result = for {
idCheck <- maybeValidCard
addressCheck <- maybeValidAddress
} yield CheckResult(p.name, idCheck, addressCheck)
}
})
where verifyCardId and verifyAddress is an external API call returning a Future which are somehow very expensive and time consuming.
The question is how do I do the following:
If one of the patron does not have a card, the code should be able to skip checking the card must still check patron's address
If the patron has both then, the code should check the card and the address
How can I improve the existing code? Thanks heaps
Edit:
Add more information about the preference to skip one of the expensive API calls

Answer 1

If result of address verification doesn't depend on result of card verification then untie them (flatMap binds monads).
Model CheckResult should be adjusted to case of missing card.
extended sample
case class Patron(name: String, cardId: String, address: String)
case class CheckResult(name: String, idCheck: Option[Boolean], addressCheck: Boolean)
def verifyCardId(cardId: String) = Future{
Thread.sleep(5000)
Some(true)
}
def verifyAddress(address: String) = Future{
Thread.sleep(5000)
Some(true)
}
val patrons = List(Patron("p_name", "1234", "Somewhere St. 42"))
val start = LocalDateTime.now()
val results = patrons.map(p => {
(verifyCardId(p.cardId), verifyAddress(p.address)).map2(
(maybeValidCard, maybeValidAddress) => {
for {
addressCheck <- maybeValidAddress
} yield CheckResult(p.name, maybeValidCard, addressCheck)
})
})
val headResult = Await.result(results.head, Duration.Inf)
val end = LocalDateTime.now()
val duration = ChronoUnit.SECONDS.between(start, end)
short output
patrons: List[Patron] = List(Patron(p_name,1234,Somewhere St. 42))
headResult: Option[CheckResult] = Some(CheckResult(p_name,Some(true),true))
duration: Long = 5