lets say I am using `Either`, and I have two param...

# arrow

[0xf1f1]

lets say I am using Either, and I have two params called due and standing - both params are charges to the customer and the code that generates both returns Either<Problem, Amount> -- What is the most effective way to map the generic problems to each param ? The Amount domain object returns a generic AmountProblem, but I need DueAmountProblem and StandingAmountProblem for proper validation.

[0xf1f1]

I am doing the below at the moment but it feels cumbersome:

[0xf1f1]

sealed interface BillProblem: Problem {
data object DueAmountLessThanZero: BillProblem
data object DueAmountIsNegative: BillProblem
data object StandingChargeAmountLessThanZero: BillProblem
data object StandingChargeAmountIsNegative: BillProblem
}

data class Bill(val due: Money, val standing: Money) {
companion object {

private fun createStandingAmount(
dto: Money
): EitherNel<Problem, Amount> =
Money.make(dto).mapLeft { problems ->
problems.map {
when (it) {
MoneyProblem.LessThanZero ->
BillProblem.StandingChargeAmountLessThanZero
MoneyProblem.IsNegative ->
BillProblem.StandingChargeAmountIsNegative
}
}
}

private fun createDueAmount(
dto: Money
): EitherNel<Problem, Amount> =
Money.make(dto).mapLeft { problems ->
problems.map {
when (it) {
MoneyProblem.LessThanZero ->
BillProblem.DueAmountLessThanZero
MoneyProblem.IsNegative ->
BillProblem.DueAmountIsNegative
}
}
}

fun create(
bill: dto
): EitherNel<Problem, Bill> = either {
Bill(
due = createDueAmount(dto.dueAmount).bind(),
standing = createStandingAmount(dto.standingAmount).bind()
)
}
}
}

[phldavies]

something like

private fun createAmount(dto: Money, lessThanZero: BillProblem, isNegative: BillProblem): EitherNel<BillProblem, Amount> =
    Money.make(dto).mapLeft { problems ->
        problems.map {
            when (it) {
                MoneyProblem.LessThanZero -> lessThanZero
                MoneyProblem.IsNegative -> isNegative
            }
        }
    }
    
fun create(
    bill: dto
): EitherNel<Problem, Bill> = either {
    Bill(
        due      = createAmount(dto.dueAmount, BillProblem.DueAmountLessThanZero, BillProblem.DueAmountIsNegative).bind(),
        standing = createStandingAmount(dto.standingAmount, BillProblem.StandingChargeAmountLessThanZero, BillProblem.StandingChargeAmountIsNegative).bind()
    )
}

[phldavies]

or have a data class LessThanZero(val amountType: AmountType): BillProblem etc