pre:

  class WorkflowHandler(private val workflows: Map<String, List<Rule>>) {
        private fun handleStandard(
            rule: Rule.Standard,
            sum: Long,
            rr: RatingRange,
        ): Ior<Long, RatingRange> {
            val (rrt, rrf) = rule.split(rr)
            val newSum: Long =
                sum +
                    when (val o = rule.output) {
                        RuleOutput.Accepted -> rrt.size()
                        is RuleOutput.NextRule -> crop(rrt, o.name)
                        else -> 0L
                    }
            return (newSum to rrf).bothIor()
        }

        private fun handleAuto(
            rule: Rule.Automatic,
            sum: Long,
            rr: RatingRange,
        ): Ior<Long, RatingRange> {
            return (
                sum +
                    when (val o = rule.output) {
                        RuleOutput.Accepted -> rr.size()
                        is RuleOutput.NextRule -> crop(rr, o.name)
                        else -> 0L
                    }
            ).leftIor()
        }

        fun crop(
            ratingRange: RatingRange = RatingRange(),
            wfName: String = "in",
        ): Long {
            return workflows.getValue(wfName)
                .fold(ratingRange.rightIor() as Ior<Long, RatingRange>) { ior, rule ->
                    ior.fold(
                        fa = { it.leftIor() },
                        fb = {
                            when (rule) {
                                is Rule.Standard -> handleStandard(rule, 0L, it)
                                is Rule.Automatic -> handleAuto(rule, 0L, it)
                            }
                        },
                        fab = { left, right ->
                            when (rule) {
                                is Rule.Standard -> handleStandard(rule, left, right)
                                is Rule.Automatic -> handleAuto(rule, left, right)
                            }
                        },
                    )
                }.leftOrNull() ?: 0L
        }
    }