interface SchedulableState : ContractState {
    /**
     * Indicate whether there is some activity to be performed at some future point in time with respect to this
     * [ContractState], what that activity is and at what point in time it should be initiated.
     * This can be used to implement deadlines for payment or processing of financial instruments according to a schedule.
     *
     * The state has no reference to it's own StateRef, so supply that for use as input to any FlowLogic constructed.
     *
     * @return null if there is no activity to schedule.
     */
    fun nextScheduledActivity(thisStateRef: StateRef, flowLogicRefFactory: FlowLogicRefFactory): ScheduledActivity?
}

class ExampleState(val initiator: Party,
                   val requestTime: Instant,
                   val delay: Long) : SchedulableState {
     override val contract: Contract get() = DUMMY_PROGRAM_ID
     override val participants: List<AbstractParty> get() = listOf(initiator)
     override fun nextScheduledActivity(thisStateRef: StateRef, flowLogicRefFactory: FlowLogicRefFactory): ScheduledActivity? {
         val responseTime = requestTime.plusSeconds(delay)
         val flowRef = flowLogicRefFactory.create(FlowToStart::class.java)
         return ScheduledActivity(flowRef, responseTime)
     }
 }

@InitiatingFlow
@SchedulableFlow
class FlowToStart : FlowLogic<Unit>() {
    @Suspendable
    override fun call() {
        // Do stuff.
    }
}