Decomposed WireTransfer FSM definition

wire_transfer.go

func whenInitial(wt *fsm.FSM) fsm.StateFunction {
	return func(event *fsm.Event) *fsm.NextState {
		transfer, transferOk := event.Message.(*Transfer)
		if transferOk && event.Data == nil {
			transfer.source <- transfer.amount
			return wt.Goto(AwaitFromState).With(
				&WireTransferData{transfer.source, transfer.target, transfer.amount, wt},
			)
		}
		return wt.DefaultHandler()(event)
	}
}

func whenAwaitFrom(wt *fsm.FSM) fsm.StateFunction {
	return func(event *fsm.Event) *fsm.NextState {
		data, dataOk := event.Data.(*WireTransferData)
		if dataOk {
			switch event.Message {
			case Done:
				data.target <- data.amount
				return wt.Goto(AwaitToState)
			case Failed:
				go data.client.Send(Failed)
				return wt.Stay()
			}
		}
		return wt.DefaultHandler()(event)
	}
}

func whenAwaitTo(wt *fsm.FSM, transferred chan bool) fsm.StateFunction {
	return func(event *fsm.Event) *fsm.NextState {
		data, dataOk := event.Data.(*WireTransferData)
		if dataOk {
			switch event.Message {
			case Done:
				transferred <- true
				return wt.Stay()
			case Failed:
				go data.client.Stay()
			}
		}
		return wt.DefaultHandler()(event)
	}
}

func newWireTransfer(transferred chan bool) *fsm.FSM {
	wt := fsm.NewFSM()

	wt.StartWith(InitialState, nil)

	wt.When(InitialState)(whenInitial(wt))

	wt.When(AwaitFromState)(whenAwaitFrom(wt))

	wt.When(AwaitToState)(whenAwaitTo(wt, transferred))

	return wt
}