FSM DSL in Kotlin tomoya0x00 Kotlin Developers Meetup

About me tomoya0x00 Twitter, GitHub, Qiita Android, Embedded system, BLE/BT, iOS DeNA Co., Ltd. Automotive Business Unit.

Everyone

You want to make DSL by yourself?

I want to FSM DSL in Kotlin FSM is nite state machine.

Why FSM? Avoid confusion caused by multiple ag management Easy to test

And, I want to support composite states

Example

Simple smart lock for bike sharing

I am developing a Proof-of-Concept

DSL Example val sm = stateMachine(initial = MyState.NotLoaned) { state(MyState.NotLoaned) { edge(MyEvent.PressRental, next = MyState.Lock) } state(MyState.OnLoan, entry = { println("turnOnRentalLed") }, exit = { println("turnOffRentalLed") }) { state(MyState.Lock) { edge(MyEvent.PressReturn, next = MyState.NotLoaned) edge(MyEvent.PressUnLock, next = MyState.UnLock) } state(MyState.UnLock) { edge(MyEvent.PressLock, next = MyState.Lock) } } }

Let's run! val next = sm.dispatch(MyEvent.PressRental) assert(next).isEqualTo(MyState.Lock) result: turnOnRentalLed next == MyState.Lock

Internal

Generate the tree of states DSL Tree of states

DSL internal fun stateMachine( initial: BaseState, init: StateMachine.() -> Unit ): StateMachine = StateMachine(initial = initial) .apply(init)

Problem

Search processing is executed for each dispatch

When press return in Lock state Find route to NotLoaned state from Lock state

When press return in Lock state Find route to NotLoaned state from Lock state

When press return in Lock state Find route to NotLoaned state from Lock state

When press return in Lock state Find route to NotLoaned state from Lock state

When press return in Lock state Find route to NotLoaned state from Lock state

When press return in Lock state Execute entry/exit on route

Solution

StateMachine.Builder fun stateMachine( initial: BaseState, init: StateMachine.Builder.() -> Unit ): StateMachine = StateMachine.Builder(initial = initial) .apply(init).build()

Generate transition map in build() state event actions next NotLoaned PressRental [OnLoan.entry] Lock Lock PressReturn [OnLoan.exit] NotLoaned Lock PressUnLock [] UnLock UnLock PressLock [] Lock

But, not implemented yet... to be available soon!

Any Idea? Tree search algorithm when creating transition map, if you have any good idea, please let me know!

Waiting for your suggestions︕ https://github.com/tomoya0x00/fsm-dsl- kotlin-poc

Thank you!