is there an open source (free) Kotlin library that provides either a production ready Finite State Machine or a light weight rules engine implementation? could some one recommend one please 😄

We've used https://github.com/Tinder/StateMachine in the past, is that the kind of thing you had in mind?

There's also https://github.com/open-jumpco/kfsm but I would also prefer Kstatemachine instead which is IMHO more solid and provides a more approachable API.