Finite state machine.

Install

npm i febs-fsm

write in Typescript.

Example

import {
  State, 
  StateEvent, 
  StateMechine
} from 'febs-fsm';

// Define Event1.
class Event1 extends StateEvent {
  constructor() {
    super('Event1');
  }
}

// Define State1.
class State1 extends State {
  constructor() {
    super('State1');
    this.addTransition('Event1', 'State2');
  }
  async onProcess( event:StateEvent, nextState:State ):Promise<{transition:boolean, ret?:any}> {
    return {transition: true};
  }
}

// Define State2.
class State2 extends State {
  constructor() {
    super('State2');
  }
  async onProcess( event:StateEvent, nextState:State ):Promise<{transition:boolean, ret?:any}> {
    return {transition: false};
  }
}


// Define mechine.
class Mechine extends StateMechine {
  constructor() {
    super('State1');  // init state identify.
    this.addState(new State1());
    this.addState(new State2());
  }
}

let mechine = new Mechine();
await mechine.initiate(); // initiate.
mechine.process_event(new Event1());  // process_event.

Standard FSM

standard: Store current state in mechine object. This applies to situations such as chat rooms.

import {
  State, 
  StateEvent, 
  StateMechine
} from 'febs-fsm';

Concurrent FSM

concurrent: Use the FSM concurrently. It isnot store current state in mechine object. Use context to pass the current state to FSM. Avoidance of repetition to set up FSM object.

import {
  State, 
  StateEvent, 
  StateMechine
} from 'febs-fsm/concurrent';

Identify

The Identify of state or event use string name:

// State1.
class State1 extends State {
  get identify():string { return 'State1'; }
}

State process flow

Execute curState.onProcess. It will do as follow, if function return {transition:true, ret?:any}.
Execute curState.onLeave
Change curState to nextState.
Execute nextState.onEnter

onProcess: {transition:boolean, ret:any}

transition: Indicates whether can to transition to nextState.
ret: Any value

onEnter: any

return a any value.

It will return the 'onEnter return value' or 'onProcess.ret', When call process_event.

brainpoint/febs-fsm