Promise-state-machine-es6 NPM

Promise State Machine ES6

This is a rewritten version of promise-state-machine but with no dependencies; not bluebird - just native ES6, DOT data generation support for use with Graphvis or vis.js, to generate a visual representation of your state machine.

Installation

npm install promise-state-machine-es6 --save

Class PromiseStateMachine

Constructor(options)

state - May be any primitive type. options.initial - Initial state.
options.events - An Object where key denotes a transition.
options.events[transition].from - From state, may be an array of state.
options.events[transition].to - To state

Each key defined in options.events is defined as a method on the current instance. Use these methods to request a state transition. These methods returns a Promise that Resolves when transition succeded and Rejects when failed. To intercept a transition listen on the transition name, eg if options.events has "warn" transition we can intercept it by fsm.on('warn', (from, to, ...rest) => Promise.resolve()). This event would get called when fsm.warn(...rest).then() is called.

is(...states) : Bool

Check if instance is in any state. Argument may be one or many states or an array of states.

can(...events) : Bool

Check if instance can transition to a specific state. Argument may be one or many events or an array of events.

state getter : state

Get current state

toDOTsync(options) : String

Synchronously create DOT file data as a string.
options.replacer - Optional synchronous replacer function that takes a data object and returns a data object with all values stringified.

data.from - From state
data.to - To state
data.transition - Transition key

# Events

`[eventsKey]` (from, to, ...arguments)

A transition event for each key of options.events passed to the constructor may be emitted when calling any method as defined by options.events.

transition (transitionKey, from, to, ...arguments)

This event is emitted before transitionKey event is emitted, returning a Promise that rejects will abort the transition and eventsKey event will not be emitted.

Examples

Complete Example

const fsm = new PromiseStateMachine({
  initial: 'green',
  events: {
    warn: { from: 'green', to: 'yellow' },
    panic: { from: ['green', 'yellow'], to: 'red' },
    calm: { from: 'red', to: 'yellow' },
    clear: { from: ['yellow', 'red'], to: 'green' }
  }
});

fsm.on('warn', (from, to) => {
  return Promise.resolve('result 1');
});

fsm.on('warn', (from, to, transaction, somethingElse) => {
  return Promise.resolve('result 2');
});

fsm.on('transaction', (transition, from, to, ...rest) => {
    transition; // => 'warn'
});

fsm.warn(transaction, somethingElse).then(function(results) {
  // results: ['result 1', 'result 2']
}, function(error) {
  // could receive a StateTransitionError if trying to transition via an
  // inaccessible event.
});

fsm.is('green'); // => false
fsm.is('yellow'); // => true
fsm.state; // => 'yellow'
fsm.can('calm'); // => false
fsm.can('panic'); // => true

toDOTsync

const dotDataString = new PromiseStateMachine({
    events: {
        approve: { from: 'pending', to: 'approved' },
        reject: { from: ['pending', 'approved'], to: 'rejected' },
        pend: { from: ['approved', 'rejected'], to: 'pending' },
    }
}).toDOTsync();

Alt text

toDOTsync

const dotDataString = new PromiseStateMachine({
    events: {
        doWork: { from: ['Working', 'Starting'], to: 'Working' },
        handleError: { from: ['Working', 'Starting'], to: 'Error' },
        end: { from: ['Working', 'Starting'], to: 'End' }
    }
}).toDOTsync();

Alt text

Inheritance

class MyClass extends PromiseStateMachine {
    constructor(options) {    
        super(options);
    }
}

const fsm = new MyClass({
    initial: 'green',
    events: {
        warn: { from: 'green', to: 'yellow' },
        panic: { from: 'yellow', to: 'red' },
        calm: { from: 'red', to: 'yellow' },
        clear: { from: 'yellow', to: 'green' }
    }
});
fsm.is('green'); // => true
fsm.warn().then(() => {
  fsm.is('green'); // => false
});