Promise State Machine ES6

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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

$3


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.

$3

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

$3

`javascript
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
`

$3


`javascript
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

$3

`javascript
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

$3

`javascript
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
});
``

TODO

- [ ] streamed version of toDOTsync

License

MIT

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