Actor Model in JS

> Exploring the potential benefits of implementing APIs in the style of the Actor Model,
even in single-threaded programming environments such as Javascript.

TODO

$3

- [x] createSystem()
- [x] system.actorOf(IActorFactory) -> ActorRef

$3

- [x] actor.tell() - fire & forget message
- [x] actor.ask() - ask & await async response from an actor
- [x] actor.stop() - send a message instructing an actor to terminate

$3

- [x] context.stop(IActorRef) - allow an actor to be stopped via a ref
- [x] context.gracefulStop(IActorRef) - allow an actor to be stopped via a ref with confirmation (for sequencing etc)
- [x] context.actorOf(IActorFactory) - allow an actor to create more actors
- [x] context.parent - allow an actor to access it's parent (in order to send it messages)
- [x] context.self - allow an actor to access it's own ref (in order to send it's self messages)
- [ ] context.become(newHandler) - designate a new handler for future messages http://doc.akka.io/docs/akka/current/scala/actors.html#Graceful_Stop
- [x] context.actorSelection(lookup: string) - allow actor lookups via paths, such as /system /deadletter etc

$3

- [x] receive(payload, message, sender)
- [x] sender.reply() for replying directly to a message
- [x] mappedMethods define 1 function per message name
- [x] handle cancellation of pending message should a new one override it
- [x] pass state into mapped methods for encapsulated state management
- [x] sender - allow every message access to an ActorRef that allow communication with the sender

``js
receive (payload message sender)
switch payload
case 'ping' sender.reply 'pong'
default sender.reply 'missing'

// callsite
actor.ask 'ping'
|> resp console.log 'resp:' + resp
`



$3

- actorOf(...)
- [x] path is reserved
- [ ] uuid is assigned
- [x] actor instance is created
- [x] preStart is called on instance

- Incarnation (restarting)
- [x] preRestart called on old instance
- [x] new instance replaces old
- [x] postRestart called on new instance

- Stop, context.stop() or PoisonPill
- [x] postStop is called on instance
- [x] actor is removed from the internal system register
- [ ] Terminated is sent to watchers
- [x] path is free to be used again

- graceful stop http://doc.akka.io/docs/akka/current/scala/actors.html#Graceful_Stop
- [ ] become() - designate a new handler for future messages



$3

- [x] actorOf() only ever creates a new actor, and it creates it as a direct child of the context
on which this method is invoked (which may be any actor or actor system).
- [ ] /deadletters all messages sent to stopped or non-existing actors are re-routed here
- [x] /system` is the guardian actor for all system-created top-level actors, e.g. logging
listeners or actors automatically deployed by configuration at the start of the actor system.