Implementing actors in JavaScript.

actor.js

// Turns out this was not too difficult.
// By using the event loop as a global mail box ordering is even guaranteed for messages between only two actors.
// TODO would like to try and put one actor in a web worker to get some real parallism
// TODO would like to handle errors and have the concept of a deceased actor while a reference to an actor still exists. Probably involves creating an actor system like in Scala. Eurgh.

var actor = {
  send: function(message) {
    var self = this;
    console.log("sending to:", self);
    setTimeout(function(){
      self.receive(message);
    }, 0);
  },
  state: 0,
  receive: function(message){
    this.state += message;
    console.log(this.state);
  }
};


// console.log("hello");
// actor.send(1);
// actor.send(1);
// actor.send(1);

function End(){}

var end = new End();

function Actor(handler, state){
  this.handler = handler;
  this.state = state;
}

Actor.prototype.end = function(){
  return new End();
};

Actor.prototype.send = function(message){
  var self = this;
  setTimeout(function(){
    self.receive(message);
  });
  return self;
};

Actor.prototype.receive = function(message){
  reply = this.handler(this.state, message);
//   Could just end by throwing errors instead
  if (reply instanceof End) {
    console.log("ending");
    this.handler = function(){};
  } else {
    this.state = reply;
  }
};

function add(a, b){
  console.log(a);
  return a === 3 ? new End() : a + b;
}

var a = new Actor(add, 0);

a.send(1).send(1).send(1).send(1).send(1).send(1);

var shout = new Actor(function(state, message){
  console.log(message);
});

var forward = new Actor(function(target, message){
  target.send(message);
  return target;
}, shout); 

// forward.send("first");
// shout.send("second");

var ponger = new Actor(function(state, message){
  message.from.send(message.payload);
});

var pinger = new Actor(function(state, message){
  if (message.ping) {
    state.send({from: this, payload: message.payload});
  } else {
    console.log(message);
  }
}, ponger);


pinger.send({ping: true, payload: "huzzah"});