A compilation of various promise generator controllers

async.js

// http://pag.forbeslindesay.co.uk/#/22
//
function async(makeGenerator){
  return function (){
    var generator = makeGenerator.apply(this, arguments)
    
    function handle(result){ // { done: [Boolean], value: [Object] }
      if (result.done) return result.value
      
      return result.value.then(function (res){
        return handle(generator.next(res))
      }, function (err){
        return handle(generator.throw(err))
      })
    }
    
    return handle(generator.next())
  }
}

var readJSON = async(function *(filename){
  return JSON.parse(yield readFile(filename, 'utf8'))
})

function readFile(filename, enc){
  return new Promise(function (fulfill, reject){
    fs.readFile(filename, enc, function (err, res){
      if (err) reject(err)
      else fullfill(res)
    })
  })
}

var get = async(function *(){
  var left = yield readJSON('left.json')
  var right = yield readJSON('right.json')
  return { left: left, right: right }
})

run.js

// https://gist.github.com/creationix/5761021
//
function run(generator) {
  var iterator = generator(resume);
  var data = null, yielded = false;
  
  iterator.next();
  yielded = true;
  check();
  
  function check() {
    while (data && yielded) {
      var err = data[0], item = data[1];
      data = null;
      yielded = false;
      if (err) return iterator.throw(err);
      iterator.send(item);
      yielded = true;
    }
  }
  
  function resume() {
    data = arguments;
    check();
  }
}

run(function*(resume) {
  console.log("Hello");
  yield setTimeout(resume, 1000);
  console.log("World");
});

spawn.js

// http://blogs.atlassian.com/2013/11/harmony-generators-and-promises-for-node-js-async-fun-and-profit/
//
var Q = require("q");
var ourSpawn = function(generatorFn) {
    var gen = generatorFn();
    // This method will get called over and over to keep pumping fulfilled
    // promise values back into the generator.
    var pumpGenerator = function(val) {
        var ret = gen.next(val);
        if(ret.done) {
            // Generator has completed. We're done here.
            return;
        }
        // Calling Q like this just wraps whatever the generator gave us back
        // in a promise, if it wasn't already a promise.
        var result = Q(ret.value);
        result.then(function(val) {
            // The promise that was yielded to us has completed. Pass it back
            // into the generator and get ready for another round of fun.
            pumpGenerator(val);
        });
    };
    pumpGenerator();
};