rx-interdependency-experiment

index.js

var Rx = require('rx');
var clone = require('lodash.clone');
var isequal = require('lodash.isequal');

var Config = new MutableSubject({a: null});
var Options = new MutableSubject({});

function MutableSubject(name, obj) {
  var behaviorSubject = new Rx.BehaviorSubject(obj);

  var mutableSubject = function (val, done) {
    if (arguments.length) {
      return setImmediate(function () {
        behaviorSubject.onNext(val);
        if (done) {
          done();
        }
      }, this);
    }

    return behaviorSubject.getValue();
  };
  mutableSubject._subject = behaviorSubject;
  return mutableSubject;
}

function changeConfig(key, value) {
  var newConfig = clone(Config());
  newConfig[key] = value;
  Config(newConfig);
}

function getOptions(config) {
  var options = {};
  for (var i in config) {
    var options;
    var firstChar = i.charAt(0);
    options[i] = [firstChar, firstChar + firstChar];
  }
  return options;
}

var uniqueConfig = Config._subject.distinctUntilChanged(null, isequal);

uniqueConfig
.subscribe(function (config) {
  // Whenever config changes, update options
  var newOptions = getOptions(config);
  Options(newOptions);
});

var uniqueOptions = Options._subject.distinctUntilChanged(null, isequal);

Rx.Observable.combineLatest(uniqueOptions, uniqueConfig)
.filter(function containsEmptyOptions(optionsAndConfig) {
  // Whenever options change, and it's unique, get latest from config,
  // check if there are any missing options
  var config = optionsAndConfig[1];
  var options = optionsAndConfig[0];

  for (var i in options) {
    if (!config[i]) {
      return true;
    }
  }

  return false;
})
.subscribe(function fillInDefaults(optionsAndConfig) {
  // If there are missing options, fill it up.
  var newConfig = clone(optionsAndConfig[1]);
  var options = optionsAndConfig[0];
  for (var i in options) {
    if (!newConfig[i]) {
      newConfig[i] = options[i][0];
    }
  }
  Config(newConfig);
});

function showState() {
  console.log(Config(), Options());
}

module.exports = {
  changeConfig: changeConfig,
  showState: showState
};

package.json

{
  "name": "rx-interdependency-experiment",
  "version": "0.0.0",
  "description": "",
  "main": "index.js",
  "dependencies": {
    "lodash.clone": "^3.0.3",
    "lodash.isequal": "^3.0.4",
    "rx": "^4.0.0"
  },
  "devDependencies": {},
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "",
  "license": "ISC"
}