engine.js

import {Observable} from 'rx';

const INTERVAL = 1000 / 10;
const ticker = Observable.interval(INTERVAL);

import notifySystem from './systems/notify';
import locationSystem from './systems/location';
import arSceneSystem from './systems/ar-scene';
import userStatsSystem from './systems/user-stats';
import reactViewSystem from './systems/react-view';

const systems = [
  locationSystem,
  arSceneSystem,
  userStatsSystem,
  notifySystem,
  reactViewSystem
];

function runSystems (nextState, system) { return system(nextState); }
import userInputSystem from './systems/user-input';

function engineReducer(state) {
  const currentGame = state.get('currentGame');
  if (!currentGame) return state;
  const hasEntities = currentGame.has('entities');
  if (!hasEntities) return state;

  return systems.reduce(runSystems, state);
}

export default function engine() {
  console.log('Engine initialised');
  return ticker
            .map( () => engineReducer )
            .merge( userInputSystem() );
}