snake.js

// Streams

/*
const ticker$ = Rx.Observable
  .interval(tickerInterval, Rx.Scheduler.requestAnimationFrame)
  .map(() => ({ time: Date.now(), delta: null }))
  .scan((previous, current) => ({
    time: current.time,
    delta: (current.time - previous.time) / 1000,
  }));
*/

const ticker$ = Rx.Observable
  .generate(0, x => true, x => x + 1, x => x, Rx.Scheduler.animationFrame)
  .scan(
    previous => {
      const time = Date.now();
      return {
        time: time,
        delta: (time - previous.time) / 1000,
      };
    },
    { time: Date.now(), delta: 0 }
  );

const input$ = Rx.Observable
  .fromEvent(document, 'keydown')
  .flatMap(
    event =>
      R.contains(event.keyCode, Object.keys(keyMap).map(n => parseInt(n)))
        ? [keyMap[event.keyCode]]
        : []
  );

const snake$ = ticker$.withLatestFrom(input$).scan((pos, [ticker, dir]) => {
  return pos.add(dir.multiplyScalar(snakeSpeed)).mod(boardSize);
}, snakeInitialPos);

const game = Rx.Observable.combineLatest(ticker$, snake$);

// go time
init();
game.subscribe(([ticker, position]) => draw(ticker, position));