elm-core-sources-1.0.0: src/Native/Time.js

Elm.Native.Time = {};
Elm.Native.Time.make = function(elm) {

  elm.Native = elm.Native || {};
  elm.Native.Time = elm.Native.Time || {};
  if (elm.Native.Time.values) return elm.Native.Time.values;

  var Signal = Elm.Signal.make(elm);
  var NS = Elm.Native.Signal.make(elm);
  var Maybe = Elm.Maybe.make(elm);
  var Utils = Elm.Native.Utils.make(elm);

  function fpsWhen(desiredFPS, isOn) {
    var msPerFrame = 1000 / desiredFPS;
    var prev = elm.timer.now(), curr = prev, diff = 0, wasOn = true;
    var ticker = NS.input(diff);
    function tick(zero) {
      return function() {
        curr = elm.timer.now();
        diff = zero ? 0 : curr - prev;
        if (prev > curr) {
          diff = 0;
        }
        prev = curr;
        elm.notify(ticker.id, diff);
      };
    }
    var timeoutID = 0;
    function f(isOn, t) {
      if (isOn) {
        timeoutID = elm.setTimeout(tick(!wasOn && isOn), msPerFrame);
      } else if (wasOn) {
        clearTimeout(timeoutID);
      }
      wasOn = isOn;
      return t;
    }
    return A3( Signal.map2, F2(f), isOn, ticker );
  }

  function every(t) {
    var clock = NS.input(elm.timer.now());
    function tellTime() {
        elm.notify(clock.id, elm.timer.now());
    }
    setInterval(tellTime, t);
    return clock;
  }

  function read(s) {
      var t = Date.parse(s);
      return isNaN(t) ? Maybe.Nothing : Maybe.Just(t);
  }
  return elm.Native.Time.values = {
      fpsWhen : F2(fpsWhen),
      fps : function(t) { return fpsWhen(t, Signal.constant(true)); },
      every : every,
      delay : NS.delay,
      timestamp : NS.timestamp,
      toDate : function(t) { return new window.Date(t); },
      read   : read
  };

};