var NOOP = require('../utils/NOOP'); 
var RequestAnimationFrame = require('../dom/RequestAnimationFrame'); 
var VariableTimeStep = function (game, framerate){ 
this.game = game; 
this.raf = new RequestAnimationFrame(); 
this.started = false ; 
this.running = false ; 
this.fps = framerate; 
this.callback = NOOP; 
this.useRAF = true ; 
this.time = 0; 
this.startTime = 0; 
this.lastTime = 0; 
this.delta = 0; 
this.deltaIndex = 0; 
this.deltaHistory = [] ; 
this.deltaSmoothingMax = 30; 
} 
; 
VariableTimeStep.prototype.constructor = VariableTimeStep; 
VariableTimeStep.prototype = { 
toString: function (){ 
return 'time: ' + this.time + ' delta: ' + this.delta; 
} 
,
start: function (useRAF, callback){ 
if (this.started) { 
return this; 
} 
this.started = true ; 
this.running = true ; 
this.time = Date.now(); 
this.startTime = Date.now(); 
this.lastTime = Date.now(); 
var history = [] ; 
for (var i = 0; 
i < this.deltaSmoothingMax; i++ ){ 
history[i] = 0; 
} 
this.delta = 0; 
this.deltaIndex = 0; 
this.deltaHistory = history; 
this.useRAF = useRAF; 
this.callback = callback; 
this.raf.start(this.step.bind(this), useRAF); 
} 
,
step: function (time){ 
var dt = (time - this.lastTime) / 1000; 
if (dt < 0 || dt > 1) { 
this.lastTime = time; 
return ; 
} 
dt = Math.max(Math.min(dt, 0.5), 0.0001); 
var idx = this.deltaIndex; 
var history = this.deltaHistory; 
var max = this.deltaSmoothingMax; 
history[idx] = dt; 
this.deltaIndex = (idx + 1) % max; 
var avg = 0; 
for (var i = 0; 
i < max; i++ ){ 
avg += history[i]; 
} 
avg /= max; 
this.delta = avg; 
this.time += avg; 
this.callback(this.time, avg * 1000); 
this.lastTime = time; 
} 
,
stop: function (){ 
this.running = false ; 
this.started = false ; 
this.raf.stop(); 
return this; 
} 
}
; 
module.exports = VariableTimeStep;