var NOOP = require('../utils/NOOP'); 
var RequestAnimationFrame = require('../dom/RequestAnimationFrame'); 
var Ticker = function (game, framerate){ 
this.game = game; 
this.raf = new RequestAnimationFrame(); 
this.started = false ; 
this.running = false ; 
this.lastUpdate = 0; 
this.gap = 1 / (framerate || 60); 
this.startTime = 0; 
this.elapsed = 0; 
this.time = 0; 
this.nextTime = 0; 
this.frame = 0; 
this.overlap = 0; 
this.fps = framerate; 
this.callback = NOOP; 
this.lagThreshold = 500; 
this.adjustedLag = 33; 
this.useRAF = true ; 
} 
; 
Ticker.prototype.constructor = Ticker; 
Ticker.prototype = { 
toString: function (){ 
return 'time: ' + this.time + ' elapsed: ' + this.elapsed + ' overlap: ' + this.overlap; 
} 
,
start: function (useRAF, callback){ 
if (this.started) { 
return this; 
} 
this.started = true ; 
this.running = true ; 
var now = window.performance.now(); 
this.startTime = now; 
this.lastUpdate = now; 
this.useRAF = useRAF; 
this.callback = callback; 
this.raf.start(this.step.bind(this), useRAF); 
} 
,
step: function (time, manual){ 
var elapsed = time - this.lastUpdate; 
if (elapsed > this.lagThreshold) { 
this.startTime += elapsed - this.adjustedLag; 
} 
this.lastUpdate += elapsed; 
var dt = (this.lastUpdate - this.startTime) / 1000; 
this.elapsed = elapsed; 
var overlap = dt - this.nextTime; 
this.overlap = overlap; 
this.time = dt; 
if (overlap > 0 || manual) { 
this.frame++ ; 
this.nextTime += overlap + ((overlap >= this.gap)? 0.004: this.gap - overlap); 
this.callback(elapsed); 
} 
} 
,
tick: function (){ 
this.step(true ); 
} 
,
lagSmoothing: function (threshold, adjustedLag){ 
this.lagThreshold = threshold || (1 / 1e-10); 
this.adjustedLag = Math.min(adjustedLag, this.lagThreshold, 0); 
} 
,
sleep: function (){ 
if (this.running) { 
this.raf.stop(); 
this.running = false ; 
} 
} 
,
wake: function (seamless){ 
if (this.running) { 
this.sleep(); 
} 
 else if (seamless) { 
this.startTime += - this.lastUpdate + (this.lastUpdate = Date.now()); 
} 
 else if (this.frame > 10) { 
this.lastUpdate = Date.now() - this.lagThreshold + 5; 
} 
this.raf.start(this.step.bind(this), this.useRAF); 
this.running = true ; 
this.step(true ); 
} 
,
setFps: function (value){ 
this.fps = value; 
this.gap = 1 / (value || 60); 
this.nextTime = this.time + this.gap; 
this.wake(); 
} 
,
getFps: function (){ 
return this.fps; 
} 
,
stop: function (){ 
this.running = false ; 
this.started = false ; 
this.raf.stop(); 
return this; 
} 
}
; 
module.exports = Ticker;