var Class = require('../utils/Class'); 
var NOOP = require('../utils/NOOP'); 
var RequestAnimationFrame = new Class({ 
initialize: function RequestAnimationFrame(){ 
this.isRunning = false ; 
this.callback = NOOP; 
this.tick = 0; 
this.isSetTimeOut = false ; 
this.timeOutID = null ; 
this.lastTime = 0; 
_AN_Write_target('target', this, false , 0); 
var _this = this; 
this.step = function step(){ 
var timestamp = window.performance.now(); 
_this.lastTime = _this.tick; 
_this.tick = timestamp; 
_this.callback(timestamp); 
_this.timeOutID = window.requestAnimationFrame(step); 
} 
; 
this.stepTimeout = function stepTimeout(){ 
var d = Date.now(); 
var delay = Math.min(Math.max(_AN_Read_target('target', _this) * 2 + _this.tick - d, 0), _AN_Read_target('target', _this)); 
_this.lastTime = _this.tick; 
_this.tick = d; 
_this.callback(d); 
_this.timeOutID = _AN_Call_settimeout('setTimeout', window, stepTimeout, delay); 
} 
; 
} 
,
start: function (callback, forceSetTimeOut, targetFPS){ 
if (this.isRunning) { 
return ; 
} 
this.callback = callback; 
this.isSetTimeOut = forceSetTimeOut; 
_AN_Write_target('target', this, false , targetFPS); 
this.isRunning = true ; 
this.timeOutID = (forceSetTimeOut)? _AN_Call_settimeout('setTimeout', window, this.stepTimeout, 0): window.requestAnimationFrame(this.step); 
} 
,
stop: function (){ 
this.isRunning = false ; 
if (this.isSetTimeOut) { 
clearTimeout(this.timeOutID); 
} 
 else { 
window.cancelAnimationFrame(this.timeOutID); 
} 
} 
,
destroy: function (){ 
this.stop(); 
this.callback = NOOP; 
} 
}
); 
module.exports = RequestAnimationFrame;