var Class = require('../utils/Class'); 
var GetValue = require('../utils/object/GetValue'); 
var NOOP = require('../utils/NOOP'); 
var RequestAnimationFrame = require('../dom/RequestAnimationFrame'); 
var TimeStep = new Class({ 
initialize: function TimeStep(game, config){ 
this.game = game; 
this.raf = new RequestAnimationFrame(); 
this.started = false ; 
this.running = false ; 
this.minFps = GetValue(config, 'min', 5); 
this.targetFps = GetValue(config, 'target', 60); 
this._min = 1000 / this.minFps; 
this._target = 1000 / this.targetFps; 
this.actualFps = this.targetFps; 
this.nextFpsUpdate = 0; 
this.framesThisSecond = 0; 
this.callback = NOOP; 
this.forceSetTimeOut = GetValue(config, 'forceSetTimeOut', false ); 
this.time = 0; 
this.startTime = 0; 
this.lastTime = 0; 
this.frame = 0; 
this.inFocus = true ; 
this._pauseTime = 0; 
this._coolDown = 0; 
this.delta = 0; 
this.deltaIndex = 0; 
this.deltaHistory = [] ; 
this.deltaSmoothingMax = GetValue(config, 'deltaHistory', 10); 
this.panicMax = GetValue(config, 'panicMax', 120); 
this.rawDelta = 0; 
this.now = 0; 
this.smoothStep = GetValue(config, 'smoothStep', true ); 
} 
,
blur: function (){ 
this.inFocus = false ; 
} 
,
focus: function (){ 
this.inFocus = true ; 
this.resetDelta(); 
} 
,
pause: function (){ 
this._pauseTime = window.performance.now(); 
} 
,
resume: function (){ 
this.resetDelta(); 
this.startTime += this.time - this._pauseTime; 
} 
,
resetDelta: function (){ 
var now = window.performance.now(); 
this.time = now; 
this.lastTime = now; 
this.nextFpsUpdate = now + 1000; 
this.framesThisSecond = 0; 
for (var i = 0; 
i < this.deltaSmoothingMax; i++ ){ 
this.deltaHistory[i] = Math.min(this._target, this.deltaHistory[i]); 
} 
this.delta = 0; 
this.deltaIndex = 0; 
this._coolDown = this.panicMax; 
} 
,
start: function (callback){ 
if (this.started) { 
return this; 
} 
this.started = true ; 
this.running = true ; 
for (var i = 0; 
i < this.deltaSmoothingMax; i++ ){ 
this.deltaHistory[i] = this._target; 
} 
this.resetDelta(); 
this.startTime = window.performance.now(); 
this.callback = callback; 
this.raf.start(this.step.bind(this), this.forceSetTimeOut, this._target); 
} 
,
step: function (){ 
var time = window.performance.now(); 
this.now = time; 
var before = time - this.lastTime; 
if (before < 0) { 
before = 0; 
} 
this.rawDelta = before; 
var idx = this.deltaIndex; 
var history = this.deltaHistory; 
var max = this.deltaSmoothingMax; 
var dt = before; 
var avg = before; 
if (this.smoothStep) { 
if (this._coolDown > 0 || !this.inFocus) { 
this._coolDown-- ; 
dt = Math.min(dt, this._target); 
} 
if (dt > this._min) { 
dt = history[idx]; 
dt = Math.min(dt, this._min); 
} 
history[idx] = dt; 
this.deltaIndex++ ; 
if (this.deltaIndex > max) { 
this.deltaIndex = 0; 
} 
avg = 0; 
for (var i = 0; 
i < max; i++ ){ 
avg += history[i]; 
} 
avg /= max; 
} 
this.delta = avg; 
this.time += this.rawDelta; 
if (time > this.nextFpsUpdate) { 
this.actualFps = 0.25 * this.framesThisSecond + 0.75 * this.actualFps; 
this.nextFpsUpdate = time + 1000; 
this.framesThisSecond = 0; 
} 
this.framesThisSecond++ ; 
var interpolation = avg / this._target; 
this.callback(time, avg, interpolation); 
this.lastTime = time; 
this.frame++ ; 
} 
,
tick: function (){ 
this.step(); 
} 
,
sleep: function (){ 
if (this.running) { 
this.raf.stop(); 
this.running = false ; 
} 
} 
,
wake: function (seamless){ 
if (this.running) { 
return ; 
} 
 else if (seamless) { 
this.startTime += - this.lastTime + (this.lastTime + window.performance.now()); 
} 
this.raf.start(this.step.bind(this), this.useRAF); 
this.running = true ; 
this.step(); 
} 
,
getDuration: function (){ 
return Math.round(this.lastTime - this.startTime) / 1000; 
} 
,
getDurationMS: function (){ 
return Math.round(this.lastTime - this.startTime); 
} 
,
stop: function (){ 
this.running = false ; 
this.started = false ; 
this.raf.stop(); 
return this; 
} 
,
destroy: function (){ 
this.stop(); 
this.callback = NOOP; 
this.raf = null ; 
this.game = null ; 
} 
}
); 
module.exports = TimeStep;