var toFn = function () {
    var lastTime = 0;
    var vendors = ['webkit', 'moz'];
    for (var x = 0; x < vendors.length && !window.requestAnimationFrame; ++x) {
        window.requestAnimationFrame = window[vendors[x] + 'RequestAnimationFrame'];
        window.cancelAnimationFrame =
            window[vendors[x] + 'CancelAnimationFrame'] || window[vendors[x] + 'CancelRequestAnimationFrame'];
    }

    if (!window.requestAnimationFrame)
        window.requestAnimationFrame = function (callback) {
            var currTime = new Date().getTime();
            var timeToCall = Math.max(0, 16 - (currTime - lastTime));
            var id = window.setTimeout(function () { callback(currTime + timeToCall); },
                timeToCall);
            lastTime = currTime + timeToCall;
            return id;
        };

    if (!window.cancelAnimationFrame)
        window.cancelAnimationFrame = function (id) {
            clearTimeout(id);
        };
};

var To=function (el, property, value, time, ease, onEnd,onChange ) {
    var current = el[property];
    var dv = value - current;
    var beginTime = new Date();
    var self = this;
    var currentEase=ease||function(a){return a };
    this.tickID=null;
    var toTick = function () {
        var dt = new Date() - beginTime;
        if (dt >= time) {
            el[property] = value;
            onChange && onChange(value);
            onEnd && onEnd(value);
            cancelAnimationFrame(self.tickID);
            self.toTick=null;
            return;
        }
        el[property] = dv * currentEase(dt / time) + current;
        self.tickID=requestAnimationFrame(toTick);
        //self.tickID = requestAnimationFrame(toTick);
        //cancelAnimationFrame必须在 tickID = requestAnimationFrame(toTick);的后面
        onChange && onChange(el[property]);
    };
    toTick();
    To.List.push(this);
};

To.List=[];

To.stopAll=function(){
    for(var i= 0,len=To.List.length;i<len;i++){
        cancelAnimationFrame(To.List[i].tickID);
    }
    To.List.length=0;
};

To.stop=function(to) {
    cancelAnimationFrame(to.tickID);
};

export {
	toFn,
	To
}