/**
 * Created by yj on 16/5/1.
 */
class Animator{
    constructor(duration,progress,easing){
        this.duration = duration
        this.progress = progress
        this.easing = easing || function(p) { return p}
    }
    start(finished){
        var startTime = Date.now()
        var duration = this.duration,
            self = this;
        requestAnimationFrame(function step(){
            var p = (Date.now() - startTime) / duration;
            var next = true;

            if(p < 1.0){
                self.progress(self.easing(p),p);
            }else{
                if(typeof finished === 'function'){
                    next = finished() === false;
                }else{
                    next = finished === false;
                }
                if(!next){
                    self.progress(self.easing(1.0),1.0)
                }else{
                    startTime += duration;
                    self.progress(self.easing(p),p)
                }
            }
            if(next){
                requestAnimationFrame(step);
            }
        })
    }
}
class AnimationQueue{
    constructor(animators){
        this.animators = animators || []
    }
    append(...args){
        this.animators.push.apply(this.animators,args)
    }
    flush(){
        if(this.animators.length){
            var self = this
            function play(){
                var animator = self.animators.shift()
                if(animator instanceof  Animator) {
                    animator.start(function () {
                        if (self.animators.length) {
                            play();
                        }
                    })
                }else{
                    animator.apply(self)
                    if(self.animators.length){
                        play()
                    }
                }
            }
            play()
        }
    }
}