var $ = function(id) {
    return "string" == typeof id ? document.getElementById(id) : id;
};

var Extend = function(destination, source) {
    for (var property in source) {
        destination[property] = source[property];
    }
    return destination;
}

var CurrentStyle = function(element) {
    return element.currentStyle || document.defaultView.getComputedStyle(element, null);
}

var Bind = function(object, fun) {
    var args = Array.prototype.slice.call(arguments).slice(2);
    return function() {
        return fun.apply(object, args.concat(Array.prototype.slice.call(arguments)));
    }
}

var Tween = {
    Quart: {
        easeOut: function(t, b, c, d) {
            return -c * ((t = t / d - 1) * t * t * t - 1) + b;
        }
    },
    Back: {
        easeOut: function(t, b, c, d, s) {
            if (s == undefined) s = 1.70158;
            return c * ((t = t / d - 1) * t * ((s + 1) * t + s) + 1) + b;
        }
    },
    Bounce: {
        easeOut: function(t, b, c, d) {
            if ((t /= d) < (1 / 2.75)) {
                return c * (7.5625 * t * t) + b;
            } else if (t < (2 / 2.75)) {
                return c * (7.5625 * (t -= (1.5 / 2.75)) * t + .75) + b;
            } else if (t < (2.5 / 2.75)) {
                return c * (7.5625 * (t -= (2.25 / 2.75)) * t + .9375) + b;
            } else {
                return c * (7.5625 * (t -= (2.625 / 2.75)) * t + .984375) + b;
            }
        }
    }
}


//容器对象,滑动对象,切换数量
var SlideTrans = function(container, slider, count, options) {
    this._slider = $(slider);
    this._container = $(container); //容器对象
    this._timer = null; //定时器
    this._count = Math.abs(count); //切换数量
    this._target = 0; //目标值
    this._t = this._b = this._c = 0; //tween参数

    this.Index = 0; //当前索引

    this.SetOptions(options);

    this.Auto = !!this.options.Auto;
    this.Duration = Math.abs(this.options.Duration);
    this.Time = Math.abs(this.options.Time);
    this.Pause = Math.abs(this.options.Pause);
    this.Tween = this.options.Tween;
    this.onStart = this.options.onStart;
    this.onFinish = this.options.onFinish;

    var bVertical = !!this.options.Vertical;
    this._css = bVertical ? "top" : "left"; //方向

    //样式设置
    var p = CurrentStyle(this._container).position;
    p == "relative" || p == "absolute" || (this._container.style.position = "relative");
    this._container.style.overflow = "hidden";
    this._slider.style.position = "absolute";

    this.Change = this.options.Change ? this.options.Change :
		this._slider[bVertical ? "offsetHeight" : "offsetWidth"] / this._count;
};
SlideTrans.prototype = {
    //设置默认属性
    SetOptions: function(options) {
        this.options = {//默认值
            Vertical: true, //是否垂直方向（方向不能改）
            Auto: true, //是否自动
            Change: 0, //改变量
            Duration: 50, //滑动持续时间
            Time: 10, //滑动延时
            Pause: 4000, //停顿时间(Auto为true时有效)
            onStart: function() { }, //开始转换时执行
            onFinish: function() { }, //完成转换时执行
            Tween: Tween.Quart.easeOut//tween算子
        };
        Extend(this.options, options || {});
    },
    //开始切换
    Run: function(index) {
        //修正index
        index == undefined && (index = this.Index);
        index < 0 && (index = this._count - 1) || index >= this._count && (index = 0);
        //设置参数
        this._target = -Math.abs(this.Change) * (this.Index = index);
        this._t = 0;
        this._b = parseInt(CurrentStyle(this._slider)[this.options.Vertical ? "top" : "left"]);
        this._c = this._target - this._b;

        this.onStart();
        this.Move();
    },
    //移动
    Move: function() {
        clearTimeout(this._timer);
        //未到达目标继续移动否则进行下一次滑动
        if (this._c && this._t < this.Duration) {
            this.MoveTo(Math.round(this.Tween(this._t++, this._b, this._c, this.Duration)));
            this._timer = setTimeout(Bind(this, this.Move), this.Time);
        } else {
            this.MoveTo(this._target);
            this.Auto && (this._timer = setTimeout(Bind(this, this.Next), this.Pause));
        }
    },
    //移动到
    MoveTo: function(i) {
        this._slider.style[this._css] = i + "px";
    },
    //下一个
    Next: function() {
        this.Run(++this.Index);
    },
    //上一个
    Previous: function() {
        this.Run(--this.Index);
    },
    //停止
    Stop: function() {
        clearTimeout(this._timer); this.MoveTo(this._target);
    }
};