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

var Class = {
    create: function() {
        return function() {
            this.initialize.apply(this, arguments);
        }
    }
}

// 
Object.extend = function(destination, source) {
    for (var property in source) {
        destination[property] = source[property];
    }
    return destination;
}

var TransformView = Class.create();

// 
TransformView.prototype = {
    //容器对象,滑动对象,切换参数,切换数量
    initialize: function(container, slider, parameter, count, options) {
        if (parameter <= 0 || count <= 0) return;
        var oContainer = $(container),
        oSlider = $(slider),
        oThis = this;
        this.Index = 0; //当前索引

        this._timer = null; //定时器
        this._slider = oSlider; //滑动对象
        this._parameter = parameter; //切换参数
        this._count = count || 0; //切换数量
        this._target = 0; //目标参数

        this.SetOptions(options);

        this.Up = !!this.options.Up;
        this.Step = Math.abs(this.options.Step);
        this.Time = Math.abs(this.options.Time);
        this.Auto = !!this.options.Auto;
        this.Pause = Math.abs(this.options.Pause);
        this.onStart = this.options.onStart;
        this.onFinish = this.options.onFinish;

        oContainer.style.overflow = "hidden";
        oContainer.style.position = "relative";

        oSlider.style.position = "absolute";
        oSlider.style.top = oSlider.style.left = 0;
    },

    //设置默认属性
    SetOptions: function(options) {
        this.options = { //默认值
            Up: true,
            //是否向上(否则向左)
            Step: 5,
            //滑动变化率
            Time: 10,
            //滑动延时
            Auto: true,
            //是否自动转换
            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
        };
        Object.extend(this.options, options || {});
    },
    //开始切换设置
    Start: function() {
        if (this.Index < 0) {
            this.Index = this._count - 1;
        } else if (this.Index >= this._count) {
            this.Index = 0;
        }

        this._target = -1 * this._parameter * this.Index;
        this.onStart();
        this.Move();
    },
    //移动
    Move: function() {
        clearTimeout(this._timer);
        var oThis = this,
        style = this.Up ? "top": "left",
        iNow = parseInt(this._slider.style[style]) || 0,
        iStep = this.GetStep(this._target, iNow);

        if (iStep != 0) {
            this._slider.style[style] = (iNow + iStep) + "px";
            this._timer = setTimeout(function() {
                oThis.Move();
            },
            this.Time);
        } else {
            this._slider.style[style] = this._target + "px";
            this.onFinish();
            if (this.Auto) {
                this._timer = setTimeout(function() {
                    oThis.Index++;
                    oThis.Start();
                },
                this.Pause);
            }
        }
    },
    //获取步长
    GetStep: function(iTarget, iNow) {
        var iStep = (iTarget - iNow) / this.Step;
        if (iStep == 0) return 0;
        if (Math.abs(iStep) < 1) return (iStep > 0 ? 1 : -1);
        return iStep;
    },
    //停止
    Stop: function(iTarget, iNow) {
        clearTimeout(this._timer);
        this._slider.style[this.Up ? "top": "left"] = this._target + "px";
    }
};