/**
 * created by zhousg on 2016/3/18.
 */
/**
 * @author zhousg
 * @date 2016-02-04
 * @method 滑动方法  针对一个大容器内部的容器做滑动封装
 * @param args args.swipedom 大容器对象  args.swipetype 滑动类型  args.swipedistance 缓冲距离
 * 注意：子容器的高宽度是取的内容的高宽 所以padding的大小有影响
 */
if(!window.itcast){
    window.itcast = {};
}
itcast.iscroll = function(args){
    /*调用的时候没有初始化的话就是初始化一次*/
    if(!(this instanceof arguments.callee)) return new arguments.callee(args);
    this.init(args);
};
itcast.iscroll.prototype = {
    constructor:itcast.iscroll,
    init:function(args){
        /*局部变量来接受当前的this*/
        var that  = this;
        /*如果传入的对象是一个dom对象就把他看作是我们的大容器盒子*/
        if(args.swipedom && typeof  args.swipedom == 'object'){
            that.parentdom = args.swipedom;
        }
        /*如果不存在父容器就停止初始化*/
        if(!that.parentdom) return false;
        /*找到子容器*/
        that.childdom = that.parentdom.children&&that.parentdom.children[0]?that.parentdom.children[0]:'';
        /*如果不存在子容器就停止初始化*/
        if(!that.childdom) return false;
        /*初始化传入的参数*/
        that.settings = {};
        /*默认类型  默认的y轴滑动 如果不是y的话就是以x轴开始滑动*/
        that.settings.swipetype = args.swipetype?args.swipetype:'y';
        /*默认的缓冲滑动距离*/
        that.settings.swipedistance = args.swipedistance>=0?args.swipedistance:150;
        /*初始化滑动*/
        that._scroll();
    },
    /*对外开放的设置定位的方法*/
    settranslate:function(translate){
        this.currpostion = translate;
        this._addtransition();
        this._changetranslate(this.currpostion);
    },
    _addtransition:function(){
        this.childdom.style.transition = "all .2s ease";
        this.childdom.style.webkittransition = "all .2s ease";/*兼容 老版本webkit内核浏览器*/
    },
    _removetransition:function(){
        this.childdom.style.transition = "none";
        this.childdom.style.webkittransition = "none";/*兼容 老版本webkit内核浏览器*/
    },
    _changetranslate:function(translate){
        if(this.settings.swipetype == 'y'){
            this.childdom.style.transform = "translatey("+translate+"px)";
            this.childdom.style.webkittransform = "translatey("+translate+"px)";
        }else{
            this.childdom.style.transform = "translatex("+translate+"px)";
            this.childdom.style.webkittransform = "translatex("+translate+"px)";
        }
    },
    _scroll:function(){
        /*局部变量来接受当前的this*/
        var that = this;
        /*滑动的类型*/
        var type = that.settings.swipetype == 'y'?true:false;
        /*父容器的高度或宽度*/
        var parentheight = type?that.parentdom.offsetheight:that.parentdom.offsetwidth;
        /*子容器的高度或宽度*/
        var childheight = type?that.childdom.offsetheight:that.childdom.offsetwidth;

        /*子容器没有父容器大的时候*/
        if(childheight < parentheight){
            if(type){
                that.childdom.style.height = parentheight + 'px';
                childheight = parentheight;
            }else{
                that.childdom.style.width = parentheight + 'px';
                childheight = parentheight;
            }
        }

        /*缓冲距离*/
        var distance = that.settings.swipedistance;
        /*区间*/
        /*左侧盒子定位的区间*/
        that.maxpostion = 0;
        that.minpostion = -(childheight-parentheight);
        /*设置滑动的当前位置*/
        that.currpostion = 0;
        that.startpostion = 0;
        that.endpostion = 0;
        that.movepostion = 0;
        /*1.滑动*/
        that.childdom.addeventlistener('touchstart',function(e){
            /*初始的y的坐标*/
            that.startpostion = type?e.touches[0].clienty: e.touches[0].clientx;
        },false);
        that.childdom.addeventlistener('touchmove',function(e){
            e.preventdefault();
            /*不停的做滑动的时候记录的endy的值*/
            that.endpostion = type?e.touches[0].clienty: e.touches[0].clientx;
            that.movepostion = that.startpostion - that.endpostion;/*计算了移动的距离*/

            /*2.滑动区间*/
            /*就是滑动区间*/
            if((that.currpostion-that.movepostion)<(that.maxpostion+distance)
                &&
                (that.currpostion-that.movepostion)>(that.minpostion -distance)){
                that._removetransition();
                that._changetranslate(that.currpostion-that.movepostion);
            }
        },false);
        window.addeventlistener('touchend',function(e){
            /*在限制滑动区间之后 重新计算当前定位*/
            /*判断是否在我们的合理定位区间内*/
            /*先向下滑动 */
            if((that.currpostion-that.movepostion) > that.maxpostion){
                that.currpostion = that.maxpostion;
                that._addtransition();
                that._changetranslate(that.currpostion);
            }
            /*想上滑动的时候*/
            else if((that.currpostion-that.movepostion) < that.minpostion){
                that.currpostion = that.minpostion;
                that._addtransition();
                that._changetranslate(that.currpostion);
            }
            /*正常的情况*/
            else{
                that.currpostion = that.currpostion-that.movepostion;
            }
            that._reset();
        },false);

    },
    _reset:function(){
        var that = this;
        that.startpostion = 0;
        that.endpostion = 0;
        that.movepostion = 0;
    }
};