// JavaScript Document

var isIE = (document.all) ? true: false;

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

/* 处理和jquery重复 */
var $_drag = function(id) {
    return "string" == typeof id ? document.getElementById(id) : id;
};

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

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

var Bind = function(object, fun) {
    return function() {
        return fun.apply(object, arguments);
    }
}

var BindAsEventListener = function(object, fun) {
    return function(event) {
        return fun.call(object, (event || window.event));
    }
}

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

function addEventHandler(oTarget, sEventType, fnHandler) {
    if (oTarget.addEventListener) {
        oTarget.addEventListener(sEventType, fnHandler, false);
    } else if (oTarget.attachEvent) {
        oTarget.attachEvent("on" + sEventType, fnHandler);
    } else {
        oTarget["on" + sEventType] = fnHandler;
    }
};

function removeEventHandler(oTarget, sEventType, fnHandler) {
    if (oTarget.removeEventListener) {
        oTarget.removeEventListener(sEventType, fnHandler, false);
    } else if (oTarget.detachEvent) {
        oTarget.detachEvent("on" + sEventType, fnHandler);
    } else {
        oTarget["on" + sEventType] = null;
    }
};

//拖放程序
var Drag = Class.create();
Drag.prototype = {
    //拖放对象
    initialize: function(drag, options) {
        //this.Drag = $(drag); //拖放对象
		this.Drag = $_drag(drag);
        this._x = this._y = 0; //记录鼠标相对拖放对象的位置
        this._marginLeft = this._marginTop = 0; //记录margin
        //事件对象(用于绑定移除事件)
        this._fM = BindAsEventListener(this, this.Move);
        this._fS = Bind(this, this.Stop);

        this.SetOptions(options);

        this.Limit = !!this.options.Limit;
        this.mxLeft = parseInt(this.options.mxLeft);
        this.mxRight = parseInt(this.options.mxRight);
        this.mxTop = parseInt(this.options.mxTop);
        this.mxBottom = parseInt(this.options.mxBottom);

        this.LockX = !!this.options.LockX;
        this.LockY = !!this.options.LockY;
        this.Lock = !!this.options.Lock;

        this.onStart = this.options.onStart;
        this.onMove = this.options.onMove;
        this.onStop = this.options.onStop;

//        this._Handle = $(this.options.Handle) || this.Drag;
//        this._mxContainer = $(this.options.mxContainer) || null;
        this._Handle = $_drag(this.options.Handle) || this.Drag;
        this._mxContainer = $_drag(this.options.mxContainer) || null;

        this.Drag.style.position = "absolute";
        //透明
        if (isIE && !!this.options.Transparent) {
            //填充拖放对象
            with(this._Handle.appendChild(document.createElement("div")).style) {
                width = height = "100%";
                backgroundColor = "#fff";
                filter = "alpha(opacity:0)";
                fontSize = 0;
            }
        }
        //修正范围
        this.Repair();
        addEventHandler(this._Handle, "mousedown", BindAsEventListener(this, this.Start));
    },
    //设置默认属性
    SetOptions: function(options) {
        this.options = { //默认值
            Handle: "",
            //设置触发对象（不设置则使用拖放对象）
            Limit: false,
            //是否设置范围限制(为true时下面参数有用,可以是负数)
            mxLeft: 0,
            //左边限制
            mxRight: 9999,
            //右边限制
            mxTop: 0,
            //上边限制
            mxBottom: 9999,
            //下边限制
            mxContainer: "",
            //指定限制在容器内
            LockX: false,
            //是否锁定水平方向拖放
            LockY: false,
            //是否锁定垂直方向拖放
            Lock: false,
            //是否锁定
            Transparent: false,
            //是否透明
            onStart: function() {},
            //开始移动时执行
            onMove: function() {},
            //移动时执行
            onStop: function() {} //结束移动时执行
        };
        Extend(this.options, options || {});
    },
    //准备拖动
    Start: function(oEvent) {
        if (this.Lock) {
            return;
        }
        this.Repair();
        //记录鼠标相对拖放对象的位置
        this._x = oEvent.clientX - this.Drag.offsetLeft;
        this._y = oEvent.clientY - this.Drag.offsetTop;
        //记录margin
        this._marginLeft = parseInt(CurrentStyle(this.Drag).marginLeft) || 0;
        this._marginTop = parseInt(CurrentStyle(this.Drag).marginTop) || 0;
        //mousemove时移动 mouseup时停止
        addEventHandler(document, "mousemove", this._fM);
        addEventHandler(document, "mouseup", this._fS);
        if (isIE) {
            //焦点丢失
            addEventHandler(this._Handle, "losecapture", this._fS);
            //设置鼠标捕获
            this._Handle.setCapture();
        } else {
            //焦点丢失
            addEventHandler(window, "blur", this._fS);
            //阻止默认动作
            oEvent.preventDefault();
        };
        //附加程序
        this.onStart();
    },
    //修正范围
    Repair: function() {
        if (this.Limit) {
            //修正错误范围参数
            this.mxRight = Math.max(this.mxRight, this.mxLeft + this.Drag.offsetWidth);
            this.mxBottom = Math.max(this.mxBottom, this.mxTop + this.Drag.offsetHeight);
            //如果有容器必须设置position为relative或absolute来相对或绝对定位，并在获取offset之前设置
            ! this._mxContainer || CurrentStyle(this._mxContainer).position == "relative" || CurrentStyle(this._mxContainer).position == "absolute" || (this._mxContainer.style.position = "relative");
        }
    },
    //拖动
    Move: function(oEvent) {
        //判断是否锁定
        if (this.Lock) {
            this.Stop();
            return;
        };
        //清除选择
        window.getSelection ? window.getSelection().removeAllRanges() : document.selection.empty();
        //设置移动参数
        var iLeft = oEvent.clientX - this._x,
        iTop = oEvent.clientY - this._y;
        //设置范围限制
        if (this.Limit) {
            //设置范围参数
            var mxLeft = this.mxLeft,
            mxRight = this.mxRight,
            mxTop = this.mxTop,
            mxBottom = this.mxBottom;
            //如果设置了容器，再修正范围参数
            if ( !! this._mxContainer) {
                mxLeft = Math.max(mxLeft, 0);
                mxTop = Math.max(mxTop, 0);
                mxRight = Math.min(mxRight, this._mxContainer.clientWidth);
                mxBottom = Math.min(mxBottom, this._mxContainer.clientHeight);
            };
            //修正移动参数
            iLeft = Math.max(Math.min(iLeft, mxRight - this.Drag.offsetWidth), mxLeft);
            iTop = Math.max(Math.min(iTop, mxBottom - this.Drag.offsetHeight), mxTop);
        }
        //设置位置，并修正margin
        if (!this.LockX) {
            this.Drag.style.left = iLeft - this._marginLeft + "px";
        }
        if (!this.LockY) {
            this.Drag.style.top = iTop - this._marginTop + "px";
        }
        //附加程序
        this.onMove();
    },
    //停止拖动
    Stop: function() {
        //移除事件
        removeEventHandler(document, "mousemove", this._fM);
        removeEventHandler(document, "mouseup", this._fS);
        if (isIE) {
            removeEventHandler(this._Handle, "losecapture", this._fS);
            this._Handle.releaseCapture();
        } else {
            removeEventHandler(window, "blur", this._fS);
        };
        //附加程序
        this.onStop();
    }
};