var $ = require('jquery');

var _count = 0;
var _isIE6 = !('minWidth' in $('html')[0].style);
var _isFixed = !_isIE6;


function Popup() {

    this.destroyed = false;


    this.__popup = $('<div />')
        /*使用 <dialog /> 元素可能导致 z-index 永远置顶的问题(chrome)*/
        .css({
            display: 'none',
            position: 'absolute',
            /*
            left: 0,
            top: 0,
            bottom: 'auto',
            right: 'auto',
            margin: 0,
            padding: 0,
            border: '0 none',
            background: 'transparent'
            */
            outline: 0
        })
        .attr('tabindex', '-1')
        .html(this.innerHTML)
        .appendTo('body');


    this.__backdrop = this.__mask = $('<div />')
        .css({
            opacity: .7,
            background: '#000'
        });


    // 使用 HTMLElement 作为外部接口使用，而不是 jquery 对象
    // 统一的接口利于未来 Popup 移植到其他 DOM 库中
    this.node = this.__popup[0];
    this.backdrop = this.__backdrop[0];

    _count++;
}


$.extend(Popup.prototype, {

    /**
     * 初始化完毕事件，在 show()、showModal() 执行
     * @name Popup.prototype.onshow
     * @event
     */

    /**
     * 关闭事件，在 close() 执行
     * @name Popup.prototype.onclose
     * @event
     */

    /**
     * 销毁前事件，在 remove() 前执行
     * @name Popup.prototype.onbeforeremove
     * @event
     */

    /**
     * 销毁事件，在 remove() 执行
     * @name Popup.prototype.onremove
     * @event
     */

    /**
     * 重置事件，在 reset() 执行
     * @name Popup.prototype.onreset
     * @event
     */

    /**
     * 焦点事件，在 foucs() 执行
     * @name Popup.prototype.onfocus
     * @event
     */

    /**
     * 失焦事件，在 blur() 执行
     * @name Popup.prototype.onblur
     * @event
     */

    /** 浮层 DOM 素节点[*] */
    node: null,

    /** 遮罩 DOM 节点[*] */
    backdrop: null,

    /** 是否开启固定定位[*] */
    fixed: false,

    /** 判断对话框是否删除[*] */
    destroyed: true,

    /** 判断对话框是否显示 */
    open: false,

    /** close 返回值 */
    returnValue: '',

    /** 是否自动聚焦 */
    autofocus: true,

    /** 对齐方式[*] */
    align: 'bottom left',

    /** 内部的 HTML 字符串 */
    innerHTML: '',

    /** CSS 类名 */
    className: 'ui-popup',

    /**
     * 显示浮层
     * @param   {HTMLElement, Event}  指定位置（可选）
     */
    show: function(anchor) {

        if (this.destroyed) {
            return this;
        }

        var that = this;
        var popup = this.__popup;
        var backdrop = this.__backdrop;

        this.__activeElement = this.__getActive();

        this.open = true;
        this.follow = anchor || this.follow;


        // 初始化 show 方法
        if (!this.__ready) {

            popup
                .addClass(this.className)
                .attr('role', this.modal ? 'alertdialog' : 'dialog')
                .css('position', this.fixed ? 'fixed' : 'absolute');

            if (!_isIE6) {
                $(window).on('resize', $.proxy(this.reset, this));
            }

            // 模态浮层的遮罩
            if (this.modal) {
                var backdropCss = {
                    position: 'fixed',
                    left: 0,
                    top: 0,
                    width: '100%',
                    height: '100%',
                    overflow: 'hidden',
                    userSelect: 'none',
                    zIndex: this.zIndex || Popup.zIndex
                };


                popup.addClass(this.className + '-modal');


                if (!_isFixed) {
                    $.extend(backdropCss, {
                        position: 'absolute',
                        width: $(window).width() + 'px',
                        height: $(document).height() + 'px'
                    });
                }


                backdrop
                    .css(backdropCss)
                    .attr({ tabindex: '0' })
                    .on('focus', $.proxy(this.focus, this));

                // 锁定 tab 的焦点操作
                this.__mask = backdrop
                    .clone(true)
                    .attr('style', '')
                    .insertAfter(popup);

                backdrop
                    .addClass(this.className + '-backdrop')
                    .insertBefore(popup);

                this.__ready = true;
            }


            if (!popup.html()) {
                popup.html(this.innerHTML);
            }
        }


        popup
            .addClass(this.className + '-show')
            .show();

        backdrop.show();


        this.reset().focus();
        this.__dispatchEvent('show');

        return this;
    },


    /** 显示模态浮层。参数参见 show() */
    showModal: function() {
        this.modal = true;
        return this.show.apply(this, arguments);
    },


    /** 关闭浮层 */
    close: function(result) {

        if (!this.destroyed && this.open) {

            if (result !== undefined) {
                this.returnValue = result;
            }

            this.__popup.hide().removeClass(this.className + '-show');
            this.__backdrop.hide();
            this.open = false;
            this.blur(); // 恢复焦点，照顾键盘操作的用户
            this.__dispatchEvent('close');
        }

        return this;
    },


    /** 销毁浮层 */
    remove: function() {

        if (this.destroyed) {
            return this;
        }

        this.__dispatchEvent('beforeremove');

        if (Popup.current === this) {
            Popup.current = null;
        }


        // 从 DOM 中移除节点
        this.__popup.remove();
        this.__backdrop.remove();
        this.__mask.remove();


        if (!_isIE6) {
            $(window).off('resize', this.reset);
        }


        this.__dispatchEvent('remove');

        for (var i in this) {
            delete this[i];
        }

        return this;
    },


    /** 重置位置 */
    reset: function() {

        var elem = this.follow;

        if (elem) {
            this.__follow(elem);
        } else {
            this.__center();
        }

        this.__dispatchEvent('reset');

        return this;
    },


    /** 让浮层获取焦点 */
    focus: function() {

        var node = this.node;
        var popup = this.__popup;
        var current = Popup.current;
        var index = this.zIndex = Popup.zIndex++;

        if (current && current !== this) {
            current.blur(false);
        }

        // 检查焦点是否在浮层里面
        if (!$.contains(node, this.__getActive())) {
            var autofocus = popup.find('[autofocus]')[0];

            if (!this._autofocus && autofocus) {
                this._autofocus = true;
            } else {
                autofocus = node;
            }

            this.__focus(autofocus);
        }

        // 设置叠加高度
        popup.css('zIndex', index);
        //this.__backdrop.css('zIndex', index);

        Popup.current = this;
        popup.addClass(this.className + '-focus');

        this.__dispatchEvent('focus');

        return this;
    },


    /** 让浮层失去焦点。将焦点退还给之前的元素，照顾视力障碍用户 */
    blur: function() {

        var activeElement = this.__activeElement;
        var isBlur = arguments[0];


        if (isBlur !== false) {
            this.__focus(activeElement);
        }

        this._autofocus = false;
        this.__popup.removeClass(this.className + '-focus');
        this.__dispatchEvent('blur');

        return this;
    },


    /**
     * 添加事件
     * @param   {String}    事件类型
     * @param   {Function}  监听函数
     */
    addEventListener: function(type, callback) {
        this.__getEventListener(type).push(callback);
        return this;
    },


    /**
     * 删除事件
     * @param   {String}    事件类型
     * @param   {Function}  监听函数
     */
    removeEventListener: function(type, callback) {
        var listeners = this.__getEventListener(type);
        for (var i = 0; i < listeners.length; i++) {
            if (callback === listeners[i]) {
                listeners.splice(i--, 1);
            }
        }
        return this;
    },


    // 获取事件缓存
    __getEventListener: function(type) {
        var listener = this.__listener;
        if (!listener) {
            listener = this.__listener = {};
        }
        if (!listener[type]) {
            listener[type] = [];
        }
        return listener[type];
    },


    // 派发事件
    __dispatchEvent: function(type) {
        var listeners = this.__getEventListener(type);

        if (this['on' + type]) {
            this['on' + type]();
        }

        for (var i = 0; i < listeners.length; i++) {
            listeners[i].call(this);
        }
    },


    // 对元素安全聚焦
    __focus: function(elem) {
        // 防止 iframe 跨域无权限报错
        // 防止 IE 不可见元素报错
        try {
            // ie11 bug: iframe 页面点击会跳到顶部
            if (this.autofocus && !/^iframe$/i.test(elem.nodeName)) {
                elem.focus();
            }
        } catch (e) {}
    },


    // 获取当前焦点的元素
    __getActive: function() {
        try { // try: ie8~9, iframe #26
            var activeElement = document.activeElement;
            var contentDocument = activeElement.contentDocument;
            var elem = contentDocument && contentDocument.activeElement || activeElement;
            return elem;
        } catch (e) {}
    },


    // 居中浮层
    __center: function() {

        var popup = this.__popup;
        var $window = $(window);
        var $document = $(document);
        var fixed = this.fixed;
        var dl = fixed ? 0 : $document.scrollLeft();
        var dt = fixed ? 0 : $document.scrollTop();
        var ww = $window.width();
        var wh = $window.height();
        var ow = popup.width();
        var oh = popup.height();
        var left = (ww - ow) / 2 + dl;
        var top = (wh - oh) * 382 / 1000 + dt; // 黄金比例
        var style = popup[0].style;


        style.left = Math.max(parseInt(left), dl) + 'px';
        style.top = Math.max(parseInt(top), dt) + 'px';
    },


    // 指定位置 @param    {HTMLElement, Event}  anchor
    __follow: function(anchor) {

        var $elem = anchor.parentNode && $(anchor);
        var popup = this.__popup;


        if (this.__followSkin) {
            popup.removeClass(this.__followSkin);
        }


        // 隐藏元素不可用
        if ($elem) {
            var o = $elem.offset();
            if (o.left * o.top < 0) {
                return this.__center();
            }
        }

        var that = this;
        var fixed = this.fixed;

        var $window = $(window);
        var $document = $(document);
        var winWidth = $window.width();
        var winHeight = $window.height();
        var docLeft = $document.scrollLeft();
        var docTop = $document.scrollTop();


        var popupWidth = popup.width();
        var popupHeight = popup.height();
        var width = $elem ? $elem.outerWidth() : 0;
        var height = $elem ? $elem.outerHeight() : 0;
        var offset = this.__offset(anchor);
        var x = offset.left;
        var y = offset.top;
        var left = fixed ? x - docLeft : x;
        var top = fixed ? y - docTop : y;


        var minLeft = fixed ? 0 : docLeft;
        var minTop = fixed ? 0 : docTop;
        var maxLeft = minLeft + winWidth - popupWidth;
        var maxTop = minTop + winHeight - popupHeight;


        var css = {};
        var align = this.align.split(' ');
        var className = this.className + '-';
        var reverse = { top: 'bottom', bottom: 'top', left: 'right', right: 'left' };
        var name = { top: 'top', bottom: 'top', left: 'left', right: 'left' };


        var temp = [{
            top: top - popupHeight,
            bottom: top + height,
            left: left - popupWidth,
            right: left + width
        }, {
            top: top,
            bottom: top - popupHeight + height,
            left: left,
            right: left - popupWidth + width
        }];


        var center = {
            left: left + width / 2 - popupWidth / 2,
            top: top + height / 2 - popupHeight / 2
        };


        var range = {
            left: [minLeft, maxLeft],
            top: [minTop, maxTop]
        };


        // 超出可视区域重新适应位置
        $.each(align, function(i, val) {

            // 超出右或下边界：使用左或者上边对齐
            if (temp[i][val] > range[name[val]][1]) {
                val = align[i] = reverse[val];
            }

            // 超出左或右边界：使用右或者下边对齐
            if (temp[i][val] < range[name[val]][0]) {
                align[i] = reverse[val];
            }

        });


        // 一个参数的情况
        if (!align[1]) {
            name[align[1]] = name[align[0]] === 'left' ? 'top' : 'left';
            temp[1][align[1]] = center[name[align[1]]];
        }


        //添加follow的css, 为了给css使用
        className += align.join('-') + ' ' + this.className + '-follow';

        that.__followSkin = className;


        if ($elem) {
            popup.addClass(className);
        }


        css[name[align[0]]] = parseInt(temp[0][align[0]]);
        css[name[align[1]]] = parseInt(temp[1][align[1]]);
        popup.css(css);

    },


    // 获取元素相对于页面的位置（包括iframe内的元素）
    // 暂时不支持两层以上的 iframe 套嵌
    __offset: function(anchor) {

        var isNode = anchor.parentNode;
        var offset = isNode ? $(anchor).offset() : {
            left: anchor.pageX,
            top: anchor.pageY
        };


        anchor = isNode ? anchor : anchor.target;
        var ownerDocument = anchor.ownerDocument;
        var defaultView = ownerDocument.defaultView || ownerDocument.parentWindow;

        if (defaultView == window) { // IE <= 8 只能使用两个等于号
            return offset;
        }

        // {Element: Ifarme}
        var frameElement = defaultView.frameElement;
        var $ownerDocument = $(ownerDocument);
        var docLeft = $ownerDocument.scrollLeft();
        var docTop = $ownerDocument.scrollTop();
        var frameOffset = $(frameElement).offset();
        var frameLeft = frameOffset.left;
        var frameTop = frameOffset.top;

        return {
            left: offset.left + frameLeft - docLeft,
            top: offset.top + frameTop - docTop
        };
    }

});


/** 当前叠加高度 */
Popup.zIndex = 1024;


/** 顶层浮层的实例 */
Popup.current = null;


module.exports = Popup;