/**
    * Lightbox
    *
    * This libary is used to create a lightbox in a web application.  This library
    * requires the Prototype 1.6 library and Script.aculo.us core, effects, and dragdrop
    * libraries.  To use, add a div containing the content to be displayed anywhere on
    * the page.  To create the lightbox, add the following code:
    *
    *	var test;
    *
    *	Event.observe(window, 'load', function () {
    *		test = new Lightbox('idOfMyDiv');
    *	});
    *
    *	Event.observe('lightboxLink', 'click', function () {
    *		test.open();
    *	});
    *
    *	Event.observe('closeLink', 'click', function () {
    *		test.close();
    *	});
    *
    */

    var Lightbox = Class.create({
        open : function () {
            this._centerWindow(this.container);
            this._fade('open', this.container);
        },

        close : function () {
            this._fade('close', this.container);
        },

        _fade : function fadeBg(userAction,whichDiv){
            if(userAction=='close'){
                new Effect.Opacity('bg_fade',
                           {duration:.5,
                            from:0.5,
                            to:0,
                            afterFinish:this._makeInvisible,
                            afterUpdate:this._hideLayer(whichDiv)});
            }else{
                new Effect.Opacity('bg_fade',
                           {duration:.5,
                            from:0,
                            to:0.5,
                            beforeUpdate:this._makeVisible,
                            afterFinish:this._showLayer(whichDiv)});
            }
        },

        _makeVisible : function makeVisible(){
            $("bg_fade").style.visibility="visible";
        },

        _makeInvisible : function makeInvisible(){
            $("bg_fade").style.visibility="hidden";
        },

        _showLayer : function showLayer(userAction){
            $(userAction).style.display="block";
        },

        _hideLayer : function hideLayer(userAction){
            $(userAction).style.display="none";
        },

        _centerWindow : function centerWindow(element) {
            var windowHeight = parseFloat($(element).getHeight())/2;
            var windowWidth = parseFloat($(element).getWidth())/2;

            if(typeof window.innerHeight != 'undefined') {
                $(element).style.top = Math.round(document.body.offsetTop + ((window.innerHeight - $(element).getHeight()))/2)+'px';
                $(element).style.left = Math.round(document.body.offsetLeft + ((window.innerWidth - $(element).getWidth()))/2)+'px';
            } else {
                $(element).style.top = Math.round(document.body.offsetTop + ((document.documentElement.offsetHeight - $(element).getHeight()))/2)+'px';
                $(element).style.left = Math.round(document.body.offsetLeft + ((document.documentElement.offsetWidth - $(element).getWidth()))/2)+'px';
            }
        },

        initialize : function(containerDiv) {
            this.container = containerDiv;
            if($('bg_fade') == null) {
                var screen = new Element('div', {'id': 'bg_fade'});
                document.body.appendChild(screen);
            }
            new Draggable(this.container);
            this._hideLayer(this.container);
        }
    });