var xmlhttp;
    var roll;
    var category;
    var timer;
        
    category = 0;
    roll = 0;

    function init(){
    
        category = 1;
        roll = 1;
    
        document.getElementById( 'article-focus-item-' + category).style.backgroundImage = 'url( ./images/bg_blue_medium_d.gif)';    
     
        beginRoll();
        
    }
    
    function beginRoll(){
        
        timer = setInterval( 'rollCategory()', 5000);         
        
    }
    
    function stopRoll(){
        
        clearInterval( timer);
        
    }
    
    function rollCategory(){
        
        roll ++;
        
        category = roll;

        getCategory( category);
        
        if( roll == 3) roll = 0;
        
    }
    
    function getCategory( si){

        var i;
        var url;
        
        category = si;
        
        roll = category;
        
        if( roll == 3) roll = 0;
        
        for( i = 1; i <= 3; i ++){
            
            if( i == si) document.getElementById( 'article-focus-item-' + i).style.backgroundImage = 'url( ./images/bg_blue_medium_d.gif)';
            
            else document.getElementById( 'article-focus-item-' + i).style.backgroundImage = 'url( ./images/bg_blue_medium_l.gif)';
            
        }

        url = './xml/xml_article_main_list.xml';

        if( window.XMLHttpRequest) xmlhttp = new XMLHttpRequest();
        else if( window.ActiveXObject) xmlhttp = new ActiveXObject('Microsoft.XMLHTTP');
        
        xmlhttp.open( 'GET', url, false);
              
        if( navigator.appName == 'Netscape'){

            xmlhttp.send( null);
            setCategory();
        
        }
        
        else{

            xmlhttp.onreadystatechange = setCategory;
            xmlhttp.send( null);
            
        } 
        
    }
    
    function setCategory(){
        
        var i;
        var xmlroot, xmlsingle;
        var serialno, subject, brief, thumb, url;

        if( xmlhttp.readyState == 4 && xmlhttp.status == 200){ 

            xmlroot = xmlhttp.responseXML.documentElement;

            xmlsingle = xmlroot.selectSingleNode('./result/item[@category=\'' + category + '\']');

            if( xmlsingle){
                
                serialno = xmlsingle.selectSingleNode('./serialno').firstChild.nodeValue;
                subject = xmlsingle.selectSingleNode('./subject').firstChild.nodeValue;
                brief = xmlsingle.selectSingleNode('./brief').firstChild.nodeValue;
                thumb = xmlsingle.selectSingleNode('./thumb').firstChild.nodeValue;
                
                url = 'article_view.aspx?sn=' + serialno;
                
                document.getElementById('article-focus-cover').innerHTML = '<a href="' + url + '"><img src="' + thumb + '" /></a>';
                document.getElementById('article-focus-text').innerHTML = '<h1><a href="' + url + '">' + subject + '</a></h1><span>' + brief + '</span>';
                document.getElementById('article-focus-read').innerHTML = '<a href="' + url + '"><span>閱讀全文</span></a><img src="./images/icon_blue_arrow.gif">';
                
            }

        }            
        
    }