// define global variables
var ajaxarea="";

function getDateContent(date,area)
{
    try 
    {
        xmlhttp = window.XMLHttpRequest?new XMLHttpRequest(): new ActiveXObject("Microsoft.XMLHTTP");
    }
    catch(e) 
    { 
        /* do nothing */
    }
 
    ajaxarea=area;

    xmlhttp.onreadystatechange = upDivCal; // when request finished, call the function to put result to destination DIVs
    rand=parseInt(Math.random()*99999999);  // create cache buster
    xmlhttp.open("GET", "infra/calander.php" + "?date=" + date + "&rand=" + rand); // use cache buster
    xmlhttp.send(null);
    return false;
}

function upDivCal() 
{
    document.getElementById(ajaxarea).innerHTML = xmlhttp.responseText;
}

function buildCalButtonLeft(m, y)
{
    day = "01";
    
    if(m < 10)
        var month = '0'+m;
    else
        var month = m;

    var button = '<a href="javascript:void(0);" onclick="changeCalander(\'down\',\''+day+month+y+'\');">';
    button += "<img src='img/arrow-left.jpg' class='leftbutton' alt='left'></a>";
    
    return button;
}

function buildCalButtonRight(m, y)
{
    day = "01";
    
    if(m < 10)
        var month = '0'+m;
    else
        var month = m;

    var button = '<a href="javascript:void(0);" onclick="changeCalander(\'up\',\''+day+month+y+'\');">';
    button += "<img src='img/arrow-right.jpg' class='rightbutton' alt='right'></a>";
    
    return button;
}

function getNewDate(m, y)
{
    day = "01";

    if(m < 10)
        var month = '0'+m;
    else
        var month = m;

    return day+month+y;
}

function changeCalander(direction,date)
{
    var curmonth = date.substr(2,2);
    var curyear  = date.substr(4,4);
    
    if(direction == "up")
    {
        mint = parseInt(curmonth, 10);
        yint = parseInt(curyear, 10);
        if(mint > 11)
        {
            mint = 1;
            yint = yint + 1;
        }
        else
        {
            mint = mint + 1;
        }
    }
    else if(direction == "down")
    {
        mint = parseInt(curmonth, 10);
        yint = parseInt(curyear, 10);
        if(mint == 1)
        {
            mint = 12;
            yint = yint - 1;
        }
        else
        {
            mint = mint - 1;
        }
    }
    
    newlb = buildCalButtonLeft(mint,yint);
    document.getElementById("calleft").innerHTML = newlb;
    
    newrb = buildCalButtonRight(mint,yint);
    document.getElementById("calright").innerHTML = newrb;
    
    newcal = buildCal(mint ,yint, "main", "month", "daysofweek", "days", 0);
    document.getElementById("cal").innerHTML = newcal;
    
    newdate = getNewDate(mint,yint);
    
    getDateContent(newdate,"biblereadingcontent");
}