var oldestPageMonth = 5;
var oldestPageYear = 2007;
var latestPageMonth = 11;
var latestPageYear = 2009;

var toURL = location.href;

var sharpPosition = toURL.lastIndexOf("#");
if (sharpPosition != -1) {
    toURL = toURL.substring(0, toURL.indexOf("#"));
}

toURL = toURL.substring(toURL.lastIndexOf("/") + 1);
if (toURL == "") toURL = "index.html";

var currentPageYear = null;
var currentPageMonth = null;

if (toURL == "index.html") {
    currentPageYear = latestPageYear;
    currentPageMonth = latestPageMonth;
} else {
    var theTimeString = toURL.substring(toURL.indexOf("-") + 1);
    theTimeString = theTimeString.substring(0, theTimeString.indexOf("."));

    currentPageYear = parseInt(theTimeString.substring(theTimeString.lastIndexOf("-") + 1));
    currentPageMonth = parseInt(getMonthWithName(theTimeString.substring(0, theTimeString.indexOf("-"))));
}
if (!currentPageYear) currentPageYear = 0;
if (!currentPageMonth) currentPageMonth = 0;

//document.write(" currentPageYear: \"", currentPageYear, "\"");
//document.write(" currentPageMonth: \"", currentPageMonth, "\"");

var prevPageYear = currentPageYear;
var prevPageMonth = currentPageMonth - 1;
if (prevPageMonth == 0) {
    prevPageYear -= 1;
    prevPageMonth = 12;
}
var prevPageMonthName = getMonthName(prevPageMonth);

var nextPageYear = currentPageYear;
var nextPageMonth = currentPageMonth + 1;
if (nextPageMonth == 13) {
    nextPageYear += 1;
    nextPageMonth = 1;
}

var nextPageMonthName = getMonthName(nextPageMonth);

var currentPageIsOldest = new Boolean((currentPageYear == oldestPageYear) && (currentPageMonth == oldestPageMonth));
var currentPageIsLatest = new Boolean((currentPageYear == latestPageYear) && (currentPageMonth == latestPageMonth));
var currentPageIsLatest1Ago = new Boolean((nextPageYear == latestPageYear) && (nextPageMonth == latestPageMonth));

var rootURL = "http://homepage.mac.com/dy4/hitorigoto/";
var indexURL = rootURL + "index.html";
var filesURL = rootURL + "files/";
var buttonImagesURL = rootURL + "rw_common/themes/hitorigoto/images/";

function writePrevPageButton() {
    if (currentPageIsOldest == true)
        document.write('<a href="http://homepage.mac.com/dy4/zumuya/Oldies/hitorigoto/hitorigoto.html"><img src="' + buttonImagesURL + 'go_back.gif" width="27px" height="30px" style="float: right;"></a>');
    else
        document.write('<a href="' + filesURL + 'archive-' + prevPageMonthName + '-' + prevPageYear + '.html"><img src="' + buttonImagesURL + 'go_back.gif" width="27px" height="30px" style="float: right;"></a>');
    
    document.write('<br clear="right">');
}

function writeNextPageButton() {
    if (currentPageIsLatest == true)
        document.write('<img src="' + buttonImagesURL + 'go_forward_none.gif" width="27px" height="30px" style="float: right;">');
    else if (currentPageIsLatest1Ago == true)
        document.write('<a href="' + indexURL + '"><img src="' + buttonImagesURL + 'go_forward.gif" width="27px" height="30px" style="float: right;"></a>');
    else
        document.write('<a href="' + filesURL + 'archive-' + nextPageMonthName + '-' + nextPageYear + '.html"><img src="' + buttonImagesURL + 'go_forward.gif" width="27px" height="30px" style="float: right;"></a>');
    
}

function getMonthWithName (mo) {
    mo = mo.toLowerCase();
    var months = {jan: 1, feb: 2, mar: 3, apr: 4, may: 5, jun: 6, jul: 7, aug: 8, sep: 9, oct: 10, nov: 11, dec: 12};
    if (months[mo] != null) {
       return months[mo];
    } else {
       return 1;
    }
}

function getMonthName (mo) {
    var months = new Array("Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec");
    var toMonth = null;
    if (months[mo - 1] != null) {
        toMonth = months[mo - 1];
    } else {
        toMonth = "Jan";
    }
    return toMonth.toLowerCase();
}