var isDOM = (document.getElementById ? true : false);

var isIE4 = ((document.all && !isDOM) ? true : false);

var isNS4 = (document.layers ? true : false);

function getRef(id)
{
    if (isDOM)
        return document.getElementById(id);

    if (isIE4)
        return document.all[id];

    if (isNS4)
        return document.layers[id];
}

function getSty(id)
{
    return (isNS4 ? getRef(id) : getRef(id).style);
}

// Hide timeout.

var popTimer = 0;

// Array showing highlighted menu items.

var litNow = new Array();

function popOver(menuNum, itemNum)
{
    clearTimeout(popTimer);

    hideAllBut(menuNum);

    litNow = getTree(menuNum, itemNum);

    changeCol(litNow, true);

    targetNum = menu[menuNum][itemNum].target;

    if (targetNum > 0)
    {
        thisX = parseInt(menu[menuNum][0].ref.left) +
            parseInt(menu[menuNum][itemNum].ref.left);

        thisY = parseInt(menu[menuNum][0].ref.top) +
            parseInt(menu[menuNum][itemNum].ref.top);

        with (menu[targetNum][0].ref)
        {
            left = parseInt(thisX + menu[targetNum][0].x);

            top = parseInt(thisY + menu[targetNum][0].y);

            visibility = 'visible';
          }
       }
}

function popOut(menuNum, itemNum)
{
    if ((menuNum == 0) && !menu[menuNum][itemNum].target)
        hideAllBut(0);
    else
        popTimer = setTimeout('hideAllBut(0)', 500);
}

function getTree(menuNum, itemNum)
{
    // Array index is the menu number. The contents are null (if that menu is not a parent)
    // or the item number in that menu that is an ancestor (to light it up).

    itemArray = new Array(menu.length);

    while(1)
    {
        itemArray[menuNum] = itemNum;

        // If we've reached the top of the hierarchy, return.

        if (menuNum == 0)
            return itemArray;

        itemNum = menu[menuNum][0].parentItem;

        menuNum = menu[menuNum][0].parentMenu;
   }
}

// Pass an array and a boolean to specify colour change, true = over colour.

function changeCol(changeArray, isOver)
{
    for (menuCount = 0; menuCount < changeArray.length; menuCount++)
    {
        if (changeArray[menuCount])
        {
            newCol = (isOver ? menu[menuCount][0].overCol :
                menu[menuCount][0].backCol);

            // Change the colours of the div/layer background.

            with (menu[menuCount][changeArray[menuCount]].ref)
            {
                if (isNS4)
                    bgColor = newCol;
                else
                    backgroundColor = newCol;
            }
       }
    }
}

function hideAllBut(menuNum)
{
    var keepMenus = getTree(menuNum, 1);

    for (count = 0; count < menu.length; count++)
        if (!keepMenus[count])
            menu[count][0].ref.visibility = 'hidden';

    changeCol(litNow, false);
}

// *** MENU CONSTRUCTION FUNCTIONS ***

function Menu(isVert,
              popInd,
              x,
              y,
              width,
              overCol,
              backCol,
              borderClass,
              textClass)
{
    // True or false - a vertical menu?

    this.isVert = isVert;

    // The popout indicator used (if any) for this menu.

    this.popInd = popInd

    // Position and size settings.

    this.x = x;
    this.y = y;
    this.width = width;

    // Colours of menu and items.

    this.overCol = overCol;
    this.backCol = backCol;

    // The stylesheet class used for item borders and the text within items.

    this.borderClass = borderClass;
    this.textClass = textClass;

    // Parent menu and item numbers, indexed later.

    this.parentMenu = null;
    this.parentItem = null;

    // Reference to the object's style properties (set later).

    this.ref = null;
}

function Item(text, href, frame, length, spacing, target)
{
    this.text = text;

    this.href = href;

    this.frame = frame;

    this.length = length;

    this.spacing = spacing;

    this.target = target;

    // Reference to the object's style properties (set later).

    this.ref = null;
}

function writeMenus()
{
    if (!isDOM && !isIE4 && !isNS4)
        return;

    for (currMenu = 0; currMenu < menu.length; currMenu++)
    {
        with (menu[currMenu][0])
        {

            // Variable for holding HTML for items and positions of next item.

            var str = '', itemX = 0, itemY = 0;

            // Remember, items start from 1 in the array (0 is menu object
            // itself, above).  Also use properties of each item nested in
            // the other with() for construction.

            for (currItem = 1; currItem < menu[currMenu].length; currItem++)
            {
                with (menu[currMenu][currItem]) {

                    var itemID = 'menu' + currMenu + 'item' + currItem;

                    // The width and height of the menu item - dependent on
                    // orientation!

                    var w = (isVert ? width : length);

                    var h = (isVert ? length : width);

                    // Create a div or layer text string with appropriate
                    // styles/properties.  Thanks to Paul Maden
                    // (www.paulmaden.com) for helping debug this in IE4,
                    // apparently the width must be a miniumum of 3 for it
                    // to work in that browser.

                    if (isDOM || isIE4)
                    {
                        str += '<div align="center" id="' + itemID +
                            '" style="position: absolute; left: ' + itemX +
                            '; top: ' + itemY + '; width: ' + w +
                            '; height: ' + h + '; visibility: inherit; ' +
                            'font-family: arial; ';

                        if (backCol)
                            str += 'background: ' + backCol + '; ';

                        str += '" ';
                    }

                    if (isNS4)
                    {
                        str += '<layer id="' + itemID + '" left="' + itemX +
                            '" top="' + itemY + '" width="' +  w +
                            '" height="' + h + '" visibility="inherit" ';

                        if (backCol)
                            str += 'bgcolor="' + backCol + '" ';
                    }

                    if (borderClass)
                        str += 'class="' + borderClass + '" ';

                    // Add mouseover handlers and finish div/layer.

                    str += 'onMouseOver="popOver(' + currMenu + ',' +
                        currItem + ')" onMouseOut="popOut(' + currMenu +
                        ',' + currItem + ')">';

                    // Add contents of item (default: table with link inside).
                    // In IE/NS6+, add padding if there's a border to emulate
                    // NS4's layer padding.  If a target frame is specified,
                    // also add that to the <a> tag.

                    str += '<table width="' + (w - 8) +
                        '" border="0" cellspacing="0" cellpadding="' +
                        (!isNS4 && borderClass ? 3 : 0) +
                        '"><tr><td align="center" height="' + (h - 7) +
                        '">' + '<a class="' + textClass + '" href="' + href +
                        '"' + (frame ? ' target="' + frame + '">' : '>') +
                        text + '</a></td>';

                    if (target > 0)
                    {
                        // Set target's parents to this menu item.
                        menu[target][0].parentMenu = currMenu;
                        menu[target][0].parentItem = currItem;

                        // Add a popout indicator.
                        if (popInd)
                            str += '<td class="' + textClass +
                            '" align="right">' + popInd + '</td>';
                    }

                    str += '</tr></table>' + (isNS4 ? '</layer>' : '</div>');

                    if (isVert)
                        itemY += length + spacing;
                    else
                        itemX += length + spacing;
                }
            }

            if (isDOM)
            {
                var newDiv = document.createElement('div');

                document.getElementsByTagName('body').item(0).
                    appendChild(newDiv);

                newDiv.innerHTML = str;

                ref = newDiv.style;

                ref.position = 'absolute';

                ref.visibility = 'hidden';
            }

            // Insert a div tag to the end of the BODY with menu HTML in place
            // for IE4.

            if (isIE4)
            {
                document.body.insertAdjacentHTML('beforeEnd',
                                                '<div id="menu' + currMenu +
                                                    'div" ' +
                                                    'style="position: absolute; visibility: hidden">' + str + '</div>');

                ref = getSty('menu' + currMenu + 'div');
            }

            // In NS4, create a reference to a new layer and write the items
            // to it.

            if (isNS4)
            {
                ref = new Layer(0);

                ref.document.write(str);

                ref.document.close();
            }

            for (currItem = 1; currItem < menu[currMenu].length; currItem++)
            {
                itemName = 'menu' + currMenu + 'item' + currItem;

                if (isDOM || isIE4)
                    menu[currMenu][currItem].ref = getSty(itemName);

                if (isNS4)
                    menu[currMenu][currItem].ref = ref.document[itemName];
            }
        }
    }

    with(menu[0][0])
    {
        ref.left = x;

        ref.top = y;

        ref.visibility = 'visible';
    }
}

// Syntaxes: *** START EDITING HERE, READ THIS SECTION CAREFULLY! ***
//
// menu[menuNumber][0] = new Menu(Vertical menu? (true/false), 'popout indicator', left, top,
// width, 'mouseover colour', 'background colour', 'border stylesheet', 'text stylesheet');
//
// Left and Top are measured on-the-fly relative to the top-left corner of its trigger, or
// for the root menu, the top-left corner of the page.
//
// menu[menuNumber][itemNumber] = new Item('Text', 'URL', 'target frame', length of menu item,
//  additional spacing to next menu item, number of target menu to popout);
//
// If no target menu (popout) is desired, set it to 0. Likewise, if your site does not use
// frames, pass an empty string as a frame target.
//
// Something that needs explaining - the Vertical Menu setup. You can see most menus below
// are 'true', that is they are vertical, except for the first root menu. The 'length' and
// 'width' of an item depends on its orientation -- length is how long the item runs for in
// the direction of the menu, and width is the lateral dimension of the menu. Just look at
// the examples and tweak the numbers, they'll make sense eventually :').

    var menu = new Array();

    // Default colours passed to most menu constructors (just passed to functions, not
    // a global variable - makes things easier to change later in bulk).

    var defOver = '#006400', defBack = '#003366';

    // Default 'length' of menu items - item height if menu is vertical, width if horizontal.

    var defLength = 22;

    var vertSpacing = 2;

    var menu0Length = 20;

    // Menu 0 is the special, 'root' menu from which everything else arises.

    menu[0] = new Array();

    // A non-vertical menu with a few different colours and no popout indicator, as an example.
    // *** MOVE ROOT MENU AROUND HERE ***  it's positioned at (5, 0) and is 17px high now.

    menu[0][0] = new Menu(true,
                          '',
                          80,
                          225,
                          55,
                          '#006400',
                          '#006666',
                          '',
                          'itemText');

    var today = new Date();

    // MS IE returns 4-digit year for getYear(), even though it's supposed to
    // return the number of years since 1900.  'getFullYear()' gives the desired
    // value (4-digit year) in all cases, but it wasn't implemented in earlier
    // versions (hence the conditional statement).

    var currYear = (today.getFullYear ? today.getFullYear() : today.getYear());

    if (currYear < 1900)
        currYear += 1900;

    var currDecade = Math.floor(currYear / 10) * 10;

    // getMonth() returns 0 - 11 for January - December.

    var currMonth = today.getMonth();

    var decadeIndex = 1;

    for (decade = 1950; decade <= currDecade; decade += 10, decadeIndex++)
    {
        menu[0][decadeIndex] = new Item(decade + "s",
                                        '#',
                                        '',
                                        menu0Length,
                                        vertSpacing,
                                        decadeIndex);

        menu[decadeIndex] = new Array();

        menu[decadeIndex][0] = new Menu(true,
                                        '',
                                        60,
                                        0,
                                        55,
                                        defOver,
                                        defBack,
                                        'itemBorder',
                                        'itemText');

        for (yearIndex = 0; yearIndex < 10; yearIndex++)
        {
            var url = "cgi/wrhs.cgi?year=" + (decade + yearIndex);

            var yearText = decade + yearIndex;

            if ((decade == 1950) && (yearIndex < 5))
            {
                url = "";

                yearText = "-";
            }
            else if ((yearText > currYear) ||
                ((yearText == currYear) && (currMonth < 5)))
                break;

            menu[decadeIndex][yearIndex + 1] = new Item(yearText,
                                                        url,
                                                        '',
                                                        defLength,
                                                        0,
                                                        0);
        }
    }