var MenuSpeed = 9;
var MenuTimer = 15;
var MenuOpacity = 0.8;

// main function to handle the mouse events //
function Menu(id, inside) {
    var h = document.getElementById(id + '-ddheader');
    var c = document.getElementById(id + '-ddcontent');

    clearInterval(c.timer);

    if (inside) {
        clearTimeout(h.timer);
        if (c.maxh && c.maxh <= c.offsetHeight) {
            return
        }
        else if (!c.maxh) {
            c.style.display = 'block';
            c.style.height = 'auto';
            c.maxh = c.offsetHeight;
            c.style.height = '1px';
        }
        c.timer = setInterval(function () { MenuSlide(c, 1) }, MenuTimer);
    }
    else {
        h.style.backgroundColor = "";
        h.timer = setTimeout(function () { MenuCollapse(c) }, 50);
    }
}

// collapse the menu //
function MenuCollapse(c) {
    c.timer = setInterval(function () { MenuSlide(c, -1) }, MenuTimer);
}

// cancel the collapse if a user rolls over the dropdown //
function MenuCancelHide(id) {
    var h = document.getElementById(id + '-ddheader');
    var c = document.getElementById(id + '-ddcontent');
    clearTimeout(h.timer);
    clearInterval(c.timer);
    if (c.offsetHeight < c.maxh) {
        c.timer = setInterval(function () { MenuSlide(c, 1) }, MenuTimer);
    }
}

// incrementally expand/contract the dropdown and change the opacity //
function MenuSlide(c, d) {
    var currh = c.offsetHeight;
    var dist;

    if (d == 1) {
        dist = (Math.round((c.maxh - currh) / MenuSpeed));
    }
    else {
        dist = (Math.round(currh / MenuSpeed));
    }

    if (dist <= 1 && d == 1) {
        dist = 1;
    }

    c.style.height = '' + (currh + (dist * d)) + 'px';
    MenuSetOpacity(c, MenuOpacity * currh / c.maxh);

    if ((currh < 2 && d != 1) || (currh > (c.maxh - 2) && d == 1)) {
        clearInterval(c.timer);
    }
}

function MenuSetOpacity(item, opacity) {
    item.style.opacity = opacity;
    item.style.filter = 'alpha(opacity=' + opacity * 100 + ')';
}