var DDSPEED = 5;
var DDTIMER = 15;

// main function to handle the mouse events //
function ddMenu(id, d) {
    var h = document.getElementById(id + '-ddheader');
    var c = document.getElementById(id + '-ddcontent');
    clearInterval(c.timer);
    if (d == 1) {
        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 = '0px';
        }
        c.timer = setInterval(function() { ddSlide(c, 1) }, DDTIMER);
    } else {
        h.timer = setTimeout(function() { ddCollapse(c) }, 50);
    }
}

// collapse the menu //
function ddCollapse(c) {
    c.timer = setInterval(function() { ddSlide(c, -1) }, DDTIMER);
}

// cancel the collapse if a user rolls over the dropdown //
function cancelHide(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() { ddSlide(c, 1) }, DDTIMER);
    }
}

// incrementally expand/contract the dropdown and change the opacity //
function ddSlide(c, d) {
    var currh = c.offsetHeight;
    var dist;
    if (d == 1) {
        dist = (Math.round((c.maxh - currh) / DDSPEED));
    } else {
        dist = (Math.round(currh / DDSPEED));
    }
    if (dist <= 1 && d == 1) {
        dist = 1;
    }
    c.style.height = currh + (dist * d) + 'px';
    c.style.opacity = currh / c.maxh;
    c.style.filter = 'alpha(opacity=' + (currh * 100 / c.maxh) + ')';
    if ((currh < 2 && d != 1) || (currh > (c.maxh - 2) && d == 1)) {
        clearInterval(c.timer);
    }
}