Swap unit with mouse wheel in Istrolid

SwapUnit.js

var scrollunit = {};

scrollunit.draw = buildBar.draw;
scrollunit.slotFleet = [6, 6, 4, 4, 7, 2, 3, 5, 5, 1];
scrollunit.slotIndex = [];

scrollunit.findUnitIndex = function(spec, fleet) {
    for(var i = 0; i < 10; i++) {
        if(commander.fleet[fleet + "," + i] === spec) {
            return i;
        }
    }
    return -1;
}

scrollunit.getBtnIndex = function(btn) {
    if (!btn || btn.style.position !== "absolute") return -1;
    var i = 0;
    while (btn = btn.previousElementSibling) {
        i++;
    }
    return i;
}

buildBar.draw = function(folded) {
    var ret = scrollunit.draw.call(this, folded);

    var btns = document.getElementsByClassName("unitpic");

    for(var i in btns) {
        if(btns[i].style && btns[i].style.position !== "absolute") continue;

        btns[i].onwheel = function(e) {
            var index = scrollunit.getBtnIndex(this);

            if(commander.fleet.selection.row === 0 && commander.fleet.selection.tab === "default" &&
                scrollunit.slotFleet[index] > 0) {
                e.stopPropagation();
                if(scrollunit.slotIndex[index] == undefined) {
                    scrollunit.slotIndex[index] = scrollunit.findUnitIndex(
                        commander.buildBar[index],
                        scrollunit.slotFleet[index]);
                }

                var ind = scrollunit.slotIndex[index];

                do {
                    ind -= Math.sign(e.deltaY);
                    if(ind > 9)
                        ind = 0;
                    else if(ind < 0)
                        ind = 9;
                } while(ind != scrollunit.slotIndex[index] &&
                    buildBar.emptySpec(commander.fleet[
                        scrollunit.slotFleet[index] + "," + ind]));

                buildBar.setSpec(index, commander.fleet[
                    scrollunit.slotFleet[index] + "," + ind]);

                scrollunit.slotIndex[index] = ind;

                onecup.refresh();
                account.save();

                e.preventDefault();
            }
        }
    }

    return ret;
}