function updateLabel(label, tx, ty) {
    label.left += tx;
    label.cx += tx;
    label.right += tx;

    label.top += ty;
    label.cy += ty;
    label.bottom += ty;
}

function colision(a, b) {
    return a.left < b.right &&
        a.right > b.left &&
        a.top < b.bottom &&
        a.bottom > b.top;
}

// based on http://bl.ocks.org/larskotthoff/11406992
function arrangeLabels(labels, module, loops) {
    var move = true;

    module /= labels.length;

    while (move && loops--) {
        move = false;

        labels.forEach(function (a) {
            labels.forEach(function (b) {
                if (b !== a) {
                    if (colision(a, b)) {
                        move = true;
                        updateLabel(b, -module * Math.sign(a.cx - b.cx), -module * Math.sign(a.cy - b.cy));
                        updateLabel(a, module * Math.sign(a.cx - b.cx), module * Math.sign(a.cy - b.cy));
                    }
                }
            });
        });
    }
}

function addMargin(label, margin) {
    label.left -= margin;
    label.right += margin;
    label.top -= margin;
    label.bottom += margin;
    label.width += 2 * margin;
    label.height += 2 * margin;
}