Calculate 8-axis movement angle with LÖVE and ammo-input

gistfile1.lua

-- returns nil if there's no movement
function getDirection()
  local xAxis = input.axisDown("left", "right")
  local yAxis = input.axisDown("up", "down")
  local xAngle = xAxis == 1 and 0 or (xAxis == -1 and math.tau / 2 or nil)
  local yAngle = yAxis == 1 and math.tau / 4 or (yAxis == -1 and math.tau * 0.75 or nil)

  if xAngle and yAngle then
    -- x = 1, y = -1 is a special case the doesn't fit; not sure what I can do about it other than this:
    if xAxis == 1 and yAxis == -1 then return yAngle + math.tau / 8 end
    return (xAngle + yAngle) / 2
  else
    return xAngle or yAngle
  end
end