local usbWatcher = nil

function usbDeviceCallback(data)
    -- 4176/1031 is Yubico/Yubikey4
    if (data["vendorID"] == 4176 and data["productID"] == 1031) then
        if (data["eventType"] == "added") then
            hs.caffeinate.set("displayIdle", false, false)
        elseif (data["eventType"] == "removed") then
            hs.caffeinate.set("displayIdle", true, false)
            hs.caffeinate.startScreensaver()
        end
    end
end

usbWatcher = hs.usb.watcher.new(usbDeviceCallback)
usbWatcher:start()