Radio controller

local args = {...}
local side = "top"

if not args[1] then
    local str = "OFF"
    local vol = redstone.getAnalogOutput(side)

    if vol ~= 0 then str = "ON" end

    print("Radio is currently "..str..".")
    print("Volume is "..vol.." / 15.")
    print("\n")
    print("Usage: radio < on / off / volume >")
    print("Volume can be an integer from 1 to 15. Use 0 to turn off the radio.")
    return
end

if args[1] == "on" then
    if redstone.getAnalogOutput(side) ~= 0 then
        print("The radio is already on.")
    end

    io.write("What volume? (1 - 15): ")
    local vol = io.read()

    os.run({}, shell.getRunningProgram(), vol)

    return
elseif args[1] == "off" then
    redstone.setAnalogOutput(side,0)
    print("Turning radio off. Goodbye!")
    return
else
  local vol = tonumber(args[1])

  if not vol or vol ~= math.floor(vol) then
      print("Please provide an integer.")
      return
  end

  vol = math.floor(vol)

  if vol < 1 then
      os.run({}, shell.getRunningProgram(), "off")
      return
  end

  if vol > 15 then
      print("Volume is out of range. Please provide an integer below 16.")
      return
  end

  print("Setting volume to "..vol.." / 15.")
  redstone.setAnalogOutput(side, vol)
end