Turtle cuboid

local tArgs = { ... }
if #tArgs ~= 3 then
  print("Usage: cuboid <length> <breadth> <height>")
end
local l,b,h
l=tArgs[1]
b=tArgs[2]
h=tArgs[3]
print("Digging "..l.."x"..b.."x"..h.." ...")
local shouldTurnRight = true;

function checkFuel()
  local printed = false
  while true do
    if(turtle.getFuelLevel() > 0) then
      return
    else
      for k=1,16 do
        turtle.select(k)
        if(turtle.refuel()) then
          print("refuelling ...")
          return
        end
      end
      if(not printed) then
        print("Fuel needed")
        printed = true
      end
      sleep(5)
    end
  end
end


local function goForward(n)
  for i=1,n do
    checkFuel()
    while true do
      turtle.dig()
      if turtle.forward() then
        break
      end
    end
  end
  return
end

local function stepDown()
  checkFuel()
  while true do
    turtle.digDown()
    if turtle.down() then
      break
    end
  end
end

for j=1,h do
  for i=1,b-1 do
    goForward(l-1)
    if(shouldTurnRight) then
      turtle.turnRight()
      shouldTurnRight = false
      goForward(1)
      turtle.turnRight()
    else
      turtle.turnLeft()
      shouldTurnRight = true
      goForward(1)
      turtle.turnLeft()
    end
  end
  goForward(l-1)
  if j<tonumber(h) then
    turtle.turnLeft()
    turtle.turnLeft()
    stepDown()
  end
end