Ceiling

params = {...}
-- The input is text so we convert the text to a number.
floorLength = tonumber(params[1])
floorWidth = tonumber(params[2])

currentSlot = 1

-- This variable is used to alternate which way we are turning.
turnRight = true

function gotoNextSlotIfEmpty()
  if turtle.getItemCount(currentSlot) == 0 then
    currentSlot = currentSlot + 1
    turtle.select(currentSlot)
  end
end

function refuel()
fuel = turtle.getFuelLevel()
if fuel < 5 then
        turtle.select(16)
        turtle.refuel(1)
        turtle.select(currentSlot)
    end
end

turtle.select(currentSlot)
-- turtle.up()

for width = 1, floorWidth do

  for length = 1, floorLength do

    refuel()
    turtle.placeUp()
    gotoNextSlotIfEmpty()
    if length ~= floorLength then
      turtle.forward()
    end

  end

  -- When you get to the end of a row of blocks you need to turn around and setup for the next row,
  -- but every time you turn around you need to alternate the way that you turn.
  -- If this is confusing try drawing it out on a peice of paper.
  if turnRight then
    turtle.turnRight()
    turtle.forward()
    turtle.turnRight()
  else
    turtle.turnLeft()
    turtle.forward()
    turtle.turnLeft()
  end

  -- Change so that we turn the other way next time.
  turnRight = not turnRight
end