SAFE_SLOTS = 1
LAST_FILLER_SLOT = 8
SLOT_COUNT = 16

function selectFiller()
  for slot = SAFE_SLOTS + 1, SLOT_COUNT do
    turtle.select(slot)
    if turtle.compareTo(2) and turtle.getItemCount() > 1 then
      return
    end
  end
end

function placeFiller(direction)
  if direction == nil then
    direction = ''
  end

  while turtle['detect' .. direction]() do
    turtle['dig' .. direction]()
  end
  selectFiller()
  turtle['place' .. direction]()
end

function clear(direction)
  if direction == nil then
    direction = ''
  end

  while turtle['detect' .. direction]() do
    selectFiller()
    turtle['place' .. direction]()
    turtle['dig' .. direction]()
  end
end

function move(direction)
  clear(direction)

  if direction == nil or direction == '' then
    turtle.forward()
  elseif direction == 'Up' then
    turtle.up()
  else
    turtle.down()
  end
end

function dropNonFuel()
  for slot = LAST_FILLER_SLOT + 1, SLOT_COUNT do
    turtle.select(slot)
    if not turtle.refuel() then
      turtle.drop()
    end
  end
end

function buildLayer(width, height)
  direction = 'Right'
  for x = 1, width do
    for y = 1, height - 1 do
      clear('Down')
      move()
    end
    clear('Down')
    turtle['turn' .. direction]()
    move()
    turtle['turn' .. direction]()
    if direction == 'Right' then
      direction = 'Left'
    else
      direction = 'Right'
    end
  end

  if direction == 'Left' then
    turtle.turnRight()
    move()
    turtle.turnLeft()
  else
    turtle.turnLeft()
    move()
    turtle.turnRight()
  end

  move('Down')

  dropNonFuel()
end

turtle.turnLeft()
turtle.forward()
turtle.forward()
turtle.turnLeft()
turtle.forward()
turtle.forward()
turtle.turnLeft()
turtle.turnLeft()

for i = 1,45 do
  buildLayer(5, 5)
end