utils

gfl = turtle.getFuelLevel
local refuel(amount)
  local slot = turtle.select()
  if gfl() < amount) then
    for i = 1, 16 do
      while turtle.refuel() do
        if gfl() >= amount then
          turtle.select(slot)
          return true
        end
      end
    end
  end
  return false
end

local forward()
  while not turtle.forward do
    if not refuel(1) then
      os.sleep(10)
    end
  end
end

local back()
  while not turtle.back do
    os.sleep(10)

local tHandlers = {
  ["B"] = turtle.back,
  ["D"] = turtle.down,
  ["F"] = turtle.forward,
  ["L"] = turtle.turnLeft,
  ["O"] = turtle.placeUp,
  ["P"] = turtle.place,
  ["Q"] = turtle.placeDown,
  ["R"] = turtle.turnRight,
  ["U"] = turtle.up
}

local function exec(command)
  if type(command) ~= "string" then return end
  for i = 1, #command do
    local cmd = tHandlers[command:sub(i,i)]
    if cmd then cmd() end
  end
end

local function door(n)
  turtle.select(n)
  exec("BUQUQPLLPRBP")
end

local function wall(n)
  turtle.select(n)
  exec("BPLLPUQ PLLPUQ PLLPRBP")
end

local function corner(n)
  turtle.select(16)
  turtle.placeDown()
  turtle.select(n)
  exec("LFFRPDPDP")
end

local function ladder()
  turtle.select(15)
  exec("BLFDQUQUQUQRFF")
end

local function noladder()
  exec("UULFRF")
end

local function ceiling(n)
  turtle.select(n)
  exec("QBQBQBQRFR QBQBQBQLFL QBQBQBQRFR QBQBQBQ")
end

ceiling()
os.exit()

turtle.forward()
turtle.forward()
turtle.forward()
turtle.turnRight()
door()
corner()
wall()