pillar

local deep = 0
local fuelNeeded = deep
local tArgs = { ... }
function surface()
  while deep > 0 do
    if turtle.up() then
      deep = deep - 1
      for i=2,16 do
        if turtle.getItemCount(i) > 0 then
          turtle.select(i)
          local aok = true
          local b = 0
          while aok do
            if turtle.placeDown() then
              aok = false
            else
              b =b + 1
            end
            if b > 50 then
              aok = false
            end
          end
          break
        end
      end
      turtle.select(1)

    else
      local bm = 0
      while turtle.getFuelLevel < 80 do
        print("Turtle is refueling...")
        turtle.select(1)
        turtle.refuel(1)
        bm = bm + 1
        if bm > 10 then
          break
        end
      end
    end
  end
end

function dig()
  if turtle.digDown() then
    if not turtle.down() then
      local t = false
      for i=0,40 do
        if turtle.down() then
          t = true
          break
        end
      end
      if not t then
        print("Turtle is stuck...")
        return
      end
    end
  end
end

function run(limit)
  local ok = true
  while ok do
    fuelNeeded = deep
    fuelNeeded = fuelNeeded + 80
    if turtle.getFuelLevel() < fuelNeeded then
      turtle.select(1)
      if turtle.getItemCount(1) > 0 then
        turtle.refuel(1)
      else
        surface()
        ok = false
        error("Ran short of fuel")
      end
    else
      if deep > tonumber(limit) then
        ok = false
        surface()
      else
        dig()
      end
    end
  end
end

if #tArgs > 0 then
  run(tonumber(tArgs[0]))
else
  run(256)
end