Ancient Debris Tunnel (AI Slop)

local args = { ... }
local length      = tonumber(args[1])
local num_tunnels = tonumber(args[2]) or 1
local spacing     = tonumber(args[3]) or 3

if not length or length < 1 or num_tunnels < 1 then
  print("Usage: tunnel_ancient <length> [num_tunnels=1] [spacing=3]")
  return
end

local ANCIENT = "minecraft:ancient_debris"
local LAVA    = "minecraft:lava"
local NETH    = "minecraft:netherrack"

local MIN_FUEL = 200

local nethSlot = nil
local fuelSlots = {}

-- -------- inventory / fuel --------

local function fuelLevel()
  local f = turtle.getFuelLevel()
  return type(f) == "string" and math.huge or f
end

local function isFuel()
  return turtle.refuel(0)
end

local function rescanInventory()
  fuelSlots = {}
  nethSlot = nil

  for i = 1, 16 do
    local d = turtle.getItemDetail(i)
    if d then
      if d.name == ANCIENT then
        -- keep
      elseif d.name == NETH then
        if not nethSlot then
          nethSlot = i
        else
          turtle.select(i)
          turtle.drop()
        end
      else
        turtle.select(i)
        if isFuel() then
          fuelSlots[#fuelSlots + 1] = i
        else
          turtle.drop()
        end
      end
    end
  end
  turtle.select(1)
end

local function refuelFast()
  if fuelLevel() >= MIN_FUEL then return end
  for _, s in ipairs(fuelSlots) do
    if turtle.getItemCount(s) > 0 then
      turtle.select(s)
      turtle.refuel()
      if fuelLevel() >= MIN_FUEL then break end
    end
  end
  turtle.select(1)
end

local function selectNeth()
  if nethSlot and turtle.getItemCount(nethSlot) > 0 then
    turtle.select(nethSlot)
    return true
  end
  for i = 1, 16 do
    local d = turtle.getItemDetail(i)
    if d and d.name == NETH and turtle.getItemCount(i) > 0 then
      nethSlot = i
      turtle.select(i)
      return true
    end
  end
  return false
end

-- -------- two core ops --------

-- navigate: dig solids (gravel-safe) then move. ignores liquids.
local function navigate(detectFn, digFn, moveFn, attackFn)
  while detectFn() do
    digFn()
  end
  while not moveFn() do
    if attackFn then attackFn() end
  end
end

-- check: if air -> place neth; if lava -> place neth; if ancient -> dig then place neth
local function check(inspectFn, digFn, placeFn)
  local ok, b = inspectFn()

  -- No block (air): fill it to make walkable/sealed
  if not ok then
    if selectNeth() then
      placeFn()
      turtle.select(1)
    end
    return
  end

  if not b then return end

  if b.name == ANCIENT then
    digFn()
    if selectNeth() then
      placeFn()
      turtle.select(1)
    end
  elseif b.name == LAVA then
    if selectNeth() then
      placeFn()
      turtle.select(1)
    end
  end
end

-- -------- directional wrappers --------

local function navigateForward() navigate(turtle.detect, turtle.dig, turtle.forward, turtle.attack) end
local function navigateUp()      navigate(turtle.detectUp, turtle.digUp, turtle.up, turtle.attackUp) end
local function navigateDown()    navigate(turtle.detectDown, turtle.digDown, turtle.down, turtle.attackDown) end

local function checkForward() check(turtle.inspect, turtle.dig, turtle.place) end
local function checkUp()      check(turtle.inspectUp, turtle.digUp, turtle.placeUp) end
local function checkDown()    check(turtle.inspectDown, turtle.digDown, turtle.placeDown) end

-- -------- tunnel dig --------

local function digTunnel(len)
  local upper = false

  for i = 1, len do
    refuelFast()

    -- move
    navigateForward()

    -- walls at current height
    turtle.turnLeft();  checkForward()
    turtle.turnRight(); turtle.turnRight(); checkForward()
    turtle.turnLeft()

    -- seal relevant walk surface at current height
    if upper then
      checkUp()     -- ceiling
    else
      checkDown()   -- floor
    end

    -- transition + walls + surface at new height
    if upper then
      navigateDown()
      upper = false

      turtle.turnLeft();  checkForward()
      turtle.turnRight(); turtle.turnRight(); checkForward()
      turtle.turnLeft()

      checkDown()
    else
      navigateUp()
      upper = true

      turtle.turnLeft();  checkForward()
      turtle.turnRight(); turtle.turnRight(); checkForward()
      turtle.turnLeft()

      checkUp()
    end

    if (i % 10) == 0 then rescanInventory() end
  end

  -- normalize to lower
  if upper then
    navigateDown()
  end
end

-- -------- main --------

rescanInventory()

for t = 1, num_tunnels do
  digTunnel(length)

  if t < num_tunnels then
    -- return to tunnel origin
    turtle.turnRight(); turtle.turnRight()
    for _ = 1, length do turtle.forward() end
    turtle.turnRight(); turtle.turnRight()

    -- shift right to next tunnel start
    turtle.turnRight()
    for _ = 1, spacing do navigateForward() end
    turtle.turnLeft()
  end
end

-- return to absolute start
turtle.turnRight(); turtle.turnRight()
for _ = 1, length do turtle.forward() end
turtle.turnRight(); turtle.turnRight()

if num_tunnels > 1 then
  turtle.turnLeft()
  for _ = 1, spacing * (num_tunnels - 1) do navigateForward() end
  turtle.turnRight()
end

print("Done. Returned to start.")