Tunnel Program

function placeFloorBlock()
  if not turtle.detectDown() then
    turtle.select(3)
    if turtle.placeDown() then
      return true
    end
    print("Placing floor failed")
    return false
  end
end

function fuel()
  if turtle.getFuelLevel() < 25 then
    turtle.select(1)
    if turtle.refuel(1) then
      return true
    end
    print ("Refuelling failed")
    return false
  end
end

function DigAndMove()
  while not turtle.forward() do
    if not turtle.dig() then
      turtle.attack()
    end
  end
  while turtle.detectUp() do
    turtle.digUp()
    sleep(0.5)
  end
  placeFloorBlock()
end

function turnAround()
  turtle.turnLeft()
  turtle.turnLeft()
end

function placeTorch()
  turtle.turnRight()
  turtle.dig()
  if not turtle.detect() then
    turtle.select(2)
    if turtle.place() then
      turtle.turnLeft()
      return true
    end
  end
  print("Place torch failed")
  turtle.turnLeft()
  return false
end

local tArgs = { ... }
local length = tonumber(tArgs[1])
local moveBack = 0

local blocksMovedForward = 0
while blocksMovedForward < length do
  fuel()
  DigAndMove()
  blocksMovedForward = blocksMovedForward + 1

  -- add torches
  if (blocksMovedForward % 8) == 0 then
    placeTorch()
  end

  if blocksMovedForward == length then
    turnAround()
    while moveBack < length do
      fuel()
      turtle.forward()
      moveBack = moveBack + 1
    end
  end
end

turnAround()