Tunnel 3byX

--[[
  pastebin get xp6cFAP8 tunnel
  Tunnel 3x3 program by reaperDG
  Dat 'FAP' in url...
--]]

local arg = {...}
local length = arg[1]
local fuel = turtle.getFuelLevel()
local reqFuel = length*5

-- Checks if there is block in front of turtle (It can even dig column of gravel!)
function checkDig()
  while true do
    if turtle.detect() then
      turtle.dig()
    else
      break
    end
  end
end

-- Sequence of digging 3x1
function sequence()
  turtle.digUp()
  turtle.up()
  turtle.turnLeft()
  turtle.dig()
  turtle.turnRight()
  turtle.turnRight()
  turtle.dig()
  turtle.turnLeft()
end

-- Checks if there is enough fuel to dig this tunnel
if fuel < reqFuel then
  print("Too low on fuel do do this!")
  print("I need "..reqFuel.." fuel do dig this tunnel!")
  error()
end

-- If there is no block in front of turtle then go forward

while true do
  if not turtle.detect() then
    turtle.forward()
  else
    break
  end
end

-- Main loop for digging tunnel
for i=1,length do
  checkDig()
  turtle.forward()
  turtle.turnLeft()
  checkDig()
  turtle.turnRight()
  turtle.turnRight()
  checkDig()
  turtle.turnLeft()
  sequence()
  sequence()
  turtle.down()
  turtle.down()
end

-- End message
print("Done!")