gDig

local config = {}
config.itemFuel = 80
config.fuelSlot = 16

local data = {}
data.distance = 0
data.fuelBuff = 0

function reloadFuelBuff()
  data.fuelBuff = turtle.getItemCount()*config.itemFuel
end

function checkInv()
  return turtle.getItemCount(16) > 0
end

function checkFuel()
  if(turtle.getFuelLevel() < 10) then
    turtle.refuel(1)
    reloadFuelBuff()
  end
  return turtle.getFuelLevel()+data.fuelBuff > data.distance+5
end

function goForward(i)
  if(not turtle.forward()) then
    if(t>=5) then error("Immovable Object") end
    turtle.dig()
    goForward(i and i+1 or 1)
  end
end

function finish()
  turtle.turnLeft()
  turtle.turnLeft()
  for i = 1,data.distance do
    goForward()
  end
end

function digLoop()
    goForward()
    turtle.digDown()
    turtle.digUp()
end

function init()
    reloadFuelBuff()
    while checkFuel() and checkInv() do
        digLoop()
    end
    finish()
end
print("Ready? Put fuel in the active slot")
read()
init()