ShaftMaker

function mineForward(times)
   for i = 1, times do
      while not turtle.forward() do
         turtle.dig()
      end
   end
end

function mineDown()
   while not turtle.down() do
      turtle.digDown()
   end
end

function mineUp()
   while not turtle.up() do
      turtle.digUp()
   end
end

function turn180()
   turtle.turnRight()
   turtle.turnRight()
end

function placeSides()
   turtle.turnRight()
   turtle.place()
   turn180()
   turtle.place()
   turtle.turnRight()
end

function checkFuel(spaces)
   local maxSpaces = spaces + 4
   if turtle.getFuelLevel() ~= "unlimited" and turtle.getFuelLevel() <= maxSpaces then
      print("Refueling...")
      refuel()
      if turtle.getFuelLevel() <= maxSpaces then
         turn180()
         print("NO MORE FUEL, RETURNING HOME")
         mineForward(spaces)
      end
   end
end

function refuel()
   local i = 1
   while i <= 16 and not turtle.refuel(1) do
      i = i + 1
      turtle.select(i)
   end
   turtle.select(1)
end


term.write("Enter distance:")
local d = tonumber(read())

for i = 1, d do
   mineForward(1)
   turtle.placeUp()
   placeSides()

   mineDown()
   turtle.placeDown()
   placeSides()

   mineForward(1)
   turtle.placeDown()
   placeSides()

   mineUp()
   turtle.placeUp()
   placeSides()

   checkFuel(i)
end
print("Finished!")