y = 0

mineUp = function()
  while(turtle.detectUp()) do
    ensureFuel()
    turtle.digUp()
    turtle.dig()
    turtle.up()
    y = y+1
  end
end
  
mineDown = function()
  while(y > 0) do
    ensureFuel()
    if(not turtle.down()) then
      turtle.digDown()
      turtle.dig()
      mineDown()
    else
      y = y-1
    end    
  end
end

ensureFuel = function()
  if(turtle.getFuelLevel() < y) then
    for iter = 1, 16, 1 do
      if(turtle.getFuelLevel() < y) then
        turtle.select(iter)
        turtle.refuel(y)
      end
    end
  end
end

--[[
turtle.dig()
turtle.forward()
mineUp()
turtle.dig()
turtle.forward()
mineDown()
turtle.turnLeft()
turtle.dig()
turtle.forward()
mineUp()
turtle.turnLeft()
turtle.dig()
turtle.forward()
mineDown()
print("Done.")
]]--

turtle.dig()
turtle.forward()
mineUp()
turtle.turnLeft()
turtle.dig()
turtle.forward()
turtle.turnRight()
mineDown()
turtle.dig()
print("Done.")
