MineshaftTurtle

level=0

function addFuel()
  for i=1, level, 1 do
    turtle.up()
  end

  turtle.turnLeft()
  turtle.turnLeft()

  dumpInventory()

  turtle.turnRight()

  turtle.select(1)
  turtle.suck()

  turtle.select(3)
  turtle.drop()

  turtle.turnRight()

  for i=0, level, 1 do
    turtle.down()
  end
end

function Refuel()
  fuelLevel = turtle.getFuelLevel()

  if fuelLevel <= 9 then
    turtle.select(1)
    turtle.refuel(1)
  end

  if turtle.getItemCount(1) <=5 then
    addFuel()
  end
end

function digLayer()
  turtle.digDown()
  turtle.suckDown()
  turtle.down()
  turtle.dig()
  turtle.forward()
  turtle.dig()
  turtle.forward()

  turtle.turnRight()

  turtle.dig()
  turtle.forward()
  turtle.turnRight()
  turtle.dig()
  turtle.forward()
  turtle.dig()
  turtle.forward()

  turtle.turnLeft()

  turtle.dig()
  turtle.forward()

  turtle.turnLeft()
  turtle.dig()
  turtle.forward()
  turtle.dig()
  turtle.forward()
end

function placeLadder()
  turtle.back()
  turtle.turnLeft()
  turtle.forward()
  turtle.select(2)
  turtle.place()
end

function returnCorner()
  turtle.turnLeft()
  turtle.forward()
  turtle.turnRight()
  turtle.forward()
  turtle.turnRight()
end

function dumpInventory()
  for i=3, 16, 1 do
    turtle.select(i)
    turtle.drop()
  end

  turtle.select(1)
end

function surfaceReturn()
  for i=0, level, 1 do
    turtle.up()
  end

  turtle.turnLeft()
  turtle.turnLeft()

  dumpInventory()

  turtle.turnRight()
  turtle.turnRight()

  for i=0, level, 1 do
    turtle.down()
  end
end

function endShaft()
  for i=1,level,1 do
    turtle.up()
  end

  turtle.turnLeft()
  turtle.turnLeft()

  dumpInventory()

  turtle.turnLeft()
  turtle.turnLeft()
end

function checkInventory()
  invSpace = turtle.getItemCount(16)

  if invSpace ~= 0 then
    surfaceReturn()
  end
end

local tArgs = {...}

Refuel()

if #tArgs~=1 then
  print("Depth required")
end

for i=1, tArgs[1],1 do
  Refuel()
  digLayer()
  placeLadder()
  returnCorner()
  checkInventory()
  level=level+1
end

Refuel()
endShaft()