Minecraft Turtle 3x3 Tunnel

local inputs = {...}
local depth = inputs[1] or 1
local depthwent = 0
function mine()
  turtle.dig()
  turtle.up()
  turtle.dig()
  turtle.up()
  turtle.dig()
  turtle.turnRight()
  turtle.forward()
  turtle.turnLeft()
  turtle.dig()
  turtle.down()
  turtle.dig()
  turtle.down()
  turtle.dig()
  turtle.turnRight()
  turtle.forward()
  turtle.turnLeft()
  turtle.dig()
  turtle.up()
  turtle.dig()
  turtle.up()
  turtle.dig()
  turtle.forward()
  turtle.dig()
  turtle.down()
  turtle.dig()
  turtle.down()
  turtle.dig()
  turtle.turnLeft()
  turtle.forward()
  turtle.turnRight()
  turtle.dig()
  turtle.up()
  turtle.dig()
  turtle.up()
  turtle.dig()
  turtle.turnLeft()
  turtle.forward()
  turtle.turnRight()
  turtle.dig()
  turtle.down()
  turtle.dig()
  turtle.down()
  turtle.dig()
  turtle.forward()
  depthwent=depthwent+2
  if isfull() then
    home()
    dump()
    back()
  end
end

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

function home()
  for i=1,depthwent*2 do
    turtle.back()
  end
end

function back()
  for i=1,depthwent*2 do
    turtle.forward()
  end
end

function dump()
  turtle.turnRight()
  turtle.turnRight()
  for i=1,16 do
    turtle.select(i)
    turtle.drop()
  end
  turtle.select(1)
  turtle.turnRight()
  turtle.turnRight()
end

turtle.select(1)
for i=1,depth do
  mine()
end

home()
dump()