wood

--Wood

--------------------
--| slot | item    |
---------+----------
--|  1   | gravel  |
--|  2   | wood    |
--|  3   | sand    |
--|  4   | stone   |
--|  5   | sapling |
--|  6   | slab    |
--|  16  | fuel    |
--------------------

turtle.select(4) --stone
if turtle.compareDown() then
  go()
  turtle.select(3) --sand
  if turtle.compareDown() then
    turtle.turnLeft()
    cut()
    plant()
    turtle.turnRight()
  else
    turtle.select(6) --slab
    if turtle.compareDown() then
      cut()
      plant()
      turtle.turnRight()
    else
      turtle.select(4) --stone
      if turtle.compareDown() then
        turtle.turnRight()
      end
    end
  end
end


function go() --avance
 print("going")
 turtle.select(1) --gravel
 turtle.forward()
 while turtle.compareDown() do
  turtle.forward()
 end
end

function plant()
 print("planting")
 if not turtle.detect() then
  turtle.select(5) --sapling
  turtle.place()
 end
end

function cut()
 print("cutting")
 turtle.select(2) --wood
 if turtle.compare() then
  turtle.dig()
  turtle.forward()
  while turtle.detectUp() do
   turtle.digUp()
   turtle.up()
  end
  while not turtle.detectDown() do
   turtle.down()
  end
  turtle.back()
 end
 if not turtle.detect() then
  plant()
 end
end