T2

-- Variables --
fuel = 64
length = 4
rows = 4
sapling = 1
-- End Variables --


-- Functions --
function fuel() -- Let's the turtle refuel itself.
  if turtle.getFuelLevel() < 30 then
     turtle.select(16)
     turtle.refuel(fuel)
     turtle.select(sapling)
  else
     os.sleep(0.1)
  end
end

function move() -- Handles the turtle's movement function.
  for i=1, length do
     turtle.forward()
     checktree()
  end
end

function navL() -- Navigates left.
  turtle.turnLeft()
  turtle.forward()
  turtle.forward()
  turtle.turnLeft()
  turtle.placeDown()
end

function navR() -- Navigates right.
  turtle.turnRight()
  turtle.forward()
  turtle.forward()
  turtle.turnRight()
  turtle.placeDown()
end

function log() -- Initiates the loggingturtle.
  for i=1, rows do
    move()
    navL()
    move()
    navR()
  end
end

function scanlog() -- Scans for logs above turtle
  if turtle.detectUp() == true then
     while turtle.detectUp() == true do
       turtle.digUp()
       turtle.up()
     end
  else turtle.forward()
  end
end

function descend() -- Let's the turtle descend properly
  while turtle.detectDown() ~= true do
     turtle.down()
     turtle.select(sapling)
     turtle.placeDown()
  end
end

function checktree() -- Scans block in front, if it detects anything it breaks the block, otherwise move forward and try to place sapling
  if turtle.detect() == true then
     turtle.dig()
     turtle.forward()
     turtle.digDown()
     scanlog()
     descend()
  else
     turtle.forward()
     turtle.select(sapling)
     turtle.placeDown()
  end
end
-- End Functions --

-- Execute code below this line --
log()