felling turtle 2x2 logging turtle

-- Author: ArbitraryHubris
-- place saplings in slot 1, bone meal in slot 2

unknown, saplings = 0, 1

local function plantSaplings()
  -- clear and plant logs in 2x2 layout and return to starting position
  print("Planting saplings")
  turtle.select(1)
  turtle.dig()
  turtle.forward()
  turtle.dig()
  turtle.forward()
  turtle.turnRight()
  turtle.dig()
  turtle.place()
  turtle.turnLeft()
  turtle.back()
  turtle.place()
  turtle.turnRight()
  turtle.dig()
  turtle.place()
  turtle.turnLeft()
  turtle.back()
  turtle.place()
  turtle.select(2)
  turtle.place()
  print("Saplings planted")
end


local function detectItem()
  turtle.select(saplings)
  if turtle.compare() then
    -- print("Detected sapling")
    return saplings
  end
  return unknown
end


local function fell()
  height = 0
  turtle.dig()
  turtle.forward()
  while turtle.detectUp() do
    height = height + 1
    turtle.digUp()
    turtle.dig()
    turtle.up()
  end
  turtle.turnRight()
  turtle.dig()
  turtle.forward()
  turtle.turnLeft()
  while height > 0 do
    turtle.dig()
    turtle.digDown()
    turtle.down()
    height = height - 1
  end
  turtle.down()
  turtle.dig()
  turtle.turnLeft()
  turtle.forward()
  turtle.turnLeft()
  turtle.forward()
  for i = 3,16 do
    turtle.select(i)
    turtle.drop()
  end
  turtle.turnLeft()
  turtle.turnLeft()
end


local function waitForTree()
  seconds = 0
  while true do
    print("Waiting for sapling to grow for " .. seconds .. " seconds")
    os.sleep(10)
    seconds = seconds + 10
    if detectItem() ~= saplings then
      return
    end
  end
end


while true do
  plantSaplings()
  waitForTree()
  fell()
end