[CC-Turtle] 4x2x2-Fir/Redwood-Farm

local height = 0
local time = os.clock()
local fuelNeeded = false

local function forward()
  while not turtle.forward() do
    turtle.attack()
    turtle.dig()
  end
  return true
end

local function down()
  while not turtle.down() do
    turtle.attackDown()
    turtle.digDown()
  end
  return true
end

local function up()
  while not turtle.up() do
    turtle.attackUp()
    turtle.digUp()
  end
  return true
end

local function checkFuel()
  if turtle.getFuelLevel() <= 200 then
    fuelNeeded = true
  elseif turtle.getFuelLevel() <= 10 then
    error("Bitte manuel auftanken.")
  else
    fuelNeeded = false
  end
end

local function checkSuck()
  if os.clock() >= (time + 200) then
    down()
    down()
    time = os.clock()
    turtle.suckDown()
    up()
    up()
  end
end

local function checkSlots(sCount)
  if turtle.getItemCount(1) < sCount then
    print("Zu wenige Saplings in Slot 1, bitte mindestens ", sCount, " einfuellen und Taste druecken.")
    os.pullEvent("key")
  end
end

local function drop()
  down()
  down()
  down()
  for i=2, 16 do
    turtle.select(i)
    turtle.dropDown()
  end
  turtle.select(1)
  up()
  turtle.suckDown()
  time = os.clock()
  up()
  up()
  checkFuel()
end

local function harvest()
  checkSlots(5)
  turtle.select(2)
  turtle.down()
  turtle.dig()
  forward()
  while turtle.detectUp() do
    turtle.dig()
    turtle.digUp()
    if up() then
      height = height + 1
    end
  end
  turtle.dig()
  turtle.turnLeft()
  turtle.dig()
  forward()
  turtle.turnRight()
  while height > 0 do
    turtle.dig()
    turtle.digDown()
    if down() then
      height = height - 1
    end
  end
  turtle.dig()
  checkSlots(5)
  turtle.select(1)
  turtle.dig()
  turtle.place()
  turtle.turnRight()
  forward()
  turtle.turnLeft()
  turtle.dig()
  turtle.place()
  turtle.turnLeft()
  turtle.place()
  turtle.turnLeft()
  forward()
  turtle.turnLeft()
  turtle.turnLeft()
  turtle.place()
  checkFuel()
  if fuelNeeded then
    for i=2, 16 do
    turtle.select(i)
    turtle.refuel()
    end
    turtle.select(1)
    checkFuel()
  end
  up()
  drop()
end

local function place()
  checkSlots(5)
  turtle.select(1)
  forward()
  turtle.turnLeft()
  forward()
  turtle.turnRight()
  turtle.dig()
  turtle.place()
  turtle.turnRight()
  forward()
  turtle.turnLeft()
  turtle.dig()
  turtle.place()
  turtle.turnLeft()
  turtle.place()
  turtle.turnLeft()
  forward()
  turtle.turnLeft()
  turtle.turnLeft()
  turtle.place()
end

local function start()
  checkSlots(17)
  checkSuck()
  checkFuel()
  for i = 1, 4 do
    place()
    turtle.turnLeft()
  end
  up()
  checkFuel()
end

local function wait()
  checkSlots(5)
  select(1)
  while not turtle.detect() do
    turtle.turnLeft()
    sleep(1)
    checkSuck()
  end
end

----------------------------------------------

start()
while true do
  wait()
  harvest()
end