ComputerCraft lzChop

local saplingSlot = 15
local boneMealSlot = 16

local bone, chop, empty, plant, wait, waitForKey, watch

bone = function()
    turtle.select(saplingSlot)

    while turtle.getItemCount(boneMealSlot) > 1 and turtle.compare() do
        turtle.select(boneMealSlot)
        turtle.place()
        turtle.select(saplingSlot)
    end
end

chop = function()
    local height = 1
    local downSteps = 1

    turtle.select(1)
    turtle.dig()
    turtle.forward()

    while turtle.compareUp() do
        turtle.digUp()
        turtle.up()

        height = height + 1
    end

    for i = 1, height - 1 do
        turtle.down()
    end

    turtle.back()
end

empty = function()
    for slot = 1, 14 do
        if turtle.getItemCount(slot) > 0 then
            turtle.select(slot)
            turtle.dropUp()
        end
    end
end

plant = function()
    turtle.select(saplingSlot)

    while true do
        turtle.dropDown()
        turtle.suckDown()

        if turtle.getItemCount(saplingSlot) > 1 then
            break
        end

        wait(60)
    end

    if not turtle.place() then
        print 'Obstacle in front of Turtle or no ground to plant on'
        waitForKey(keys.enter)
    end
end

wait = function(seconds)
    seconds = seconds or 1

    local timerId = os.startTimer(seconds)

    local _, id

    repeat
        _, id = os.pullEvent 'timer'
    until id == timerId
end

waitForKey = function(key)
    local _, keyPressed

    repeat
        _, keyPressed = os.pullEvent 'key'

    until keyPressed == key
end

watch = function()
    turtle.select(saplingSlot)

    while turtle.compare() do
        wait(1)
    end
end

-- Main loop
(function()
    print('Saplings in slot ', saplingSlot)
    print('Bone Meal in slot ', boneMealSlot)

    print 'Logs are output to top face'
    print 'Saplings are input from bottom face'
    print 'Press Enter when ready'

    waitForKey(keys.enter)

    while true do
        plant()
        bone()
        watch()
        chop()
        empty()
    end
end)()