Tree.lua

local treeSapling = "minecraft:spruce_sapling"
local logType = "minecraft:spruce_log"
local rows = tonumber(arg[1])
local currentRow = 1

local storeItems = {}

storeItems[logType] = true
storeItems["minecraft:stick"] = true

function selectItem(item)
    for i = 1, 16 do
        local data = turtle.getItemDetail(i)
        if data then
            if data.name == item then
                turtle.select(i)
                return true
            end
        end
    end
    return false
end

function dropItems()
    for i = 1, 16 do
        local data = turtle.getItemDetail(i)
        if data then
            if storeItems[data.name] then
                turtle.select(i)
                turtle.dropDown()
            end
        end
    end
end

function move()
    if turtle.getFuelLevel() <= 10 then
        if not selectItem("minecraft:coal") then
            return false
        else
            turtle.refuel(1)
        end
    end
    return turtle.forward()
end

function moveUp()
    if turtle.getFuelLevel() <= 10 then
        if not selectItem("minecraft:coal") then
            return false
        else
            turtle.refuel(1)
        end
    end
    return turtle.up()
end

function moveDown()
    if turtle.getFuelLevel() <= 10 then
        if not selectItem("minecraft:coal") then
            return false
        else
            turtle.refuel(1)
        end
    end
    return turtle.down()
end

function turnAround()
    turtle.turnLeft()
    turtle.turnLeft()
end

function goAround()
    turtle.turnRight()
    move()
    turtle.turnLeft()
    move()
    move()
    turtle.turnLeft()
    move()
    turtle.turnRight()
    checkNext()
end

function returnHelper()
    turtle.turnRight()
    if turtle.inspect() and
        (select(2, turtle.inspect()).name == treeSapling or select(2, turtle.inspect()).name == logType) then
        turtle.turnLeft()
        move()
        move()
        move()
        move()
        returnHelper()
    else
        turtle.turnRight()
        move()
        move()
        move()
        turtle.turnLeft()
        move()
        for i = 1, (currentRow - 1) * 4 do
            if not move() then
                print("Can't move while returning to chest")
                return false
            end
        end
        turtle.turnLeft()
        move()
        if move() then
            dropItems()
            turnAround()
            currentRow = 1
            sleep(180)
            checkNext()
        end
    end
end

function changeRow()
    turnAround()
    local success, data = turtle.inspect()
    while not turtle.inspect() and
        (select(2, turtle.inspect()).name ~= treeSapling or select(2, turtle.inspect()).name ~= logType) do
        if not move() then
            print("Can't move while changing row!")
            return false
        end
    end
    if currentRow == rows then
        if currentRow % 2 == 1 then
            turtle.turnLeft()
            move()
            turtle.turnRight()
            move()
            returnHelper()
        elseif currentRow % 2 == 0 then
            turtle.turnLeft()
            for i = 1, (currentRow - 1) * 4 do
                if not move() then
                    print("Can't move while returning to chest")
                    return false
                end
            end
            turtle.turnLeft()
            move()
            if move() then
                dropItems()
                turnAround()
                currentRow = 1
                sleep(180)
                checkNext()
            end
        end
    elseif currentRow % 2 == 1 then
        turtle.turnLeft()
        for i = 1, 4 do
            if not move() then
                print("Can't move while changing row!")
                return false
            end
        end
        turtle.turnRight()
        currentRow = currentRow + 1
        checkNext()
    elseif currentRow % 2 == 0 then
        turtle.turnRight()
        for i = 1, 4 do
            if not move() then
                print("Can't move while changing row!")
                return false
            end
        end
        turtle.turnLeft()
        currentRow = currentRow + 1
        checkNext()
    end
end

function placeSapling()
    if selectItem(treeSapling) then
        return turtle.place()
    else
        return false
    end
end

function collectSapling()
    for i = 1, 4 do
        turtle.turnLeft()
        turtle.suck()
    end
end

function fallTree()
    local success, data = turtle.inspectUp()
    if success and data.name == logType then
        turtle.digUp()
        moveUp()
        fallTree()
    else
        while not turtle.inspectDown() do
            moveDown()
        end
        collectSapling()
        if move() then
            collectSapling()
            turnAround()
            if placeSapling() then
                turnAround()
                checkNext()
            else
                print("Need more saplings!")
                return
            end
        else
            print("Out of fuel")
            return flase
        end
    end
end

function checkNext()
    move()
    collectSapling()
    move()
    collectSapling()
    local success, data = turtle.inspect()
    if success then
        if data.name == treeSapling then
            goAround()
        elseif data.name == logType then
            turtle.dig()
            move()
            fallTree()
        else
            print("Error while checking next tree")
            return false
        end
    else
        changeRow()
    end
end

checkNext()