Computercraft Simple Tree Turtle

local saplings = {"minecraft:oak_sapling", "minecraft:spruce_sapling", "minecraft:birch_sapling", "minecraft:jungle_sapling"}
local logs = {"minecraft:oak_log", "minecraft:spruce_log", "minecraft:brich_log", "minecraft:jungle_log"}
local turningRight = true

function fell()
    success, data = turtle.inspect()
    successDown = turtle.inspectDown()
    breaker = false

    if success then

        -- Log
        while inTable(data.name, logs) do

            -- os.sleep(0.5)
            turtle.dig()
            turtle.digUp()
            turtle.up()
            success, data = turtle.inspect()
            successDown = turtle.inspectDown()

        end

        -- Reset
        while not (success and successDown) do
            turtle.down()
            successDown = turtle.inspectDown()
            if successDown then replant() end
            success, data = turtle.inspect()
        end

    end
end

function replant()
    for i = 1, 16 do
        turtle.select(i)
        iData = turtle.getItemDetail()
        if not (iData == nil) then
            if inTable(iData.name, saplings) then
                turtle.place()
                break
            end
        end
    end
end

function refuel()
    for i = 1, 16 do
        turtle.select(i)
        if turtle.refuel(0) then
            local halfStack = math.ceil(turtle.getItemCount(i)/2)
            turtle.refuel(halfStack)
        end
    end
end

function inTable(obj, table)
    for i in pairs(table) do
        if obj == table[i] then return true end
    end
    return false
end

function shiftRight()
    turtle.turnRight()
    turtle.forward()
    turtle.turnLeft()
end

function shiftLeft()
    turtle.turnLeft()
    turtle.forward()
    turtle.turnRight()
end

function move()
    success, data = turtle.inspect()
    if not (inTable(data.name, saplings) or inTable(data.name, logs)) then
        turningRight = not turningRight
    end
    if turningRight then shiftRight()
    else shiftLeft()
    end
end

while true do
    if turtle.getFuelLevel() < 11 then
        refuel()
    end
    move()
    -- os.sleep(0.5)
    fell()

end