Tree Chopper

height = 0

function checkFuel()
    if turtle.getFuelLevel() >= 14 then
        return true
    else
        return false
    end
end

function sortInv()
    for x=1, 16 do
        turtle.select(x)
        if turtle.getItemDetail().name == "Spruce Sapling" then
            turtle.transferTo(16)
        end
    end
end

function harvestTree()
    if fuelCheck() == true then
        turtle.moveDown()
        turtle.dig()
        turtle.moveUp()
        sortInv()
        turtle.select(16)
        turtle.place()
        while turtle.detect() do
            turtle.dig()
            if turtle.detectUp() then
                turtle.digUp()
            end
            turlle.moveUp()
            height = height + 1
        end
        for x=1, height do
            turtle.moveDown()
            height = height -1
        end
    end
end

while turtle.detect() do
    harvestTree()
    sleep(1)
end