Multi-floor Turtle Elevator

local floor = 1
local pulses = 0
local timer

local function goToFloor(n)
    print("Going to floor " .. n)
    turtle.refuel()
    while floor ~= n do
        if n > floor then
            repeat turtle.up() until rs.getInput("back")
            floor = floor + 1
        elseif n < floor then
            repeat turtle.down() until rs.getInput("back")
            floor = floor - 1
        else break end
    end
    redstone.setOutput("left", true)
    local file = fs.open("floor.txt", "w")
    file.writeLine(floor)
    file.close()
    sleep(0.4)
    redstone.setOutput("left", false)
end

redstone.setOutput("right", true)
redstone.setOutput("left", false)

if fs.exists("floor.txt") then
    local file = fs.open("floor.txt", "r")
    floor = tonumber(file.readLine()) or floor
    file.close()
end

while true do
    local ev = {os.pullEvent()}
    if ev[1] == "redstone" and redstone.getInput("front") then
        if timer then os.cancelTimer(timer) end
        timer = os.startTimer(2)
        pulses = pulses + 1
    elseif ev[1] == "timer" and ev[2] == timer then
        timer = nil
        goToFloor(pulses)
        pulses = 0
    end
end