Elevator Control

--[[ Notes ]]--
--[[
    -- It is a good thing to organize your code.
    -- I have placed comments explaining the code.
    -- You should put your functions and variables before the code that calls them, so they aren't  "nil"
    -- The floor number is not known when the computer is restarted, so you should send it to the floor it's not on to set it, or it can go either way.
--]]
--[[ Local Variables ]]--
Listen = true -- Start the loop to listen for key presses
if fs.exists("floor.txt") then -- Is the floor location saved?
    f = fs.open("floor.txt", "r") -- Open "floor.txt" in read mode
    GetN = f.readLine() -- Get the number from the file
    f.close() -- close the file
    n = tonumber(GetN) -- Change "n" to n... Making it a number instead of a string (string in " 's and number not in " 's)
else
    n = nil
end

--[[ Functions ]]--
-- Elevator --
function elevateDown() -- You define the function
  redstone.setOutput("top", true) -- You power redstone on the top of the computer
  sleep(0.5) -- Sleep for 0.5 seconds
  redstone.setOutput("top", false) -- You take out the power for the top of the computer
end -- End the function

function elevateUp()
  redstone.setOutput("bottom", true) -- You power redstone on the top of the computer
  sleep(0.5)
  redstone.setOutput("bottom", false) -- You take out the power from the bottom of the computer
end

while Listen do -- While you want to have someone press keys, do the following code:
    repeat -- Start a repeat loop
        event, key = os.pullEvent('key') -- Listen for a key event
        os.sleep(0.1)
    until key -- Exit loop when key has been pressed
    if key == 200 then -- Check if up key was pressed
        if n == 1 then -- Check if elevator is already at the top floor
            print("Elevator is already at the top floor.") -- Tell the player the elevator is already at the top floor
        else
            n = 1 -- Set the floor value
            Listen = false -- Exit the loop to listen for keys
        end
    elseif key == 208 then -- Check if down key was pressed
        if n == 2 then
            print("Elevator is already at the bottom floor.")
        else
            n = 2
            Listen = false
        end
    else -- If the key pressed was invalid...
        print("Please press Up or Down key.") -- Tell the player, and then reset the loop!
    end
end

while not Listen do -- Starts elevator actions when not listening for key presses.
    if n == 1 then -- Should the elevator go up?
        for i=1,11 do
            elevateUp() -- Run the function "elevateUp()"
            sleep(0.5)
        end
        f = fs.open("floor.txt", "w") -- Open "floor.txt" in "write" mode
        f.writeLine(n) -- Write the value of "n" to the file
        f.close() -- Close the file
        os.reboot()
    elseif n == 2 then -- Should the elevator go down?
        for i = 1, 11 do
            elevateDown() -- Run the function "elevateDown()"
            sleep(0.5)
        end
        f = fs.open("floor.txt", "w")
        f.writeLine(n)
        f.close()
        os.reboot()
    end
end