Elevator

-- Local Variables
local sItem = 1
local cFloor = 1
local inFloorMenu = true
local w, h = term.getSize()



-- Text Functions
function printCentered( text ) -- Centers text on terminal screen
    term.clear()
    term.setCursorPos(w/2-#text/2, h/2)
    print (text)
    sleep(1)
end

-- Handler Functions
function s1() -- Sends rednet message to the control computer
    rednet.open("back") -- Opens the wireless modem
    rednet.send(2, "1", true) -- Sends the message
    rednet.close("back") -- Closes the modem
    cFloor = 1 -- Rewrites the current floor variable for later use
end

function s2() -- Same as above
    rednet.open("back")
    rednet.send(2, "2", true)
    rednet.close("back")
    cFloor = 2
end

function s3() -- Same as above
    rednet.open("back")
    rednet.send(2, "3", true)
    rednet.close("back")
    cFloor = 3
end
--[[ Menu Table
Table containing menu text and the the corresponding functions
]]--
floorMenu = {
[1] = { text = "1st Floor", handler = s1 },
[2] = { text = "2nd Floor", handler = s2 },
[3] = { text = "3rd Floor", handler = s3 }
}

-- Draw Menu

function printMenu( menu ) -- Displays the menu with >> << markers to select floors with.
    for i=1,#menu do
        term.setCursorPos(w/2-#menu[i].text/2-2, h/2-1+i) -- centers the menu
        if i == sItem then
            print (">> "..menu[i].text.." <<") -- Displays markers around the selected floor
        else
            print ("   "..menu[i].text) -- Displays the other floors
        end
    end
end
-- Handler

function onKey( key, menu ) -- Finds out which key was pressed
    if key == keys.enter then -- starts the onItem function
        onItem(menu)
    elseif key == keys.up then -- Moves up in the menu, ie. from floor 3 to 2
        if sItem > 1 then -- Unless it's already at the top
            sItem = sItem - 1
        end
    elseif key == keys.down then -- Moves down in the menu
        if sItem < #menu then -- Unless it's already on the last item in the menu
            sItem = sItem + 1
        end
    end
end

function onItem( menu ) -- starts the menu function(s1, s2 and s3 dependent on which was selected)
    menu[sItem].handler()
end

-- Run Program

function runProgram() -- Main function which starts the program
    while inFloorMenu do -- Runs a loop as long as the inFloorMenu variable is true
        term.clear()
        term.setCursorPos(1,1)
        printMenu(floorMenu) -- calls the print menu function for the floor menu specifically.

        event, key = os.pullEvent("key") -- Checks whether a key has been pressed
        onKey(key,floorMenu) -- Runs the onKey function for the floor menu.
    end
end

runProgram()