16-step colour sequencer

SIDE_INPUT = "left"
SIDE_OUTPUT = "right"
COLOUR_OFFSET = 1
COLOUR_MAX = 16
--DELAY_TIME = 1
CURRENT_COLOUR = 0

function save_config()
    local fHandle = fs.open("config.txt", "w")
    fHandle.writeLine(SIDE_INPUT)
    fHandle.writeLine(SIDE_OUTPUT)
    fHandle.writeLine(COLOUR_OFFSET)
    fHandle.writeLine(COLOUR_MAX)
    --fHandle.writeLine(DELAY_TIME)
    fHandle.close()
end

function load_config()
    local fHandle = fs.open("config.txt", "r")
    SIDE_INPUT = fHandle.readLine()
    SIDE_OUTPUT = fHandle.readLine()
    COLOUR_OFFSET = tonumber(fHandle.readLine())
    COLOUR_MAX = tonumber(fHandle.readLine())
    --DELAY_TIME = tonumber(fHandle.readLine())
    fHandle.close()
end

function verify_side(side)
    if (side == "left") then
        return true
    elseif (side == "right") then
        return true
    elseif (side == "front") then
        return true
    elseif (side == "back") then
        return true
    elseif (side == "top") then
        return true
    elseif (side == "bottom") then
        return true
    else
        return false
    end
end

function numberToColour(num)
    if (num == 1) then
        return colours.white
    elseif (num == 2) then
        return colours.orange
    elseif (num == 3) then
        return colours.magenta
    elseif (num == 4) then
        return colours.lightBlue
    elseif (num == 5) then
        return colours.yellow
    elseif (num == 6) then
        return colours.lime
    elseif (num == 7) then
        return colours.pink
    elseif (num == 8) then
        return colours.grey
    elseif (num == 9) then
        return colours.lightGrey
    elseif (num == 10) then
        return colours.cyan
    elseif (num == 11) then
        return colours.purple
    elseif (num == 12) then
        return colours.blue
    elseif (num == 13) then
        return colours.brown
    elseif (num == 14) then
        return colours.green
    elseif (num == 15) then
        return colours.red
    else
        return colours.black
    end
end

term.setCursorPos(1,1)
term.clear()
if (fs.exists("config.txt")) then
    load_config()
    print("Loaded config!")
else
    print("Enter the input side: ")
    SIDE_INPUT = read();
    if (verify_side(SIDE_INPUT) == false) then
        print("Unknown side: " .. SIDE_INPUT)
        return
    end

    print("Enter the output rednet side: ")
    SIDE_OUTPUT = read()
    if (verify_side(SIDE_OUTPUT) == false) then
        print("Unknown side: " .. SIDE_OUTPUT)
        return
    end

    print("Enter the starting colour number (1-16)")
    COLOUR_OFFSET = tonumber(read());
    if (COLOUR_OFFSET < 1 or COLOUR_OFFSET > 16) then
        print("Colour number (" .. COLOUR_OFFSET .. ") was not between 1 and 16")
        return
    end

    print("Enter the end colour number (" .. COLOUR_OFFSET .. "-16)")
    COLOUR_MAX = tonumber(read());
    if (COLOUR_MAX < 1 or COLOUR_MAX > 16) then
        print("Colour number (" .. COLOUR_MAX .. ") was not between 1 and 16")
        return
    end

    if (COLOUR_OFFSET == COLOUR_MAX) then
        print("Colour offset and max value are the same??? (" .. COLOUR_OFFSET .. ")")
        return
    end

    CURRENT_COLOUR = COLOUR_OFFSET

    --print("Enter the delay time between steps (in seconds)")
    --DELAY_TIME = tonumber(read());
    --if (DELAY_TIME < 0) then
    --    print("Delay cannot be negative!!!")
    --    return
    --end

    save_config()
    print("Saved configuration to file!")
end

while (true) do
    local event = os.pullEvent("redstone")
    if (rs.getInput(SIDE_INPUT)) then
        local col = numberToColour(CURRENT_COLOUR)
        --print("Colour type = " .. type(col) .. ", out type = " .. type(SIDE_OUTPUT))
        -- print("Set colour number: " .. CURRENT_COLOUR .. " (" .. col .. ")")
        redstone.setBundledOutput(SIDE_OUTPUT, col)

        CURRENT_COLOUR = CURRENT_COLOUR + 1
        if (CURRENT_COLOUR > COLOUR_MAX) then
            CURRENT_COLOUR = COLOUR_OFFSET
        end
    end
end