Server Up-Time Timer (ComputerCraft)

-- Needs a monitor four blocks wide.

-- Text counts down in white until the next predicted Minecraft server reboot.

-- If the server stays up longer than predicted, text turns grey and starts counting
-- upwards to indicate current uptime instead.

-- Prediction is based upon the longest uptime encountered.

local mon = peripheral.find("monitor")

local counter, maxCount = 0, 0

if fs.exists("lastTime") then
    local input = io.open("lastTime", "r")
    maxCount = tonumber(input:read())
    input:close()
end

print("Last uptime " .. (maxCount / 60) .. " minutes (" .. (maxCount / 3600) .. " hours).")

mon.setTextColour(colours.white)
mon.setBackgroundColour(colours.black)
mon.setTextScale(5)

while true do
    if counter == maxCount then mon.setTextColour(colours.grey) end

    local thisTime

    if counter > maxCount then
        if counter % 60 == 0 then
            local output = io.open("lastTime", "w")
            output:write(counter)
            output:close()
        end

        thisTime = counter
    else
        thisTime = maxCount - counter
    end

    local hours = tostring(math.floor(thisTime / 3600))
    if #hours == 1 then hours = "0" .. hours end

    thisTime = thisTime % 3600

    local minutes = tostring(math.floor(thisTime / 60))
    if #minutes == 1 then minutes = "0" .. minutes end

    local seconds = tostring(thisTime % 60)
    if #seconds == 1 then seconds = "0" .. seconds end

    mon.setCursorPos(1, 1)
    mon.write(hours .. ":" .. minutes .. ":" .. seconds)

    sleep(1)
    counter = counter + 1
end