Minecraft Computer Craft Play Time Tracker

-- Run on a computer craft command computer
-- Will track the play time of players as they connect saving each players time to their own file
-- Will also display in chat players total time upon connecting and session time upon disconnecting
-- Uses vanilla command /list to get current online players so no peripherals needed
-- It will expect a monitor to be placed somewhere around the computer to display stats

PlayerData = {}

local function splitStr (inputstr)
    local t={}
    for str in string.gmatch(inputstr, "([^%s]+)") do
        table.insert(t, str)
    end
    return t
end

local function formatSeconds(seconds)
    local days = math.floor(seconds/86400)
    local hours = math.floor(math.mod(seconds, 86400)/3600)
    local minutes = math.floor(math.mod(seconds,3600)/60)
    local seconds = math.floor(math.mod(seconds,60))
    return string.format("%d:%02d:%02d:%02d",days,hours,minutes,seconds)
end

local function getOnlinePlayers()
    local list = {}
    local success, playersStr = commands.exec("list")
    playersStr[1] = string.gsub(playersStr[1], ",", "")
    local playersStrTable = splitStr(playersStr[1])
    local startIndex = false

    for _,p in ipairs(playersStrTable) do
        if startIndex then
            list[p] = p
        end
        if p == "online:" and not startIndex then
            startIndex = true
        end
    end
    return list
end

local function removeOldPlayers()
    local onlinePlayers = getOnlinePlayers()
    for i,pd in pairs(PlayerData) do
        if not onlinePlayers[i] then
            commands.say(i.." disconnected after playing for "..formatSeconds(PlayerData[i]["session"]))
            PlayerData[i] = nil
        end
    end
end
local function loadPlayerData(player)
    if fs.exists(player..".txt") then
        local playerFile = fs.open(player..".txt", "r")
        PlayerData[player] = {};
        PlayerData[player]["total"] = tonumber(playerFile.readLine())
        PlayerData[player]["session"] = 0
        playerFile.close()
    else
        PlayerData[player] = {};
        PlayerData[player]["total"] = 0
        PlayerData[player]["session"] = 0
    end
end

local function updatePlaytime()
    removeOldPlayers()

    for i,p in pairs(getOnlinePlayers()) do
        if not PlayerData[p] then
            loadPlayerData(p)
            commands.say(p.." joined with "..formatSeconds(PlayerData[p]["total"]).." total playtime")
        end
        PlayerData[p]["session"] = PlayerData[p]["session"]+1
        PlayerData[p]["total"] = PlayerData[p]["total"]+1
        local playerFile = fs.open(p..".txt", "w")
        playerFile.write(PlayerData[p]["total"])
        playerFile.close()
    end
end

local cursorY = 1

m = peripheral.find("monitor")
m.setCursorPos(1,cursorY)
m.clear()
m.setBackgroundColor(colors.black)
m.setTextColor(colors.white)
m.setTextScale(1.5)


while true do
    updatePlaytime()
    m.clear()
    cursorY = 1

    m.setCursorPos(1,cursorY)
    cursorY = cursorY+1
    m.write(os.date("%b %d %G %I:%M %p"))

    for i,p in pairs(getOnlinePlayers()) do
        if PlayerData[p] then
            m.setCursorPos(1,cursorY)
            cursorY = cursorY+1
            m.write(p)
            m.setCursorPos(3,cursorY)
            cursorY = cursorY+1
            m.write("Session: "..formatSeconds(PlayerData[p]["session"]))
            m.setCursorPos(3,cursorY)
            cursorY = cursorY+1
            m.write("  Total: "..formatSeconds(PlayerData[p]["total"]))
        end
    end
    sleep(1)
end