startup.lua

--different possible groupings and their
--corresponding greetings
local groupings = {
    {"kaibochan"},
    {"kaibochan", "sethrl"},
    {"sethrl"},
    {"N0LIF3RRE3"},
    {"kaibochan", "N0LIF3RRE3"},
    {"N0LIF3RRE3", "sethrl"},
    {"kaibochan", "N0LIF3RRE3", "sethrl"},
}

local greetings = {
    "Welcome back, Kai",
    "Welcome, disciples",
    "Hey cutie ;-)",
    "ICEJJPICK!?",
    "ADHD squad B-)",
    "TWO CUTIES!?\nAT MY BASE!?",
    "What's up CS squad",
}

local settings = {
    {
        ["scale"] = 1,
        ["textColor"] = colors.lime,
        ["bgColor"] = colors.black,
    },
    {
        ["scale"] = 1,
        ["textColor"] = colors.yellow,
        ["bgColor"] = colors.black,
    },
    {
        ["scale"] = 2,
        ["textColor"] = colors.pink,
        ["bgColor"] = colors.black,
    },
    {
        ["scale"] = 2,
        ["textColor"] = colors.black,
        ["bgColor"] = colors.white,
    },
    {
        ["scale"] = 2,
        ["textColor"] = colors.red,
        ["bgColor"] = colors.black,
    },
    {
        ["scale"] = 1,
        ["textColor"] = colors.red,
        ["bgColor"] = colors.white,
    },
    {
        ["scale"] = 1,
        ["textColor"] = colors.lightBlue,
        ["bgColor"] = colors.black,
    },
}

--default text displayed when no players
local defaultText = "Biopunk"

local defaultSettings = {
    ["scale"] = 2,
    ["textColor"] = colors.lime,
    ["bgColor"] = colors.black,
}

function main()
    --find peripherals
    monitor = peripheral.find("monitor")
    playerDetector = peripheral.find("playerDetector")

    --sort each grouping for easy comparison
    for i, group in ipairs(groupings) do
        table.sort(group)
    end

    while true do
        --only activate once every 1/8 of a second
        sleep(1/8)

        monitor.clear()
        monitor.setCursorPos(1, 1)

        --get a sorted list of nearby players
        local players = playerDetector.getPlayersInCubic(2, 2, 2)
        table.sort(players)

        --if no players nearby, display default
        --text
        if #players == 0 then
            monitor.setTextScale(defaultSettings.scale)
            monitor.setTextColor(defaultSettings.textColor)
            monitor.setBackgroundColor(defaultSettings.bgColor)
            monitor.write(defaultText)
        else
            local foundGroup

            --iterate through all different groups
            for i, group in ipairs(groupings) do
                foundGroup = true

                --iterate through names within the
                --current group, checking for a
                --match, then printing the
                --corresponding greeting
                if #players ==  #group then
                    for j, name in ipairs(group) do
                        if players[j] ~= name then
                            foundGroup = false
                        end
                    end
                else
                    foundGroup = false
                end

                if foundGroup then
                    monitor.setTextScale(settings[i].scale)
                    monitor.setTextColor(settings[i].textColor)
                    monitor.setBackgroundColor(settings[i].bgColor)
                    monitor.write(greetings[i])
                    break
                end
            end
        end
    end
end

main()