sense

STD_MONITOR_SIDE = "top"

PLAYER_WHITELIST = {
    mc1030 = true,
    ime990 = true,
    Ajfree = true,
    shirograhm = true,
    RadicalRagu = true
}

local moni = peripheral.wrap(STD_MONITOR_SIDE)


local sensor = peripheral.wrap("right")
local entities = {}
local entity_size = 0
local new_entities = {}
local new_entity_size = 0


function welcome(name)
    moni.setTextColor(colors.white)
    print("Welcome "..name)
    monitor_write("Welcome "..name)
end

function farewell(name)
    moni.setTextColor(colors.lightBlue)
    print("\tGodspeed "..name)
    monitor_write("\tGodspeed "..name)
end

function monitor_reset()
    moni.clear()
    moni.setCursorPos(1, 1)
    moni.setTextColor(colors.white)
    moni.setTextScale(0.5)
end

function monitor_write(message)
    moni.write(message)
    local x,y = moni.getCursorPos()
    if y > 8 then
        y = 0
    end
    moni.setCursorPos(1, y + 1)
end

monitor_reset()

while true do
    new_entities = {}
    for _, entity in pairs(sensor.sense()) do
        if PLAYER_WHITELIST[entity.name] ~= nil then

            if entity_size == 0 then
                welcome(entity.name)
            elseif entities ~= nil and entities[entity.name] == nil then
                new_entities[entity.name] = true
                welcome(entity.name)
            end
            new_entities[entity.name] = true
            new_entity_size = new_entity_size + 1
        end
    end

    for name, bool in pairs(entities) do
        if PLAYER_WHITELIST[name] ~= nil then
            if new_entities[name] == nil then
                farewell(name)
            end
        end
    end
    entities = new_entities
    entity_size = new_entity_size
    os.sleep(1.5)
end