modem_location = "back"


rednet.host("lns", "default")
rednet.open(modem_location)

local data = {}

function save_data()
    db = fs.open("lns.db", "w")
    db.write(textutils.serialize(data))
    db.close()
end

function load_data()
    if fs.exists("lns.db") then
        db = fs.open("lns.db", "r")
        db_contents = db.readAll()
        db.close()

        data = textutils.unserialize(db_contents)
    end
end

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

load_data()

while true do
    client_id, msg = rednet.receive()

    -- split string msg into action and hostname with ':' as a delimiter using string.unpack
    local action, hostname = split(msg, ":")

    if action == "lookup" then

        -- check if hostname in data
        if data[hostname] == nil then
            rednet.send(client_id, "not found")
        else
            rednet.send(client_id, data[hostname])
        end
    end
    
    if action == "reload" then
        load_data()
        rednet.send(client_id, "ok")
    end

    if action == "register" then
        data[hostname] = client_id
        save_data()
        rednet.send(client_id, "ok")
    end
end