-- Server-side code to handle user authentication requests

local SERVER_PORT = 5000
local USERS_FOLDER = "/disk/users/"
local DOMAIN_FILE = "/disk/domain.txt"

local function handleClient(client)
    local computerID = client.read()
    local username = client.read()
    local password = client.read()

    -- Check if the computer ID is valid
    local domainFile = fs.open(DOMAIN_FILE, "r")
    local allowedID = domainFile.readLine()
    domainFile.close()

    if computerID ~= allowedID then
        client.write("FAIL")
        client.close()
        return
    end

    -- Check user credentials
    local passwordFile = fs.combine(USERS_FOLDER .. username, "password.txt")
    if fs.exists(passwordFile) then
        local file = fs.open(passwordFile, "r")
        local storedPassword = file.readLine()
        file.close()

        if password == storedPassword then
            client.write("OK")
        else
            client.write("FAIL")
        end
    else
        client.write("FAIL")
    end

    client.close()
end

local function startServer()
    local socket = require("socket")
    local server = socket.tcp()
    server:bind("*", SERVER_PORT)
    server:listen()

    while true do
        local client = server:accept()
        parallel.waitForAny(
            function()
                handleClient(client)
            end
        )
    end
end

startServer()