techircd/server.go

package main

import (
	"crypto/tls"
	"fmt"
	"log"
	"net"
	"strings"
	"sync"
	"time"
	"unicode/utf8"
)

type Server struct {
	config         *Config
	clients        map[string]*Client
	channels       map[string]*Channel
	listener       net.Listener
	sslListener    net.Listener
	serverListener net.Listener
	linkedServers  map[string]*LinkedServer
	pingMessage    string
	mu             sync.RWMutex
	shutdown       chan bool
	healthMonitor  *HealthMonitor
	healthCheckSem chan struct{} // Semaphore to limit concurrent health checks
}

func NewServer(config *Config) *Server {
	server := &Server{
		config:         config,
		clients:        make(map[string]*Client, config.Limits.MaxClients),
		channels:       make(map[string]*Channel, config.Limits.MaxChannels),
		shutdown:       make(chan bool),
		healthCheckSem: make(chan struct{}, 1), // Only allow 1 concurrent health check
	}
	server.healthMonitor = NewHealthMonitor(server)
	return server
}

func (s *Server) Start() error {
	// Start regular listener
	addr := fmt.Sprintf("%s:%d", s.config.Server.Listen.Host, s.config.Server.Listen.Port)
	listener, err := net.Listen("tcp", addr)
	if err != nil {
		return fmt.Errorf("failed to listen on %s: %v", addr, err)
	}
	s.listener = listener

	log.Printf("IRC server listening on %s", addr)

	// Start health monitoring
	s.healthMonitor.Start()

	// Start SSL listener if enabled
	if s.config.Server.Listen.EnableSSL {
		go s.startSSLListener()
	}

	// Start server linking if enabled
	if s.config.Linking.Enable {
		go s.startServerListener()
		go s.startAutoConnections()
	}

	// Auto-create configured channels
	for _, channelName := range s.config.Channels.AutoJoin {
		channel := NewChannel(channelName)
		// Set default modes
		for _, mode := range s.config.Channels.DefaultModes {
			if mode != '+' {
				channel.SetMode(rune(mode), true)
			}
		}
		s.channels[strings.ToLower(channelName)] = channel
	}

	// Start ping routine
	go s.pingRoutine()

	// Accept connections
	for {
		select {
		case <-s.shutdown:
			return nil
		default:
			conn, err := listener.Accept()
			if err != nil {
				continue
			}

			client := NewClient(conn, s)
			s.AddClient(client)
			go client.Handle()
		}
	}
}

func (s *Server) startSSLListener() {
	// Validate SSL configuration
	if s.config.Server.SSL.CertFile == "" || s.config.Server.SSL.KeyFile == "" {
		log.Printf("SSL enabled but certificate or key file not specified")
		return
	}

	// Load SSL certificates
	cert, err := tls.LoadX509KeyPair(s.config.Server.SSL.CertFile, s.config.Server.SSL.KeyFile)
	if err != nil {
		log.Printf("CRITICAL: Failed to load SSL certificates (SSL disabled): %v", err)
		log.Printf("SSL will not be available. Check certificate paths in config.")
		return
	}

	tlsConfig := &tls.Config{Certificates: []tls.Certificate{cert}}

	addr := fmt.Sprintf("%s:%d", s.config.Server.Listen.Host, s.config.Server.Listen.SSLPort)
	listener, err := tls.Listen("tcp", addr, tlsConfig)
	if err != nil {
		log.Printf("CRITICAL: Failed to start SSL listener on %s: %v", addr, err)
		log.Printf("SSL will not be available. Server continues with plain connections only.")
		return
	}
	s.sslListener = listener

	log.Printf("✓ IRC SSL server listening on %s", addr)

	for {
		select {
		case <-s.shutdown:
			return
		default:
			conn, err := listener.Accept()
			if err != nil {
				continue
			}

			client := NewClient(conn, s)
			s.AddClient(client)
			go client.Handle()
		}
	}
}

func (s *Server) pingRoutine() {
	ticker := time.NewTicker(60 * time.Second) // Reduced frequency to prevent contention
	defer ticker.Stop()

	// Add a health check ticker that runs less frequently
	healthTicker := time.NewTicker(5 * time.Minute) // Much less frequent health checks
	defer healthTicker.Stop()

	for {
		select {
		case <-s.shutdown:
			return
		case <-ticker.C:
			// Run ping check with semaphore to prevent goroutine leaks
			select {
			case s.healthCheckSem <- struct{}{}:
				go func() {
					defer func() { <-s.healthCheckSem }()
					s.performPingCheck()
				}()
			default:
				// Skip ping check if one is already running
				log.Printf("Skipping ping check - one already in progress")
			}
		case <-healthTicker.C:
			// Run health check with semaphore to prevent goroutine leaks
			select {
			case s.healthCheckSem <- struct{}{}:
				go func() {
					defer func() { <-s.healthCheckSem }()
					s.performHealthCheck()
				}()
			default:
				// Skip health check if one is already running
				log.Printf("Skipping health check - one already in progress")
			}
		}
	}
}

// performPingCheck handles the periodic ping checking
func (s *Server) performPingCheck() {
	defer func() {
		if r := recover(); r != nil {
			log.Printf("Panic in performPingCheck: %v", r)
		}
	}()

	// Get a snapshot of clients without holding the lock for long
	s.mu.RLock()
	clientIDs := make([]string, 0, len(s.clients))
	for clientID := range s.clients {
		clientIDs = append(clientIDs, clientID)
	}
	s.mu.RUnlock()

	// Process clients individually to prevent blocking
	for _, clientID := range clientIDs {
		func() {
			// Get client safely
			s.mu.RLock()
			client := s.clients[clientID]
			s.mu.RUnlock()

			if client == nil || !client.IsRegistered() || !client.IsConnected() {
				return
			}

			// Check activity without holding client lock for long
			client.mu.RLock()
			lastActivity := client.lastActivity
			client.mu.RUnlock()

			// Only send ping if client hasn't been active recently
			if time.Since(lastActivity) > 120*time.Second {
				// Send ping in a non-blocking way
				go func() {
					defer func() {
						if r := recover(); r != nil {
							log.Printf("Panic sending ping to %s: %v", client.getClientInfo(), r)
						}
					}()
					client.SendMessage(s.pingMessage) // Use pre-computed message
				}()
			}
		}()
	}
}

// performHealthCheck checks all clients for health issues
func (s *Server) performHealthCheck() {
	defer func() {
		if r := recover(); r != nil {
			log.Printf("Panic in performHealthCheck: %v", r)
		}
	}()

	// Get a snapshot of clients without holding the lock for long
	s.mu.RLock()
	clientIDs := make([]string, 0, len(s.clients))
	for clientID := range s.clients {
		clientIDs = append(clientIDs, clientID)
	}
	totalClients := len(s.clients)
	s.mu.RUnlock()

	unhealthyClients := 0
	disconnectedClients := []string{} // Store client IDs instead of pointers

	// Process clients in batches to prevent overwhelming the system
	batchSize := 50
	for i := 0; i < len(clientIDs); i += batchSize {
		end := i + batchSize
		if end > len(clientIDs) {
			end = len(clientIDs)
		}

		batch := clientIDs[i:end]
		for _, clientID := range batch {
			func() {
				// Get client safely
				s.mu.RLock()
				client := s.clients[clientID]
				s.mu.RUnlock()

				if client == nil {
					return
				}

				healthy, reason := client.HealthCheck()
				if !healthy {
					unhealthyClients++
					
					// Force disconnect clients that are definitely problematic
					if strings.Contains(reason, "disconnected") ||
						strings.Contains(reason, "nil") ||
						strings.Contains(reason, "write errors") ||
						strings.Contains(reason, "registration timeout") {
						disconnectedClients = append(disconnectedClients, clientID)
						log.Printf("Marking client %s for disconnection: %s", client.getClientInfo(), reason)
					}
				}
			}()
		}

		// Small delay between batches to prevent overwhelming
		time.Sleep(10 * time.Millisecond)
	}

	// Disconnect problematic clients in a separate goroutine
	if len(disconnectedClients) > 0 {
		go func() {
			defer func() {
				if r := recover(); r != nil {
					log.Printf("Panic during client disconnection: %v", r)
				}
			}()

			for _, clientID := range disconnectedClients {
				s.mu.RLock()
				client := s.clients[clientID]
				s.mu.RUnlock()

				if client != nil {
					client.ForceDisconnect("Connection health check failed")
				}
			}
		}()
	}

	// Log health statistics
	if totalClients > 0 {
		healthyPercentage := float64(totalClients-unhealthyClients) / float64(totalClients) * 100
		log.Printf("Client health check: %d total, %d healthy (%.1f%%), %d marked for disconnection",
			totalClients, totalClients-unhealthyClients, healthyPercentage, len(disconnectedClients))
	}

	// Log detailed server statistics every 5 minutes for monitoring
	s.LogServerStats()
}

func (s *Server) AddClient(client *Client) {
	s.mu.Lock()
	defer s.mu.Unlock()

	// Enhanced validation before adding client
	if client == nil {
		log.Printf("Attempted to add nil client")
		return
	}

	if client.conn == nil {
		log.Printf("Attempted to add client with nil connection")
		return
	}

	// Check client limit
	if len(s.clients) >= s.config.Limits.MaxClients {
		log.Printf("Server full, rejecting client from %s", client.getClientInfo())
		client.SendMessage("ERROR :Server full")
		if client.conn != nil {
			client.conn.Close()
		}
		return
	}

	// Check for duplicate client IDs (shouldn't happen but defensive programming)
	if _, exists := s.clients[client.clientID]; exists {
		log.Printf("Duplicate client ID detected: %s, generating new ID", client.clientID)
		// Generate a new unique ID
		client.clientID = fmt.Sprintf("%s_%d_%d", client.host, time.Now().Unix(), len(s.clients))
	}

	s.clients[client.clientID] = client
	log.Printf("Added client %s (total clients: %d/%d)", client.getClientInfo(), len(s.clients), s.config.Limits.MaxClients)
}

func (s *Server) RemoveClient(client *Client) {
	s.mu.Lock()
	delete(s.clients, client.clientID)
	s.mu.Unlock()

	// Send snomask notification for client disconnect (after releasing the lock)
	if client.IsRegistered() {
		s.sendSnomask('c', fmt.Sprintf("Client disconnect: %s (%s@%s)",
			client.Nick(), client.User(), client.Host()))
	}
}

// GetServerStats returns detailed server statistics for monitoring
func (s *Server) GetServerStats() map[string]interface{} {
	s.mu.RLock()
	defer s.mu.RUnlock()

	stats := make(map[string]interface{})

	// Basic counts
	stats["total_clients"] = len(s.clients)
	stats["total_channels"] = len(s.channels)

	// Client statistics
	registeredClients := 0
	operatorClients := 0
	sslClients := 0
	unhealthyClients := 0

	for _, client := range s.clients {
		if client.IsRegistered() {
			registeredClients++
		}
		if client.IsOper() {
			operatorClients++
		}
		if client.IsSSL() {
			sslClients++
		}

		// Quick health check
		if healthy, _ := client.HealthCheck(); !healthy {
			unhealthyClients++
		}
	}

	stats["registered_clients"] = registeredClients
	stats["operator_clients"] = operatorClients
	stats["ssl_clients"] = sslClients
	stats["unhealthy_clients"] = unhealthyClients

	// Channel statistics
	totalChannelUsers := 0
	for _, channel := range s.channels {
		totalChannelUsers += len(channel.GetClients())
	}
	stats["total_channel_users"] = totalChannelUsers

	// Server linking statistics
	stats["linked_servers"] = len(s.linkedServers)

	return stats
}

// LogServerStats logs current server statistics
func (s *Server) LogServerStats() {
	stats := s.GetServerStats()
	log.Printf("Server Statistics: %d clients (%d registered, %d operators, %d SSL, %d unhealthy), %d channels, %d linked servers",
		stats["total_clients"], stats["registered_clients"], stats["operator_clients"],
		stats["ssl_clients"], stats["unhealthy_clients"], stats["total_channels"], stats["linked_servers"])
}

// sendSnomask sends a server notice to operators watching a specific snomask
func (s *Server) sendSnomask(snomask rune, message string) {
	s.mu.RLock()
	defer s.mu.RUnlock()

	for _, client := range s.clients {
		if client.IsOper() && client.HasSnomask(snomask) {
			client.SendMessage(fmt.Sprintf(":%s NOTICE %s :*** %s",
				s.config.Server.Name, client.Nick(), message))
		}
	}
}

// ReloadConfig reloads the server configuration
func (s *Server) ReloadConfig() error {
	config, err := LoadConfig("config.json")
	if err != nil {
		return fmt.Errorf("failed to load config: %v", err)
	}

	s.mu.Lock()
	s.config = config
	s.mu.Unlock()

	return nil
}

func (s *Server) GetClient(nick string) *Client {
	s.mu.RLock()
	defer s.mu.RUnlock()

	for _, client := range s.clients {
		if strings.EqualFold(client.Nick(), nick) {
			return client
		}
	}
	return nil
}

func (s *Server) GetClientByHost(host string) *Client {
	s.mu.RLock()
	defer s.mu.RUnlock()

	for _, client := range s.clients {
		if client.Host() == host {
			return client
		}
	}
	return nil
}

func (s *Server) GetClientByID(clientID string) *Client {
	s.mu.RLock()
	defer s.mu.RUnlock()
	return s.clients[clientID]
}

func (s *Server) GetClients() map[string]*Client {
	s.mu.RLock()
	defer s.mu.RUnlock()

	clients := make(map[string]*Client)
	for clientID, client := range s.clients {
		clients[clientID] = client
	}
	return clients
}

func (s *Server) GetChannel(name string) *Channel {
	s.mu.RLock()
	defer s.mu.RUnlock()
	return s.channels[strings.ToLower(name)]
}

func (s *Server) GetOrCreateChannel(name string) *Channel {
	s.mu.Lock()
	defer s.mu.Unlock()

	channelName := strings.ToLower(name)
	if channel, exists := s.channels[channelName]; exists {
		return channel
	}

	// Create new channel
	channel := NewChannel(name)
	// Set default modes
	for _, mode := range s.config.Channels.DefaultModes {
		if mode != '+' {
			channel.SetMode(rune(mode), true)
		}
	}
	s.channels[channelName] = channel
	return channel
}

func (s *Server) RemoveChannel(name string) {
	s.mu.Lock()
	defer s.mu.Unlock()
	delete(s.channels, strings.ToLower(name))
}

func (s *Server) GetChannels() map[string]*Channel {
	s.mu.RLock()
	defer s.mu.RUnlock()

	channels := make(map[string]*Channel)
	for name, channel := range s.channels {
		channels[name] = channel
	}
	return channels
}

func (s *Server) CreateChannel(name string) *Channel {
	s.mu.Lock()
	defer s.mu.Unlock()

	if len(s.channels) >= s.config.Limits.MaxChannels {
		return nil
	}

	channel := NewChannel(name)
	s.channels[strings.ToLower(name)] = channel
	return channel
}

func (s *Server) GetClientCount() int {
	s.mu.RLock()
	defer s.mu.RUnlock()
	return len(s.clients)
}

func (s *Server) GetChannelCount() int {
	s.mu.RLock()
	defer s.mu.RUnlock()
	return len(s.channels)
}

func (s *Server) IsNickInUse(nick string) bool {
	s.mu.RLock()
	defer s.mu.RUnlock()

	for _, client := range s.clients {
		if strings.EqualFold(client.Nick(), nick) {
			return true
		}
	}
	return false
}

func (s *Server) HandleMessage(client *Client, message string) {
	// Input validation
	if len(message) == 0 {
		return
	}

	// Check for maximum message length (IRC RFC limits to 512 bytes)
	if len(message) > 510 { // 510 to account for CRLF
		log.Printf("Message too long from %s (%d bytes), dropping", client.Host(), len(message))
		return
	}

	// Check for null bytes (not allowed in IRC messages)
	if strings.ContainsRune(message, '\x00') {
		log.Printf("Message contains null bytes from %s, dropping", client.Host())
		return
	}

	// Basic UTF-8 validation
	if !utf8.ValidString(message) {
		log.Printf("Message contains invalid UTF-8 from %s, dropping", client.Host())
		return
	}

	// Parse IRCv3 message tags if present
	var tags map[string]string
	var actualMessage string
	
	if strings.HasPrefix(message, "@") {
		// Message has IRCv3 tags
		spaceIndex := strings.Index(message, " ")
		if spaceIndex == -1 {
			// Message is only tags (like typing indicators), this is valid - just ignore
			if DebugMode {
				log.Printf("<<< RECV from %s: %s (tags-only message, ignoring)", client.Host(), message)
			}
			return
		}
		
		tagString := message[1:spaceIndex] // Remove @ prefix
		actualMessage = strings.TrimSpace(message[spaceIndex+1:])
		
		// Parse tags
		tags = make(map[string]string)
		tagPairs := strings.Split(tagString, ";")
		for _, pair := range tagPairs {
			if strings.Contains(pair, "=") {
				kv := strings.SplitN(pair, "=", 2)
				tags[kv[0]] = kv[1]
			} else {
				tags[pair] = ""
			}
		}
		
		// If actualMessage is empty or just a colon, it's a tags-only message
		if actualMessage == "" || actualMessage == ":" {
			if DebugMode {
				log.Printf("<<< RECV from %s: %s (tags-only message, ignoring)", client.Host(), message)
			}
			return
		}
	} else {
		actualMessage = message
	}
	
	parts := strings.Fields(actualMessage)
	if len(parts) == 0 {
		return
	}

	command := strings.ToUpper(parts[0])

	// Log the command for debugging
	if DebugMode {
		log.Printf("<<< RECV from %s: %s", client.Host(), message)
	} else {
		log.Printf("Client %s: %s", client.Host(), message)
	}

	switch command {
	case "CAP":
		client.handleCap(parts)
	case "NICK":
		client.handleNick(parts)
	case "USER":
		client.handleUser(parts)
	case "PING":
		client.handlePing(parts)
	case "PONG":
		client.handlePong(parts)
	case "JOIN":
		client.handleJoin(parts)
	case "PART":
		client.handlePart(parts)
	case "PRIVMSG":
		client.handlePrivmsg(parts)
	case "NOTICE":
		client.handleNotice(parts)
	case "TAGMSG":
		client.handleTagmsg(parts, tags)
	case "WHO":
		client.handleWho(parts)
	case "WHOIS":
		client.handleWhois(parts)
	case "NAMES":
		client.handleNames(parts)
	case "MODE":
		client.handleMode(parts)
	case "OPER":
		client.handleOper(parts)
	case "SNOMASK":
		client.handleSnomask(parts)
	case "GLOBALNOTICE":
		client.handleGlobalNotice(parts)
	case "OPERWALL":
		client.handleOperWall(parts)
	case "WALLOPS":
		client.handleWallops(parts)
	case "REHASH":
		client.handleRehash()
	case "TRACE":
		client.handleTrace(parts)
	case "HELPOP":
		client.handleHelpop(parts)
	case "TOPIC":
		client.handleTopic(parts)
	case "KICK":
		client.handleKick(parts)
	case "INVITE":
		client.handleInvite(parts)
	case "AWAY":
		client.handleAway(parts)
	case "LIST":
		client.handleList()
	case "KILL":
		client.handleKill(parts)
	case "QUIT":
		client.handleQuit(parts)
	case "CONNECT":
		client.handleConnect(parts)
	case "SQUIT":
		client.handleSquit(parts)
	case "LINKS":
		client.handleLinks()
	case "USERHOST":
		client.handleUserhost(parts)
	case "ISON":
		client.handleIson(parts)
	case "TIME":
		client.handleTime()
	case "VERSION":
		client.handleVersion()
	case "ADMIN":
		client.handleAdmin()
	case "INFO":
		client.handleInfo()
	case "LUSERS":
		client.handleLusers()
	case "STATS":
		client.handleStats(parts)
	case "SILENCE":
		client.handleSilence(parts)
	case "MONITOR":
		client.handleMonitor(parts)
	case "AUTHENTICATE":
		client.handleAuthenticate(parts)
	// Services/Admin Commands
	case "CHGHOST":
		client.handleChghost(parts)
	case "SVSNICK":
		client.handleSvsnick(parts)
	case "SVSMODE":
		client.handleSvsmode(parts)
	case "SAMODE":
		client.handleSamode(parts)
	case "SANICK":
		client.handleSanick(parts)
	case "SAKICK":
		client.handleSakick(parts)
	case "SAPART":
		client.handleSapart(parts)
	case "SAJOIN":
		client.handleSajoin(parts)
	case "WHOWAS":
		client.handleWhowas(parts)
	case "MOTD":
		client.handleMotd()
	case "RULES":
		client.handleRules()
	case "MAP":
		client.handleMap()
	case "KNOCK":
		client.handleKnock(parts)
	case "SETNAME":
		client.handleSetname(parts)
	case "DIE":
		client.handleDie()
	default:
		client.SendNumeric(ERR_UNKNOWNCOMMAND, command+" :Unknown command")
	}
}

// Shutdown gracefully shuts down the server
func (s *Server) Shutdown() {
	log.Println("Initiating graceful shutdown...")

	// Stop health monitoring first to prevent interference
	if s.healthMonitor != nil {
		s.healthMonitor.Stop()
	}

	// Close listeners immediately to stop accepting new connections
	go func() {
		if s.listener != nil {
			s.listener.Close()
		}
		if s.sslListener != nil {
			s.sslListener.Close()
		}
		if s.serverListener != nil {
			s.serverListener.Close()
		}
	}()

	// Signal shutdown to all goroutines (non-blocking)
	select {
	case <-s.shutdown:
		// Already closed
	default:
		close(s.shutdown)
	}

	// Disconnect all linked servers in background
	go func() {
		defer func() {
			if r := recover(); r != nil {
				log.Printf("Panic during server disconnection: %v", r)
			}
		}()
		
		s.mu.RLock()
		linkedServers := make([]*LinkedServer, 0, len(s.linkedServers))
		for _, server := range s.linkedServers {
			linkedServers = append(linkedServers, server)
		}
		s.mu.RUnlock()
		
		for _, linkedServer := range linkedServers {
			linkedServer.Disconnect()
		}
	}()

	// Notify and disconnect all clients with timeout
	go func() {
		defer func() {
			if r := recover(); r != nil {
				log.Printf("Panic during client disconnection: %v", r)
			}
		}()
		
		// Get client IDs without holding lock for long
		s.mu.RLock()
		clientIDs := make([]string, 0, len(s.clients))
		for clientID := range s.clients {
			clientIDs = append(clientIDs, clientID)
		}
		s.mu.RUnlock()

		// Disconnect clients in batches to prevent overwhelming
		batchSize := 10
		for i := 0; i < len(clientIDs); i += batchSize {
			end := i + batchSize
			if end > len(clientIDs) {
				end = len(clientIDs)
			}

			batch := clientIDs[i:end]
			for _, clientID := range batch {
				s.mu.RLock()
				client := s.clients[clientID]
				s.mu.RUnlock()

				if client != nil {
					// Send shutdown message with timeout
					go func(c *Client) {
						defer func() {
							if r := recover(); r != nil {
								log.Printf("Panic notifying client during shutdown: %v", r)
							}
						}()
						c.SendMessage("ERROR :Server shutting down")
						// Give client time to process message
						time.Sleep(100 * time.Millisecond)
						c.ForceDisconnect("Server shutdown")
					}(client)
				}
			}
			
			// Small delay between batches
			time.Sleep(50 * time.Millisecond)
		}
	}()

	// Give everything time to shut down gracefully
	time.Sleep(2 * time.Second)

	log.Println("Server shutdown complete")
}

// Server linking methods

// startServerListener starts listening for incoming server connections
func (s *Server) startServerListener() {
	if !s.config.Linking.Enable {
		return
	}

	addr := fmt.Sprintf("%s:%d", s.config.Server.Listen.Host, s.config.Linking.ServerPort)
	listener, err := net.Listen("tcp", addr)
	if err != nil {
		log.Printf("Failed to start server listener on %s: %v", addr, err)
		return
	}

	s.serverListener = listener
	log.Printf("IRC server listening for server links on %s", addr)

	for {
		select {
		case <-s.shutdown:
			return
		default:
			conn, err := listener.Accept()
			if err != nil {
				continue
			}

			log.Printf("Incoming server connection from %s", conn.RemoteAddr())
			go s.handleIncomingServer(conn)
		}
	}
}

// startAutoConnections attempts to connect to configured auto-connect servers
func (s *Server) startAutoConnections() {
	if !s.config.Linking.Enable {
		return
	}

	// Wait a bit before starting auto-connections
	time.Sleep(5 * time.Second)

	for _, link := range s.config.Linking.Links {
		if link.AutoConnect {
			go s.connectToServer(link.Name, link.Host, link.Port, link.Password, link.Hub, link.Description)
		}
	}
}

// connectToServer connects to a remote server
func (s *Server) connectToServer(name, host string, port int, password string, hub bool, description string) {
	linkedServer := NewLinkedServer(name, host, port, password, hub, description, s)

	s.mu.Lock()
	s.linkedServers[name] = linkedServer
	s.mu.Unlock()

	for {
		select {
		case <-s.shutdown:
			return
		default:
			if !linkedServer.IsConnected() {
				log.Printf("Attempting to connect to server %s at %s:%d", name, host, port)
				if err := linkedServer.Connect(); err != nil {
					log.Printf("Failed to connect to server %s: %v", name, err)
					time.Sleep(30 * time.Second) // Wait before retry
					continue
				}
				log.Printf("Successfully connected to server %s", name)
			}

			// Sleep before checking again
			time.Sleep(60 * time.Second)
		}
	}
}

// handleIncomingServer handles an incoming server connection
func (s *Server) handleIncomingServer(conn net.Conn) {
	defer conn.Close()

	log.Printf("Handling incoming server connection from %s", conn.RemoteAddr())

	// Create a temporary linked server for authentication
	tempServer := &LinkedServer{
		conn:      conn,
		server:    s,
		connected: true,
	}

	// Handle the connection (this will process authentication)
	tempServer.Handle()
}

// AddLinkedServer adds a linked server to the server
func (s *Server) AddLinkedServer(linkedServer *LinkedServer) {
	s.mu.Lock()
	defer s.mu.Unlock()
	s.linkedServers[linkedServer.Name()] = linkedServer
}

// RemoveLinkedServer removes a linked server
func (s *Server) RemoveLinkedServer(name string) {
	s.mu.Lock()
	defer s.mu.Unlock()
	if linkedServer, exists := s.linkedServers[name]; exists {
		linkedServer.Disconnect()
		delete(s.linkedServers, name)
	}
}

// GetLinkedServer returns a linked server by name
func (s *Server) GetLinkedServer(name string) *LinkedServer {
	s.mu.RLock()
	defer s.mu.RUnlock()
	return s.linkedServers[name]
}

// GetLinkedServers returns all linked servers
func (s *Server) GetLinkedServers() map[string]*LinkedServer {
	s.mu.RLock()
	defer s.mu.RUnlock()

	servers := make(map[string]*LinkedServer)
	for name, server := range s.linkedServers {
		servers[name] = server
	}
	return servers
}

// BroadcastToServers sends a message to all linked servers
func (s *Server) BroadcastToServers(message string) {
	s.mu.RLock()
	defer s.mu.RUnlock()

	for _, linkedServer := range s.linkedServers {
		if linkedServer.IsConnected() {
			linkedServer.SendMessage(message)
		}
	}
}

// Ban management functions

// parseDuration parses duration strings like "1d", "2h", "30m", "0" (permanent)
func parseDuration(durationStr string) time.Duration {
	if durationStr == "0" {
		return 0 // Permanent
	}
	
	if len(durationStr) < 2 {
		return 24 * time.Hour // Default to 1 day
	}
	
	unit := durationStr[len(durationStr)-1]
	valueStr := durationStr[:len(durationStr)-1]
	
	var value int
	fmt.Sscanf(valueStr, "%d", &value)
	
	switch unit {
	case 's':
		return time.Duration(value) * time.Second
	case 'm':
		return time.Duration(value) * time.Minute
	case 'h':
		return time.Duration(value) * time.Hour
	case 'd':
		return time.Duration(value) * 24 * time.Hour
	case 'w':
		return time.Duration(value) * 7 * 24 * time.Hour
	default:
		return 24 * time.Hour // Default to 1 day
	}
}