feat: add IRC wire protocol listener with shared service layer

Add a traditional IRC wire protocol listener (RFC 1459/2812) on
configurable port (default :6667), sharing business logic with
the HTTP API via a new service layer.

- IRC listener: NICK, USER, PASS, JOIN, PART, PRIVMSG, NOTICE,
  TOPIC, MODE, KICK, QUIT, NAMES, LIST, WHOIS, WHO, AWAY, OPER,
  INVITE, LUSERS, MOTD, PING/PONG, CAP
- Service layer: shared logic for both transports including
  channel join (with Tier 2 checks: ban/invite/key/limit),
  message send (with ban + moderation checks), nick change,
  topic, kick, mode, quit broadcast, away, oper, invite
- BroadcastQuit uses FanOut pattern (one insert, N enqueues)
- HTTP handlers delegate to service for all command logic
- Tier 2 mode operations (+b/+i/+s/+k/+l) use service methods

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

internal/ircserver/conn.go

@@ -0,0 +1,501 @@
+package ircserver
+
+import (
+	"bufio"
+	"context"
+	"fmt"
+	"log/slog"
+	"net"
+	"strconv"
+	"strings"
+	"sync"
+	"time"
+
+	"git.eeqj.de/sneak/neoirc/internal/broker"
+	"git.eeqj.de/sneak/neoirc/internal/config"
+	"git.eeqj.de/sneak/neoirc/internal/db"
+	"git.eeqj.de/sneak/neoirc/internal/service"
+	"git.eeqj.de/sneak/neoirc/pkg/irc"
+)
+
+const (
+	maxLineLen     = 512
+	readTimeout    = 5 * time.Minute
+	writeTimeout   = 30 * time.Second
+	dnsTimeout     = 3 * time.Second
+	pollInterval   = 100 * time.Millisecond
+	pingInterval   = 90 * time.Second
+	pongDeadline   = 30 * time.Second
+	maxNickLen     = 32
+	minPasswordLen = 8
+)
+
+// cmdHandler is the signature for registered IRC command
+// handlers.
+type cmdHandler func(ctx context.Context, msg *Message)
+
+// Conn represents a single IRC client TCP connection.
+type Conn struct {
+	conn      net.Conn
+	log       *slog.Logger
+	database  *db.Database
+	brk       *broker.Broker
+	cfg       *config.Config
+	svc       *service.Service
+	serverSfx string
+	commands  map[string]cmdHandler
+
+	mu        sync.Mutex
+	nick      string
+	username  string
+	realname  string
+	hostname  string
+	remoteIP  string
+	sessionID int64
+	clientID  int64
+
+	registered bool
+	gotNick    bool
+	gotUser    bool
+	passWord   string
+
+	lastQueueID int64
+	closed      bool
+	cancel      context.CancelFunc
+}
+
+func newConn(
+	ctx context.Context,
+	tcpConn net.Conn,
+	log *slog.Logger,
+	database *db.Database,
+	brk *broker.Broker,
+	cfg *config.Config,
+	svc *service.Service,
+) *Conn {
+	host, _, _ := net.SplitHostPort(tcpConn.RemoteAddr().String())
+
+	srvName := cfg.ServerName
+	if srvName == "" {
+		srvName = "neoirc"
+	}
+
+	conn := &Conn{ //nolint:exhaustruct // zero-value defaults
+		conn:      tcpConn,
+		log:       log,
+		database:  database,
+		brk:       brk,
+		cfg:       cfg,
+		svc:       svc,
+		serverSfx: srvName,
+		remoteIP:  host,
+		hostname:  resolveHost(ctx, host),
+	}
+
+	conn.commands = conn.buildCommandMap()
+
+	return conn
+}
+
+// buildCommandMap returns a map from IRC command strings
+// to handler functions.
+func (c *Conn) buildCommandMap() map[string]cmdHandler {
+	return map[string]cmdHandler{
+		irc.CmdPing: func(_ context.Context, msg *Message) {
+			c.handlePing(msg)
+		},
+		"PONG":         func(context.Context, *Message) {},
+		irc.CmdNick:    c.handleNick,
+		irc.CmdPrivmsg: c.handlePrivmsg,
+		irc.CmdNotice:  c.handlePrivmsg,
+		irc.CmdJoin:    c.handleJoin,
+		irc.CmdPart:    c.handlePart,
+		irc.CmdQuit: func(_ context.Context, msg *Message) {
+			c.handleQuit(msg)
+		},
+		irc.CmdTopic:  c.handleTopic,
+		irc.CmdMode:   c.handleMode,
+		irc.CmdNames:  c.handleNames,
+		irc.CmdList:   func(ctx context.Context, _ *Message) { c.handleList(ctx) },
+		irc.CmdWhois:  c.handleWhois,
+		irc.CmdWho:    c.handleWho,
+		irc.CmdLusers: func(ctx context.Context, _ *Message) { c.handleLusers(ctx) },
+		irc.CmdMotd:   func(context.Context, *Message) { c.deliverMOTD() },
+		irc.CmdOper:   c.handleOper,
+		irc.CmdAway:   c.handleAway,
+		irc.CmdKick:   c.handleKick,
+		irc.CmdPass:   c.handlePassPostReg,
+		"INVITE":      c.handleInvite,
+		"CAP": func(_ context.Context, msg *Message) {
+			c.handleCAP(msg)
+		},
+		"USERHOST": c.handleUserhost,
+	}
+}
+
+// resolveHost does a reverse DNS lookup, returning the IP
+// on failure.
+func resolveHost(ctx context.Context, addr string) string {
+	ctx, cancel := context.WithTimeout(ctx, dnsTimeout)
+	defer cancel()
+
+	resolver := &net.Resolver{} //nolint:exhaustruct
+
+	names, err := resolver.LookupAddr(ctx, addr)
+	if err != nil || len(names) == 0 {
+		return addr
+	}
+
+	return strings.TrimSuffix(names[0], ".")
+}
+
+// serve is the main loop for a single IRC client connection.
+func (c *Conn) serve(ctx context.Context) {
+	ctx, c.cancel = context.WithCancel(ctx)
+	defer c.cleanup(ctx)
+
+	scanner := bufio.NewScanner(c.conn)
+	scanner.Buffer(make([]byte, maxLineLen), maxLineLen)
+
+	for {
+		_ = c.conn.SetReadDeadline(
+			time.Now().Add(readTimeout),
+		)
+
+		if !scanner.Scan() {
+			return
+		}
+
+		line := scanner.Text()
+		if line == "" {
+			continue
+		}
+
+		msg := ParseMessage(line)
+		if msg == nil {
+			continue
+		}
+
+		c.handleMessage(ctx, msg)
+
+		if c.closed {
+			return
+		}
+	}
+}
+
+func (c *Conn) cleanup(ctx context.Context) {
+	c.mu.Lock()
+	wasRegistered := c.registered
+	sessID := c.sessionID
+	nick := c.nick
+	c.closed = true
+	c.mu.Unlock()
+
+	if wasRegistered && sessID > 0 {
+		c.svc.BroadcastQuit(
+			ctx, sessID, nick, "Connection closed",
+		)
+	}
+
+	c.conn.Close() //nolint:errcheck,gosec
+}
+
+// send writes a formatted IRC line to the connection.
+func (c *Conn) send(line string) {
+	_ = c.conn.SetWriteDeadline(
+		time.Now().Add(writeTimeout),
+	)
+
+	_, _ = fmt.Fprintf(c.conn, "%s\r\n", line)
+}
+
+// sendNumeric sends a numeric reply from the server.
+func (c *Conn) sendNumeric(
+	code irc.IRCMessageType,
+	params ...string,
+) {
+	nick := c.nick
+	if nick == "" {
+		nick = "*"
+	}
+
+	allParams := make([]string, 0, 1+len(params))
+	allParams = append(allParams, nick)
+	allParams = append(allParams, params...)
+
+	c.send(FormatMessage(
+		c.serverSfx, code.Code(), allParams...,
+	))
+}
+
+// sendFromServer sends a message from the server.
+func (c *Conn) sendFromServer(
+	command string, params ...string,
+) {
+	c.send(FormatMessage(c.serverSfx, command, params...))
+}
+
+// hostmask returns the client's full hostmask
+// (nick!user@host).
+func (c *Conn) hostmask() string {
+	user := c.username
+	if user == "" {
+		user = c.nick
+	}
+
+	host := c.hostname
+	if host == "" {
+		host = c.remoteIP
+	}
+
+	return c.nick + "!" + user + "@" + host
+}
+
+// handleMessage dispatches a parsed IRC message using
+// the command handler map.
+func (c *Conn) handleMessage(
+	ctx context.Context,
+	msg *Message,
+) {
+	// Before registration, only NICK, USER, PASS, PING,
+	// QUIT, and CAP are accepted.
+	if !c.registered {
+		c.handlePreRegistration(ctx, msg)
+
+		return
+	}
+
+	handler, ok := c.commands[msg.Command]
+	if !ok {
+		c.sendNumeric(
+			irc.ErrUnknownCommand,
+			msg.Command, "Unknown command",
+		)
+
+		return
+	}
+
+	handler(ctx, msg)
+}
+
+// handlePreRegistration handles messages before the
+// connection is registered (NICK+USER received).
+func (c *Conn) handlePreRegistration(
+	ctx context.Context,
+	msg *Message,
+) {
+	switch msg.Command {
+	case irc.CmdPass:
+		if len(msg.Params) < 1 {
+			c.sendNumeric(
+				irc.ErrNeedMoreParams,
+				"PASS", "Not enough parameters",
+			)
+
+			return
+		}
+
+		c.passWord = msg.Params[0]
+	case irc.CmdNick:
+		if len(msg.Params) < 1 {
+			c.sendNumeric(
+				irc.ErrNoNicknameGiven,
+				"No nickname given",
+			)
+
+			return
+		}
+
+		c.nick = msg.Params[0]
+		if len(c.nick) > maxNickLen {
+			c.nick = c.nick[:maxNickLen]
+		}
+
+		c.gotNick = true
+	case irc.CmdUser:
+		if len(msg.Params) < 4 { //nolint:mnd
+			c.sendNumeric(
+				irc.ErrNeedMoreParams,
+				"USER", "Not enough parameters",
+			)
+
+			return
+		}
+
+		c.username = msg.Params[0]
+		c.realname = msg.Params[3]
+		c.gotUser = true
+	case irc.CmdPing:
+		c.handlePing(msg)
+
+		return
+	case irc.CmdQuit:
+		c.handleQuit(msg)
+
+		return
+	case "CAP":
+		c.handleCAP(msg)
+
+		return
+	default:
+		c.sendNumeric(
+			irc.ErrNotRegistered,
+			"You have not registered",
+		)
+
+		return
+	}
+
+	// Try to complete registration once we have both
+	// NICK and USER.
+	if c.gotNick && c.gotUser {
+		c.completeRegistration(ctx)
+	}
+}
+
+// completeRegistration creates a session and sends the
+// welcome burst.
+func (c *Conn) completeRegistration(ctx context.Context) {
+	// Check if nick is valid.
+	if c.nick == "" {
+		c.sendNumeric(
+			irc.ErrNoNicknameGiven, "No nickname given",
+		)
+
+		return
+	}
+
+	// Create session in DB.
+	sessionID, clientID, _, err := c.database.CreateSession(
+		ctx, c.nick, c.username, c.hostname, c.remoteIP,
+	)
+	if err != nil {
+		if strings.Contains(err.Error(), "UNIQUE constraint") ||
+			strings.Contains(err.Error(), "nick") {
+			c.sendNumeric(
+				irc.ErrNicknameInUse,
+				c.nick, "Nickname is already in use",
+			)
+
+			return
+		}
+
+		c.log.Error(
+			"failed to create session", "error", err,
+		)
+		c.send("ERROR :Internal server error")
+		c.closed = true
+
+		return
+	}
+
+	c.mu.Lock()
+	c.sessionID = sessionID
+	c.clientID = clientID
+	c.registered = true
+	c.mu.Unlock()
+
+	// If PASS was provided before registration, set the
+	// session password.
+	if c.passWord != "" && len(c.passWord) >= minPasswordLen {
+		c.setPassword(ctx, c.passWord)
+	}
+
+	// Send welcome burst.
+	c.deliverWelcome()
+	c.deliverLusers(ctx)
+	c.deliverMOTD()
+
+	// Start the message relay goroutine.
+	go c.relayMessages(ctx)
+}
+
+// deliverWelcome sends 001-005 welcome numerics.
+func (c *Conn) deliverWelcome() {
+	c.sendNumeric(irc.RplWelcome, fmt.Sprintf(
+		"Welcome to the %s Network, %s",
+		c.serverSfx, c.hostmask(),
+	))
+	c.sendNumeric(irc.RplYourHost, fmt.Sprintf(
+		"Your host is %s, running version neoirc",
+		c.serverSfx,
+	))
+	c.sendNumeric(
+		irc.RplCreated,
+		"This server was created recently",
+	)
+	c.sendNumeric(
+		irc.RplMyInfo,
+		c.serverSfx, "neoirc", "", "mnst",
+	)
+	c.sendNumeric(
+		irc.RplIsupport,
+		"CHANTYPES=#",
+		"NICKLEN=32",
+		"PREFIX=(ov)@+",
+		"CHANMODES=,,H,mnst",
+		"NETWORK="+c.serverSfx,
+		"are supported by this server",
+	)
+}
+
+// deliverLusers sends 251/252/254/255 server statistics.
+func (c *Conn) deliverLusers(ctx context.Context) {
+	users, _ := c.database.GetUserCount(ctx)
+	opers, _ := c.database.GetOperCount(ctx)
+	channels, _ := c.database.GetChannelCount(ctx)
+
+	c.sendNumeric(irc.RplLuserClient, fmt.Sprintf(
+		"There are %d users and 0 invisible on 1 servers",
+		users,
+	))
+	c.sendNumeric(
+		irc.RplLuserOp,
+		strconv.FormatInt(opers, 10),
+		"operator(s) online",
+	)
+	c.sendNumeric(
+		irc.RplLuserChannels,
+		strconv.FormatInt(channels, 10),
+		"channels formed",
+	)
+	c.sendNumeric(irc.RplLuserMe, fmt.Sprintf(
+		"I have %d clients and 1 servers", users,
+	))
+}
+
+// deliverMOTD sends 375/372/376 MOTD lines.
+func (c *Conn) deliverMOTD() {
+	motd := c.cfg.MOTD
+	if motd == "" {
+		c.sendNumeric(
+			irc.ErrNoMotd, "MOTD File is missing",
+		)
+
+		return
+	}
+
+	c.sendNumeric(irc.RplMotdStart, fmt.Sprintf(
+		"- %s Message of the Day -", c.serverSfx,
+	))
+
+	for _, line := range strings.Split(motd, "\n") {
+		c.sendNumeric(irc.RplMotd, "- "+line)
+	}
+
+	c.sendNumeric(
+		irc.RplEndOfMotd, "End of /MOTD command",
+	)
+}
+
+// setPassword sets a bcrypt password on the session.
+func (c *Conn) setPassword(ctx context.Context, pw string) {
+	// Use the database's auth module to hash and store.
+	err := c.database.SetPassword(ctx, c.sessionID, pw)
+	if err != nil {
+		c.log.Error(
+			"failed to set password", "error", err,
+		)
+	}
+}