feat: add traditional IRC wire protocol listener on configurable port

Add a backward-compatible IRC protocol listener (RFC 1459/2812) that
allows standard IRC clients (irssi, weechat, hexchat, etc.) to connect
directly via TCP.

Key features:
- TCP listener on configurable port (IRC_LISTEN_ADDR env var, e.g. :6667)
- Full IRC wire protocol parsing and formatting
- Connection registration (NICK + USER + optional PASS)
- Channel operations: JOIN, PART, MODE, TOPIC, NAMES, LIST, KICK, INVITE
- Messaging: PRIVMSG, NOTICE (channel and direct)
- Info commands: WHO, WHOIS, LUSERS, MOTD, AWAY
- Operator support: OPER (with configured credentials)
- PING/PONG keepalive
- CAP negotiation (for modern client compatibility)
- Full bridge to HTTP/JSON API (shared DB, broker, sessions)
- Real-time message relay via broker notifications
- Comprehensive test suite (parser + integration tests)

The IRC listener is an optional component — disabled when IRC_LISTEN_ADDR
is empty (the default). The Broker is now an Fx-provided dependency shared
between HTTP handlers and the IRC server.

closes #89

internal/ircserver/relay.go

@@ -0,0 +1,319 @@
+package ircserver
+
+import (
+	"context"
+	"encoding/json"
+	"strings"
+	"time"
+
+	"git.eeqj.de/sneak/neoirc/internal/db"
+	"git.eeqj.de/sneak/neoirc/pkg/irc"
+)
+
+// relayMessages polls the client output queue and delivers
+// IRC-formatted messages to the TCP connection.  It runs
+// in a goroutine for the lifetime of the connection.
+func (c *Conn) relayMessages(ctx context.Context) {
+	// Use a ticker as a fallback; primary wakeup is via
+	// broker notification.
+	ticker := time.NewTicker(pollInterval)
+	defer ticker.Stop()
+
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		default:
+		}
+
+		// Drain any available messages.
+		delivered := c.drainQueue(ctx)
+
+		if delivered {
+			// Tight loop while there are messages.
+			continue
+		}
+
+		// Wait for notification or timeout.
+		waitCh := c.brk.Wait(c.sessionID)
+
+		select {
+		case <-waitCh:
+			// New message notification — loop back.
+		case <-ticker.C:
+			// Periodic check.
+		case <-ctx.Done():
+			c.brk.Remove(c.sessionID, waitCh)
+
+			return
+		}
+	}
+}
+
+const relayPollLimit = 100
+
+// drainQueue polls the output queue and delivers all
+// pending messages.  Returns true if at least one message
+// was delivered.
+func (c *Conn) drainQueue(ctx context.Context) bool {
+	msgs, lastID, err := c.database.PollMessages(
+		ctx, c.clientID, c.lastQueueID, relayPollLimit,
+	)
+	if err != nil {
+		return false
+	}
+
+	if len(msgs) == 0 {
+		return false
+	}
+
+	for i := range msgs {
+		c.deliverIRCMessage(ctx, &msgs[i])
+	}
+
+	if lastID > c.lastQueueID {
+		c.lastQueueID = lastID
+	}
+
+	return true
+}
+
+// deliverIRCMessage converts a db.IRCMessage to wire
+// protocol and sends it.
+//
+//nolint:cyclop // dispatch table
+func (c *Conn) deliverIRCMessage(
+	_ context.Context,
+	msg *db.IRCMessage,
+) {
+	command := msg.Command
+
+	// Decode body as []string for the trailing text.
+	var bodyLines []string
+
+	if msg.Body != nil {
+		_ = json.Unmarshal(msg.Body, &bodyLines)
+	}
+
+	text := ""
+	if len(bodyLines) > 0 {
+		text = bodyLines[0]
+	}
+
+	// Route by command type.
+	switch {
+	case isNumeric(command):
+		c.deliverNumeric(msg, text)
+	case command == irc.CmdPrivmsg || command == irc.CmdNotice:
+		c.deliverTextMessage(msg, command, text)
+	case command == irc.CmdJoin:
+		c.deliverJoin(msg)
+	case command == irc.CmdPart:
+		c.deliverPart(msg, text)
+	case command == irc.CmdNick:
+		c.deliverNickChange(msg, text)
+	case command == irc.CmdQuit:
+		c.deliverQuitMsg(msg, text)
+	case command == irc.CmdTopic:
+		c.deliverTopicChange(msg, text)
+	case command == irc.CmdKick:
+		c.deliverKickMsg(msg, text)
+	case command == "INVITE":
+		c.deliverInviteMsg(msg, text)
+	case command == irc.CmdMode:
+		c.deliverMode(msg, text)
+	case command == irc.CmdPing:
+		// Server-originated PING — reply with PONG.
+		c.sendFromServer("PING", c.serverSfx)
+	default:
+		// Unknown command — deliver as server notice.
+		if text != "" {
+			c.sendFromServer("NOTICE", c.nick, text)
+		}
+	}
+}
+
+// isNumeric returns true if the command is a 3-digit
+// numeric code.
+func isNumeric(cmd string) bool {
+	return len(cmd) == 3 &&
+		cmd[0] >= '0' && cmd[0] <= '9' &&
+		cmd[1] >= '0' && cmd[1] <= '9' &&
+		cmd[2] >= '0' && cmd[2] <= '9'
+}
+
+// deliverNumeric sends a numeric reply.
+func (c *Conn) deliverNumeric(
+	msg *db.IRCMessage,
+	text string,
+) {
+	from := msg.From
+	if from == "" {
+		from = c.serverSfx
+	}
+
+	var params []string
+
+	if msg.Params != nil {
+		_ = json.Unmarshal(msg.Params, &params)
+	}
+
+	allParams := make([]string, 0, 1+len(params)+1)
+	allParams = append(allParams, c.nick)
+	allParams = append(allParams, params...)
+
+	if text != "" {
+		allParams = append(allParams, text)
+	}
+
+	c.send(FormatMessage(from, msg.Command, allParams...))
+}
+
+// deliverTextMessage sends PRIVMSG or NOTICE.
+func (c *Conn) deliverTextMessage(
+	msg *db.IRCMessage,
+	command, text string,
+) {
+	from := msg.From
+	target := msg.To
+
+	// Don't echo our own messages back.
+	if strings.EqualFold(from, c.nick) {
+		return
+	}
+
+	prefix := from
+	if !strings.Contains(prefix, "!") {
+		prefix = from + "!" + from + "@*"
+	}
+
+	c.send(FormatMessage(prefix, command, target, text))
+}
+
+// deliverJoin sends a JOIN notification.
+func (c *Conn) deliverJoin(msg *db.IRCMessage) {
+	// Don't echo our own JOINs (we already sent them
+	// during joinChannel).
+	if strings.EqualFold(msg.From, c.nick) {
+		return
+	}
+
+	prefix := msg.From + "!" + msg.From + "@*"
+	channel := msg.To
+
+	c.send(FormatMessage(prefix, "JOIN", channel))
+}
+
+// deliverPart sends a PART notification.
+func (c *Conn) deliverPart(msg *db.IRCMessage, text string) {
+	if strings.EqualFold(msg.From, c.nick) {
+		return
+	}
+
+	prefix := msg.From + "!" + msg.From + "@*"
+	channel := msg.To
+
+	if text != "" {
+		c.send(FormatMessage(
+			prefix, "PART", channel, text,
+		))
+	} else {
+		c.send(FormatMessage(prefix, "PART", channel))
+	}
+}
+
+// deliverNickChange sends a NICK change notification.
+func (c *Conn) deliverNickChange(
+	msg *db.IRCMessage,
+	newNick string,
+) {
+	if strings.EqualFold(msg.From, c.nick) {
+		return
+	}
+
+	prefix := msg.From + "!" + msg.From + "@*"
+
+	c.send(FormatMessage(prefix, "NICK", newNick))
+}
+
+// deliverQuitMsg sends a QUIT notification.
+func (c *Conn) deliverQuitMsg(
+	msg *db.IRCMessage,
+	text string,
+) {
+	if strings.EqualFold(msg.From, c.nick) {
+		return
+	}
+
+	prefix := msg.From + "!" + msg.From + "@*"
+
+	if text != "" {
+		c.send(FormatMessage(
+			prefix, "QUIT", "Quit: "+text,
+		))
+	} else {
+		c.send(FormatMessage(prefix, "QUIT", "Quit"))
+	}
+}
+
+// deliverTopicChange sends a TOPIC change notification.
+func (c *Conn) deliverTopicChange(
+	msg *db.IRCMessage,
+	text string,
+) {
+	prefix := msg.From + "!" + msg.From + "@*"
+	channel := msg.To
+
+	c.send(FormatMessage(prefix, "TOPIC", channel, text))
+}
+
+// deliverKickMsg sends a KICK notification.
+func (c *Conn) deliverKickMsg(
+	msg *db.IRCMessage,
+	text string,
+) {
+	prefix := msg.From + "!" + msg.From + "@*"
+	channel := msg.To
+
+	var params []string
+
+	if msg.Params != nil {
+		_ = json.Unmarshal(msg.Params, &params)
+	}
+
+	kickTarget := ""
+	if len(params) > 0 {
+		kickTarget = params[0]
+	}
+
+	if kickTarget != "" {
+		c.send(FormatMessage(
+			prefix, "KICK", channel, kickTarget, text,
+		))
+	} else {
+		c.send(FormatMessage(
+			prefix, "KICK", channel, "?", text,
+		))
+	}
+}
+
+// deliverInviteMsg sends an INVITE notification.
+func (c *Conn) deliverInviteMsg(
+	_ *db.IRCMessage,
+	text string,
+) {
+	c.sendFromServer("NOTICE", c.nick, text)
+}
+
+// deliverMode sends a MODE change notification.
+func (c *Conn) deliverMode(
+	msg *db.IRCMessage,
+	text string,
+) {
+	prefix := msg.From + "!" + msg.From + "@*"
+	target := msg.To
+
+	if text != "" {
+		c.send(FormatMessage(prefix, "MODE", target, text))
+	}
+}