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/handlers/api.go

@@ -1528,6 +1528,87 @@ func (hdlr *Handlers) executeJoin(
 		http.StatusOK)
 }
 
+// checkJoinAllowed runs Tier 2 restrictions for an
+// existing channel. Returns true if join is allowed.
+func (hdlr *Handlers) checkJoinAllowed(
+	writer http.ResponseWriter,
+	request *http.Request,
+	sessionID, clientID int64,
+	nick, channel string,
+	chID int64,
+	suppliedKey string,
+) bool {
+	ctx := request.Context()
+
+	// 1. Ban check — prevents banned users from joining.
+	isBanned, banErr := hdlr.params.Database.
+		IsSessionBanned(ctx, chID, sessionID)
+	if banErr == nil && isBanned {
+		hdlr.respondIRCError(
+			writer, request, clientID, sessionID,
+			irc.ErrBannedFromChan, nick,
+			[]string{channel},
+			"Cannot join channel (+b)",
+		)
+
+		return false
+	}
+
+	// 2. Invite-only check (+i).
+	isInviteOnly, ioErr := hdlr.params.Database.
+		IsChannelInviteOnly(ctx, chID)
+	if ioErr == nil && isInviteOnly {
+		hasInvite, invErr := hdlr.params.Database.
+			HasChannelInvite(ctx, chID, sessionID)
+		if invErr != nil || !hasInvite {
+			hdlr.respondIRCError(
+				writer, request, clientID, sessionID,
+				irc.ErrInviteOnlyChan, nick,
+				[]string{channel},
+				"Cannot join channel (+i)",
+			)
+
+			return false
+		}
+	}
+
+	// 3. Channel key check (+k).
+	key, keyErr := hdlr.params.Database.
+		GetChannelKey(ctx, chID)
+	if keyErr == nil && key != "" {
+		if suppliedKey != key {
+			hdlr.respondIRCError(
+				writer, request, clientID, sessionID,
+				irc.ErrBadChannelKey, nick,
+				[]string{channel},
+				"Cannot join channel (+k)",
+			)
+
+			return false
+		}
+	}
+
+	// 4. User limit check (+l).
+	limit, limErr := hdlr.params.Database.
+		GetChannelUserLimit(ctx, chID)
+	if limErr == nil && limit > 0 {
+		count, cntErr := hdlr.params.Database.
+			CountChannelMembers(ctx, chID)
+		if cntErr == nil && count >= int64(limit) {
+			hdlr.respondIRCError(
+				writer, request, clientID, sessionID,
+				irc.ErrChannelIsFull, nick,
+				[]string{channel},
+				"Cannot join channel (+l)",
+			)
+
+			return false
+		}
+	}
+
+	return true
+}
+
 // deliverJoinNumerics sends RPL_TOPIC/RPL_NOTOPIC,
 // RPL_NAMREPLY, and RPL_ENDOFNAMES to the joining client.
 func (hdlr *Handlers) deliverJoinNumerics(
@@ -4010,76 +4091,3 @@ func (hdlr *Handlers) deliverWhoisIdle(
 		"seconds idle, signon time",
 	)
 }
-
-// fanOut inserts a message and enqueues it to all given
-// sessions.
-func (hdlr *Handlers) fanOut(
-	request *http.Request,
-	command, from, target string,
-	body json.RawMessage,
-	meta json.RawMessage,
-	sessionIDs []int64,
-) (string, error) {
-	dbID, msgUUID, err := hdlr.params.Database.InsertMessage(
-		request.Context(), command, from, target,
-		nil, body, meta,
-	)
-	if err != nil {
-		return "", fmt.Errorf("insert message: %w", err)
-	}
-
-	for _, sid := range sessionIDs {
-		enqErr := hdlr.params.Database.EnqueueToSession(
-			request.Context(), sid, dbID,
-		)
-		if enqErr != nil {
-			hdlr.log.Error("enqueue failed",
-				"error", enqErr, "session_id", sid)
-		}
-
-		hdlr.broker.Notify(sid)
-	}
-
-	return msgUUID, nil
-}
-
-// fanOutSilent calls fanOut and discards the UUID.
-func (hdlr *Handlers) fanOutSilent(
-	request *http.Request,
-	command, from, target string,
-	body json.RawMessage,
-	sessionIDs []int64,
-) error {
-	_, err := hdlr.fanOut(
-		request, command, from, target,
-		body, nil, sessionIDs,
-	)
-
-	return err
-}
-
-// requireChannelOp checks if the session is a channel
-// operator and sends ERR_CHANOPRIVSNEEDED if not.
-func (hdlr *Handlers) requireChannelOp(
-	writer http.ResponseWriter,
-	request *http.Request,
-	sessionID, clientID int64,
-	nick, channel string,
-	chID int64,
-) bool {
-	isOp, err := hdlr.params.Database.IsChannelOperator(
-		request.Context(), chID, sessionID,
-	)
-	if err != nil || !isOp {
-		hdlr.respondIRCError(
-			writer, request, clientID, sessionID,
-			irc.ErrChanOpPrivsNeeded, nick,
-			[]string{channel},
-			"You're not channel operator",
-		)
-
-		return false
-	}
-
-	return true
-}

internal/ircserver/commands.go

@@ -179,7 +179,7 @@ func (c *Conn) joinChannel(
 	channel string,
 ) {
 	result, err := c.svc.JoinChannel(
-		ctx, c.sessionID, c.nick, channel, "",
+		ctx, c.sessionID, c.nick, channel,
 	)
 	if err != nil {
 		c.sendIRCError(err)

internal/service/service.go

@@ -140,18 +140,6 @@ func (s *Service) SendChannelMessage(
 		}
 	}
 
-	// Ban check — banned users cannot send messages.
-	isBanned, banErr := s.DB.IsSessionBanned(
-		ctx, chID, sessionID,
-	)
-	if banErr == nil && isBanned {
-		return 0, "", &IRCError{
-			irc.ErrCannotSendToChan,
-			[]string{channel},
-			"Cannot send to channel (+b)",
-		}
-	}
-
 	moderated, _ := s.DB.IsChannelModerated(ctx, chID)
 	if moderated {
 		isOp, _ := s.DB.IsChannelOperator(
@@ -226,7 +214,7 @@ func (s *Service) SendDirectMessage(
 func (s *Service) JoinChannel(
 	ctx context.Context,
 	sessionID int64,
-	nick, channel, suppliedKey string,
+	nick, channel string,
 ) (*JoinResult, error) {
 	chID, err := s.DB.GetOrCreateChannel(ctx, channel)
 	if err != nil {
@@ -238,15 +226,6 @@ func (s *Service) JoinChannel(
 	)
 	isCreator := countErr == nil && memberCount == 0
 
-	if !isCreator {
-		if joinErr := checkJoinRestrictions(
-			ctx, s.DB, chID, sessionID,
-			channel, suppliedKey, memberCount,
-		); joinErr != nil {
-			return nil, joinErr
-		}
-	}
-
 	if isCreator {
 		err = s.DB.JoinChannelAsOperator(
 			ctx, chID, sessionID,
@@ -259,9 +238,6 @@ func (s *Service) JoinChannel(
 		return nil, fmt.Errorf("join channel: %w", err)
 	}
 
-	// Clear invite after successful join.
-	_ = s.DB.ClearChannelInvite(ctx, chID, sessionID)
-
 	memberIDs, _ := s.DB.GetChannelMemberIDs(ctx, chID)
 	body, _ := json.Marshal([]string{channel}) //nolint:errchkjson
 
@@ -675,18 +651,6 @@ func (s *Service) SetChannelFlag(
 		); err != nil {
 			return fmt.Errorf("set topic locked: %w", err)
 		}
-	case 'i':
-		if err := s.DB.SetChannelInviteOnly(
-			ctx, chID, setting,
-		); err != nil {
-			return fmt.Errorf("set invite only: %w", err)
-		}
-	case 's':
-		if err := s.DB.SetChannelSecret(
-			ctx, chID, setting,
-		); err != nil {
-			return fmt.Errorf("set secret: %w", err)
-		}
 	}
 
 	return nil
@@ -779,61 +743,3 @@ func (s *Service) broadcastNickChange(
 		}
 	}
 }
-
-// checkJoinRestrictions validates Tier 2 join conditions:
-// bans, invite-only, channel key, and user limit.
-func checkJoinRestrictions(
-	ctx context.Context,
-	database *db.Database,
-	chID, sessionID int64,
-	channel, suppliedKey string,
-	memberCount int64,
-) error {
-	isBanned, banErr := database.IsSessionBanned(
-		ctx, chID, sessionID,
-	)
-	if banErr == nil && isBanned {
-		return &IRCError{
-			Code:    irc.ErrBannedFromChan,
-			Params:  []string{channel},
-			Message: "Cannot join channel (+b)",
-		}
-	}
-
-	isInviteOnly, ioErr := database.IsChannelInviteOnly(
-		ctx, chID,
-	)
-	if ioErr == nil && isInviteOnly {
-		hasInvite, invErr := database.HasChannelInvite(
-			ctx, chID, sessionID,
-		)
-		if invErr != nil || !hasInvite {
-			return &IRCError{
-				Code:    irc.ErrInviteOnlyChan,
-				Params:  []string{channel},
-				Message: "Cannot join channel (+i)",
-			}
-		}
-	}
-
-	key, keyErr := database.GetChannelKey(ctx, chID)
-	if keyErr == nil && key != "" && suppliedKey != key {
-		return &IRCError{
-			Code:    irc.ErrBadChannelKey,
-			Params:  []string{channel},
-			Message: "Cannot join channel (+k)",
-		}
-	}
-
-	limit, limErr := database.GetChannelUserLimit(ctx, chID)
-	if limErr == nil && limit > 0 &&
-		memberCount >= int64(limit) {
-		return &IRCError{
-			Code:    irc.ErrChannelIsFull,
-			Params:  []string{channel},
-			Message: "Cannot join channel (+l)",
-		}
-	}
-
-	return nil
-}

internal/service/service_test.go

@@ -167,7 +167,7 @@ func TestJoinChannel(t *testing.T) {
 	sid := createSession(ctx, t, env.db, "alice")
 
 	result, err := env.svc.JoinChannel(
-		ctx, sid, "alice", "#general", "",
+		ctx, sid, "alice", "#general",
 	)
 	if err != nil {
 		t.Fatalf("JoinChannel: %v", err)
@@ -185,7 +185,7 @@ func TestJoinChannel(t *testing.T) {
 	sid2 := createSession(ctx, t, env.db, "bob")
 
 	result2, err := env.svc.JoinChannel(
-		ctx, sid2, "bob", "#general", "",
+		ctx, sid2, "bob", "#general",
 	)
 	if err != nil {
 		t.Fatalf("JoinChannel bob: %v", err)
@@ -207,7 +207,7 @@ func TestPartChannel(t *testing.T) {
 	sid := createSession(ctx, t, env.db, "alice")
 
 	_, err := env.svc.JoinChannel(
-		ctx, sid, "alice", "#general", "",
+		ctx, sid, "alice", "#general",
 	)
 	if err != nil {
 		t.Fatalf("JoinChannel: %v", err)
@@ -242,14 +242,14 @@ func TestSendChannelMessage(t *testing.T) {
 	sid2 := createSession(ctx, t, env.db, "bob")
 
 	_, err := env.svc.JoinChannel(
-		ctx, sid1, "alice", "#chat", "",
+		ctx, sid1, "alice", "#chat",
 	)
 	if err != nil {
 		t.Fatalf("join alice: %v", err)
 	}
 
 	_, err = env.svc.JoinChannel(
-		ctx, sid2, "bob", "#chat", "",
+		ctx, sid2, "bob", "#chat",
 	)
 	if err != nil {
 		t.Fatalf("join bob: %v", err)
@@ -293,14 +293,14 @@ func TestBroadcastQuit(t *testing.T) {
 	sid2 := createSession(ctx, t, env.db, "bob")
 
 	_, err := env.svc.JoinChannel(
-		ctx, sid1, "alice", "#room", "",
+		ctx, sid1, "alice", "#room",
 	)
 	if err != nil {
 		t.Fatalf("join alice: %v", err)
 	}
 
 	_, err = env.svc.JoinChannel(
-		ctx, sid2, "bob", "#room", "",
+		ctx, sid2, "bob", "#room",
 	)
 	if err != nil {
 		t.Fatalf("join bob: %v", err)
@@ -326,14 +326,14 @@ func TestSendChannelMessage_Moderated(t *testing.T) {
 	sid2 := createSession(ctx, t, env.db, "bob")
 
 	result, err := env.svc.JoinChannel(
-		ctx, sid1, "alice", "#modchat", "",
+		ctx, sid1, "alice", "#modchat",
 	)
 	if err != nil {
 		t.Fatalf("join alice: %v", err)
 	}
 
 	_, err = env.svc.JoinChannel(
-		ctx, sid2, "bob", "#modchat", "",
+		ctx, sid2, "bob", "#modchat",
 	)
 	if err != nil {
 		t.Fatalf("join bob: %v", err)