Merge branch 'main' into fix/irc-numeric-replies

IRC command handlers now return proper IRC numeric reply codes per
RFC 1459/2812 instead of HTTP status codes:

- 401 ERR_NOSUCHNICK for unknown DM targets
- 403 ERR_NOSUCHCHANNEL for invalid/missing channels
- 411 ERR_NORECIPIENT for missing message recipients
- 412 ERR_NOTEXTTOSEND for missing message body
- 421 ERR_UNKNOWNCOMMAND for unknown/empty commands
- 431 ERR_NONICKNAMEGIVEN for missing nick in NICK command
- 432 ERR_ERRONEUSNICKNAME for invalid nick format
- 433 ERR_NICKNAMEINUSE for taken nicks
- 442 ERR_NOTONCHANNEL for non-member channel actions
- 461 ERR_NEEDMOREPARAMS for missing required parameters

Error responses use the IRC numeric format:
  {"command":"4xx","from":"server","to":"nick","body":["..."],"params":[...]}

HTTP status codes are now reserved for transport-level concerns:
- 400 for malformed HTTP requests (bad JSON)
- 401 for authentication failures
- 500 for internal server errors

Successful message sends changed from 201 to 200 since HTTP
status codes should not encode IRC-level semantics.

internal/handlers/api.go

@@ -28,6 +28,18 @@ const (
 	defaultHistLimit   = 50
 	maxHistLimit       = 500
 	cmdPrivmsg         = "PRIVMSG"
+
+	// IRC numeric reply codes per RFC 1459/2812.
+	ircErrNoSuchNick       = "401"
+	ircErrNoSuchChannel    = "403"
+	ircErrNoRecipient      = "411"
+	ircErrNoTextToSend     = "412"
+	ircErrUnknownCommand   = "421"
+	ircErrNoNicknameGiven  = "431"
+	ircErrErroneusNickname = "432"
+	ircErrNicknameInUse    = "433"
+	ircErrNotOnChannel     = "442"
+	ircErrNeedMoreParams   = "461"
 )
 
 func (hdlr *Handlers) maxBodySize() int64 {
@@ -63,6 +75,43 @@ func (hdlr *Handlers) authSession(
 	return sessionID, clientID, nick, nil
 }
 
+// serverName returns the configured server name or the
+// default "neoirc".
+func (hdlr *Handlers) serverName() string {
+	if hdlr.params.Config.ServerName != "" {
+		return hdlr.params.Config.ServerName
+	}
+
+	return "neoirc"
+}
+
+// respondIRCError sends an IRC numeric error reply as a
+// JSON response with HTTP 200 OK. This is used for errors
+// in IRC command processing (as opposed to HTTP transport
+// errors). The params slice contains IRC-style positional
+// parameters (e.g. the target nick or channel).
+func (hdlr *Handlers) respondIRCError(
+	writer http.ResponseWriter,
+	request *http.Request,
+	nick, numeric, msg string,
+	params ...string,
+) {
+	resp := map[string]any{
+		"command": numeric,
+		"from":    hdlr.serverName(),
+		"to":      nick,
+		"body":    []string{msg},
+	}
+
+	if len(params) > 0 {
+		resp["params"] = params
+	}
+
+	hdlr.respondJSON(
+		writer, request, resp, http.StatusOK,
+	)
+}
+
 func (hdlr *Handlers) requireAuth(
 	writer http.ResponseWriter,
 	request *http.Request,
@@ -226,11 +275,7 @@ func (hdlr *Handlers) deliverMOTD(
 	clientID, sessionID int64,
 ) {
 	motd := hdlr.params.Config.MOTD
-	serverName := hdlr.params.Config.ServerName
-
-	if serverName == "" {
-		serverName = "neoirc"
-	}
+	serverName := hdlr.serverName()
 
 	if motd == "" {
 		return
@@ -557,10 +602,10 @@ func (hdlr *Handlers) HandleSendCommand() http.HandlerFunc {
 		payload.To = strings.TrimSpace(payload.To)
 
 		if payload.Command == "" {
-			hdlr.respondError(
+			hdlr.respondIRCError(
 				writer, request,
-				"command required",
-				http.StatusBadRequest,
+				nick, ircErrUnknownCommand,
+				"No command given",
 			)
 
 			return
@@ -631,10 +676,11 @@ func (hdlr *Handlers) dispatchCommand(
 			},
 			http.StatusOK)
 	default:
-		hdlr.respondError(
+		hdlr.respondIRCError(
 			writer, request,
-			"unknown command: "+command,
-			http.StatusBadRequest,
+			nick, ircErrUnknownCommand,
+			command+" :Unknown command",
+			command,
 		)
 	}
 }
@@ -648,10 +694,10 @@ func (hdlr *Handlers) handlePrivmsg(
 	bodyLines func() []string,
 ) {
 	if target == "" {
-		hdlr.respondError(
+		hdlr.respondIRCError(
 			writer, request,
-			"to field required",
-			http.StatusBadRequest,
+			nick, ircErrNoRecipient,
+			"No recipient given ("+command+")",
 		)
 
 		return
@@ -659,10 +705,10 @@ func (hdlr *Handlers) handlePrivmsg(
 
 	lines := bodyLines()
 	if len(lines) == 0 {
-		hdlr.respondError(
+		hdlr.respondIRCError(
 			writer, request,
-			"body required",
-			http.StatusBadRequest,
+			nick, ircErrNoTextToSend,
+			"No text to send",
 		)
 
 		return
@@ -694,10 +740,11 @@ func (hdlr *Handlers) handleChannelMsg(
 		request.Context(), target,
 	)
 	if err != nil {
-		hdlr.respondError(
+		hdlr.respondIRCError(
 			writer, request,
-			"channel not found",
-			http.StatusNotFound,
+			nick, ircErrNoSuchChannel,
+			"No such channel",
+			target,
 		)
 
 		return
@@ -720,10 +767,11 @@ func (hdlr *Handlers) handleChannelMsg(
 	}
 
 	if !isMember {
-		hdlr.respondError(
+		hdlr.respondIRCError(
 			writer, request,
-			"not a member of this channel",
-			http.StatusForbidden,
+			nick, ircErrNotOnChannel,
+			"You're not on that channel",
+			target,
 		)
 
 		return
@@ -761,7 +809,7 @@ func (hdlr *Handlers) handleChannelMsg(
 
 	hdlr.respondJSON(writer, request,
 		map[string]string{"id": msgUUID, "status": "sent"},
-		http.StatusCreated)
+		http.StatusOK)
 }
 
 func (hdlr *Handlers) handleDirectMsg(
@@ -775,10 +823,11 @@ func (hdlr *Handlers) handleDirectMsg(
 		request.Context(), target,
 	)
 	if err != nil {
-		hdlr.respondError(
+		hdlr.respondIRCError(
 			writer, request,
-			"user not found",
-			http.StatusNotFound,
+			nick, ircErrNoSuchNick,
+			"No such nick/channel",
+			target,
 		)
 
 		return
@@ -805,7 +854,7 @@ func (hdlr *Handlers) handleDirectMsg(
 
 	hdlr.respondJSON(writer, request,
 		map[string]string{"id": msgUUID, "status": "sent"},
-		http.StatusCreated)
+		http.StatusOK)
 }
 
 func (hdlr *Handlers) handleJoin(
@@ -815,10 +864,11 @@ func (hdlr *Handlers) handleJoin(
 	nick, target string,
 ) {
 	if target == "" {
-		hdlr.respondError(
+		hdlr.respondIRCError(
 			writer, request,
-			"to field required",
-			http.StatusBadRequest,
+			nick, ircErrNeedMoreParams,
+			"Not enough parameters",
+			"JOIN",
 		)
 
 		return
@@ -830,10 +880,11 @@ func (hdlr *Handlers) handleJoin(
 	}
 
 	if !validChannelRe.MatchString(channel) {
-		hdlr.respondError(
+		hdlr.respondIRCError(
 			writer, request,
-			"invalid channel name",
-			http.StatusBadRequest,
+			nick, ircErrNoSuchChannel,
+			"No such channel",
+			channel,
 		)
 
 		return
@@ -895,10 +946,11 @@ func (hdlr *Handlers) handlePart(
 	body json.RawMessage,
 ) {
 	if target == "" {
-		hdlr.respondError(
+		hdlr.respondIRCError(
 			writer, request,
-			"to field required",
-			http.StatusBadRequest,
+			nick, ircErrNeedMoreParams,
+			"Not enough parameters",
+			"PART",
 		)
 
 		return
@@ -913,10 +965,11 @@ func (hdlr *Handlers) handlePart(
 		request.Context(), channel,
 	)
 	if err != nil {
-		hdlr.respondError(
+		hdlr.respondIRCError(
 			writer, request,
-			"channel not found",
-			http.StatusNotFound,
+			nick, ircErrNoSuchChannel,
+			"No such channel",
+			channel,
 		)
 
 		return
@@ -967,10 +1020,10 @@ func (hdlr *Handlers) handleNick(
 ) {
 	lines := bodyLines()
 	if len(lines) == 0 {
-		hdlr.respondError(
+		hdlr.respondIRCError(
 			writer, request,
-			"body required (new nick)",
-			http.StatusBadRequest,
+			nick, ircErrNoNicknameGiven,
+			"No nickname given",
 		)
 
 		return
@@ -979,10 +1032,11 @@ func (hdlr *Handlers) handleNick(
 	newNick := strings.TrimSpace(lines[0])
 
 	if !validNickRe.MatchString(newNick) {
-		hdlr.respondError(
+		hdlr.respondIRCError(
 			writer, request,
-			"invalid nick",
-			http.StatusBadRequest,
+			nick, ircErrErroneusNickname,
+			"Erroneous nickname",
+			newNick,
 		)
 
 		return
@@ -1003,10 +1057,11 @@ func (hdlr *Handlers) handleNick(
 	)
 	if err != nil {
 		if strings.Contains(err.Error(), "UNIQUE") {
-			hdlr.respondError(
+			hdlr.respondIRCError(
 				writer, request,
-				"nick already in use",
-				http.StatusConflict,
+				nick, ircErrNicknameInUse,
+				"Nickname is already in use",
+				newNick,
 			)
 
 			return
@@ -1093,10 +1148,11 @@ func (hdlr *Handlers) handleTopic(
 	bodyLines func() []string,
 ) {
 	if target == "" {
-		hdlr.respondError(
+		hdlr.respondIRCError(
 			writer, request,
-			"to field required",
-			http.StatusBadRequest,
+			nick, ircErrNeedMoreParams,
+			"Not enough parameters",
+			"TOPIC",
 		)
 
 		return
@@ -1104,10 +1160,11 @@ func (hdlr *Handlers) handleTopic(
 
 	lines := bodyLines()
 	if len(lines) == 0 {
-		hdlr.respondError(
+		hdlr.respondIRCError(
 			writer, request,
-			"body required (topic text)",
-			http.StatusBadRequest,
+			nick, ircErrNeedMoreParams,
+			"Not enough parameters",
+			"TOPIC",
 		)
 
 		return
@@ -1140,10 +1197,11 @@ func (hdlr *Handlers) handleTopic(
 		request.Context(), channel,
 	)
 	if err != nil {
-		hdlr.respondError(
+		hdlr.respondIRCError(
 			writer, request,
-			"channel not found",
-			http.StatusNotFound,
+			nick, ircErrNoSuchChannel,
+			"No such channel",
+			channel,
 		)
 
 		return

internal/handlers/api_test.go

@@ -668,11 +668,18 @@ func TestJoinMissingTo(t *testing.T) {
 	tserver := newTestServer(t)
 	token := tserver.createSession("joiner3")
 
-	status, _ := tserver.sendCommand(
+	status, result := tserver.sendCommand(
 		token, map[string]any{commandKey: joinCmd},
 	)
-	if status != http.StatusBadRequest {
-		t.Fatalf("expected 400, got %d", status)
+	if status != http.StatusOK {
+		t.Fatalf("expected 200, got %d", status)
+	}
+
+	if result[commandKey] != "461" {
+		t.Fatalf(
+			"expected IRC 461, got %v",
+			result[commandKey],
+		)
 	}
 }
 
@@ -699,9 +706,9 @@ func TestChannelMessage(t *testing.T) {
 			bodyKey:    []string{"hello world"},
 		},
 	)
-	if status != http.StatusCreated {
+	if status != http.StatusOK {
 		t.Fatalf(
-			"expected 201, got %d: %v", status, result,
+			"expected 200, got %d: %v", status, result,
 		)
 	}
 
@@ -728,11 +735,18 @@ func TestMessageMissingBody(t *testing.T) {
 		commandKey: joinCmd, toKey: "#test",
 	})
 
-	status, _ := tserver.sendCommand(token, map[string]any{
+	status, result := tserver.sendCommand(token, map[string]any{
 		commandKey: privmsgCmd, toKey: "#test",
 	})
-	if status != http.StatusBadRequest {
-		t.Fatalf("expected 400, got %d", status)
+	if status != http.StatusOK {
+		t.Fatalf("expected 200, got %d", status)
+	}
+
+	if result[commandKey] != "412" {
+		t.Fatalf(
+			"expected IRC 412, got %v",
+			result[commandKey],
+		)
 	}
 }
 
@@ -740,12 +754,19 @@ func TestMessageMissingTo(t *testing.T) {
 	tserver := newTestServer(t)
 	token := tserver.createSession("noto")
 
-	status, _ := tserver.sendCommand(token, map[string]any{
+	status, result := tserver.sendCommand(token, map[string]any{
 		commandKey: privmsgCmd,
 		bodyKey:    []string{"hello"},
 	})
-	if status != http.StatusBadRequest {
-		t.Fatalf("expected 400, got %d", status)
+	if status != http.StatusOK {
+		t.Fatalf("expected 200, got %d", status)
+	}
+
+	if result[commandKey] != "411" {
+		t.Fatalf(
+			"expected IRC 411, got %v",
+			result[commandKey],
+		)
 	}
 }
 
@@ -760,7 +781,7 @@ func TestNonMemberCannotSend(t *testing.T) {
 	})
 
 	// Alice tries to send without joining.
-	status, _ := tserver.sendCommand(
+	status, result := tserver.sendCommand(
 		aliceToken,
 		map[string]any{
 			commandKey: privmsgCmd,
@@ -768,8 +789,15 @@ func TestNonMemberCannotSend(t *testing.T) {
 			bodyKey:    []string{"sneaky"},
 		},
 	)
-	if status != http.StatusForbidden {
-		t.Fatalf("expected 403, got %d", status)
+	if status != http.StatusOK {
+		t.Fatalf("expected 200, got %d", status)
+	}
+
+	if result[commandKey] != "442" {
+		t.Fatalf(
+			"expected IRC 442, got %v",
+			result[commandKey],
+		)
 	}
 }
 
@@ -786,9 +814,9 @@ func TestDirectMessage(t *testing.T) {
 			bodyKey:    []string{"hey bob"},
 		},
 	)
-	if status != http.StatusCreated {
+	if status != http.StatusOK {
 		t.Fatalf(
-			"expected 201, got %d: %v", status, result,
+			"expected 200, got %d: %v", status, result,
 		)
 	}
 
@@ -818,13 +846,20 @@ func TestDMToNonexistentUser(t *testing.T) {
 	tserver := newTestServer(t)
 	token := tserver.createSession("dmsender")
 
-	status, _ := tserver.sendCommand(token, map[string]any{
+	status, result := tserver.sendCommand(token, map[string]any{
 		commandKey: privmsgCmd,
 		toKey:      "nobody",
 		bodyKey:    []string{"hello?"},
 	})
-	if status != http.StatusNotFound {
-		t.Fatalf("expected 404, got %d", status)
+	if status != http.StatusOK {
+		t.Fatalf("expected 200, got %d", status)
+	}
+
+	if result[commandKey] != "401" {
+		t.Fatalf(
+			"expected IRC 401, got %v",
+			result[commandKey],
+		)
 	}
 }
 
@@ -871,12 +906,19 @@ func TestNickCollision(t *testing.T) {
 
 	tserver.createSession("taken_nick")
 
-	status, _ := tserver.sendCommand(token, map[string]any{
+	status, result := tserver.sendCommand(token, map[string]any{
 		commandKey: "NICK",
 		bodyKey:    []string{"taken_nick"},
 	})
-	if status != http.StatusConflict {
-		t.Fatalf("expected 409, got %d", status)
+	if status != http.StatusOK {
+		t.Fatalf("expected 200, got %d", status)
+	}
+
+	if result[commandKey] != "433" {
+		t.Fatalf(
+			"expected IRC 433, got %v",
+			result[commandKey],
+		)
 	}
 }
 
@@ -884,12 +926,19 @@ func TestNickInvalid(t *testing.T) {
 	tserver := newTestServer(t)
 	token := tserver.createSession("nickval")
 
-	status, _ := tserver.sendCommand(token, map[string]any{
+	status, result := tserver.sendCommand(token, map[string]any{
 		commandKey: "NICK",
 		bodyKey:    []string{"bad nick!"},
 	})
-	if status != http.StatusBadRequest {
-		t.Fatalf("expected 400, got %d", status)
+	if status != http.StatusOK {
+		t.Fatalf("expected 200, got %d", status)
+	}
+
+	if result[commandKey] != "432" {
+		t.Fatalf(
+			"expected IRC 432, got %v",
+			result[commandKey],
+		)
 	}
 }
 
@@ -897,11 +946,18 @@ func TestNickEmptyBody(t *testing.T) {
 	tserver := newTestServer(t)
 	token := tserver.createSession("nicknobody")
 
-	status, _ := tserver.sendCommand(
+	status, result := tserver.sendCommand(
 		token, map[string]any{commandKey: "NICK"},
 	)
-	if status != http.StatusBadRequest {
-		t.Fatalf("expected 400, got %d", status)
+	if status != http.StatusOK {
+		t.Fatalf("expected 200, got %d", status)
+	}
+
+	if result[commandKey] != "431" {
+		t.Fatalf(
+			"expected IRC 431, got %v",
+			result[commandKey],
+		)
 	}
 }
 
@@ -938,12 +994,19 @@ func TestTopicMissingTo(t *testing.T) {
 	tserver := newTestServer(t)
 	token := tserver.createSession("topicnoto")
 
-	status, _ := tserver.sendCommand(token, map[string]any{
+	status, result := tserver.sendCommand(token, map[string]any{
 		commandKey: "TOPIC",
 		bodyKey:    []string{"topic"},
 	})
-	if status != http.StatusBadRequest {
-		t.Fatalf("expected 400, got %d", status)
+	if status != http.StatusOK {
+		t.Fatalf("expected 200, got %d", status)
+	}
+
+	if result[commandKey] != "461" {
+		t.Fatalf(
+			"expected IRC 461, got %v",
+			result[commandKey],
+		)
 	}
 }
 
@@ -955,11 +1018,18 @@ func TestTopicMissingBody(t *testing.T) {
 		commandKey: joinCmd, toKey: "#topictest",
 	})
 
-	status, _ := tserver.sendCommand(token, map[string]any{
+	status, result := tserver.sendCommand(token, map[string]any{
 		commandKey: "TOPIC", toKey: "#topictest",
 	})
-	if status != http.StatusBadRequest {
-		t.Fatalf("expected 400, got %d", status)
+	if status != http.StatusOK {
+		t.Fatalf("expected 200, got %d", status)
+	}
+
+	if result[commandKey] != "461" {
+		t.Fatalf(
+			"expected IRC 461, got %v",
+			result[commandKey],
+		)
 	}
 }
 
@@ -1027,11 +1097,18 @@ func TestUnknownCommand(t *testing.T) {
 	tserver := newTestServer(t)
 	token := tserver.createSession("cmdtest")
 
-	status, _ := tserver.sendCommand(
+	status, result := tserver.sendCommand(
 		token, map[string]any{commandKey: "BOGUS"},
 	)
-	if status != http.StatusBadRequest {
-		t.Fatalf("expected 400, got %d", status)
+	if status != http.StatusOK {
+		t.Fatalf("expected 200, got %d", status)
+	}
+
+	if result[commandKey] != "421" {
+		t.Fatalf(
+			"expected IRC 421, got %v",
+			result[commandKey],
+		)
 	}
 }
 
@@ -1039,11 +1116,18 @@ func TestEmptyCommand(t *testing.T) {
 	tserver := newTestServer(t)
 	token := tserver.createSession("emptycmd")
 
-	status, _ := tserver.sendCommand(
+	status, result := tserver.sendCommand(
 		token, map[string]any{commandKey: ""},
 	)
-	if status != http.StatusBadRequest {
-		t.Fatalf("expected 400, got %d", status)
+	if status != http.StatusOK {
+		t.Fatalf("expected 200, got %d", status)
+	}
+
+	if result[commandKey] != "421" {
+		t.Fatalf(
+			"expected IRC 421, got %v",
+			result[commandKey],
+		)
 	}
 }