refactor: unify user mode processing into shared service layer

Both the HTTP API and IRC wire protocol handlers now call
service.ApplyUserMode/service.QueryUserMode for all user
mode operations. The service layer iterates mode strings
character by character (the correct IRC approach), ensuring
identical behavior regardless of transport.

Removed duplicate mode logic from internal/handlers/utility.go
(buildUserModeString, applyUserModeChange, applyModeChar) and
internal/ircserver/commands.go (buildUmodeString, inline iteration).

Added service-level tests for QueryUserMode, ApplyUserMode
(single-char, multi-char, invalid input, de-oper, +o rejection).

internal/handlers/utility.go

@@ -1,14 +1,14 @@
 package handlers
 
 import (
-	"context"
 	"encoding/json"
-	"fmt"
+	"errors"
 	"net/http"
 	"strings"
 	"time"
 
 	"sneak.berlin/go/neoirc/internal/db"
+	"sneak.berlin/go/neoirc/internal/service"
 	"sneak.berlin/go/neoirc/pkg/irc"
 )
 
@@ -471,7 +471,10 @@ func (hdlr *Handlers) handleWallops(
 }
 
 // handleUserMode handles user mode queries and changes
-// (e.g., MODE nick, MODE nick +w).
+// (e.g., MODE nick, MODE nick +w). Delegates to the
+// shared service.ApplyUserMode / service.QueryUserMode so
+// that mode string processing is identical for both the
+// HTTP API and IRC wire protocol.
 func (hdlr *Handlers) handleUserMode(
 	writer http.ResponseWriter,
 	request *http.Request,
@@ -496,16 +499,46 @@ func (hdlr *Handlers) handleUserMode(
 			return
 		}
 
-		hdlr.applyUserModeChange(
-			writer, request,
-			sessionID, clientID, nick, lines[0],
+		newModes, err := hdlr.svc.ApplyUserMode(
+			ctx, sessionID, lines[0],
 		)
+		if err != nil {
+			var ircErr *service.IRCError
+			if errors.As(err, &ircErr) {
+				hdlr.respondIRCError(
+					writer, request,
+					clientID, sessionID,
+					ircErr.Code, nick, ircErr.Params,
+					ircErr.Message,
+				)
+
+				return
+			}
+
+			hdlr.respondError(
+				writer, request,
+				"internal error",
+				http.StatusInternalServerError,
+			)
+
+			return
+		}
+
+		hdlr.enqueueNumeric(
+			ctx, clientID, irc.RplUmodeIs, nick, nil,
+			newModes,
+		)
+
+		hdlr.broker.Notify(sessionID)
+		hdlr.respondJSON(writer, request,
+			map[string]string{"status": "ok"},
+			http.StatusOK)
 
 		return
 	}
 
-	// Mode query — build the current mode string.
-	modeStr := hdlr.buildUserModeString(ctx, sessionID)
+	// Mode query — delegate to shared service.
+	modeStr := hdlr.svc.QueryUserMode(ctx, sessionID)
 
 	hdlr.enqueueNumeric(
 		ctx, clientID, irc.RplUmodeIs, nick, nil,
@@ -516,144 +549,3 @@ func (hdlr *Handlers) handleUserMode(
 		map[string]string{"status": "ok"},
 		http.StatusOK)
 }
-
-// buildUserModeString constructs the mode string for a
-// user (e.g., "+ow" for oper+wallops).
-func (hdlr *Handlers) buildUserModeString(
-	ctx context.Context,
-	sessionID int64,
-) string {
-	modes := "+"
-
-	isOper, err := hdlr.params.Database.IsSessionOper(
-		ctx, sessionID,
-	)
-	if err == nil && isOper {
-		modes += "o"
-	}
-
-	isWallops, err := hdlr.params.Database.IsSessionWallops(
-		ctx, sessionID,
-	)
-	if err == nil && isWallops {
-		modes += "w"
-	}
-
-	return modes
-}
-
-// applyUserModeChange applies a user mode change string
-// (e.g., "+w", "-w").
-func (hdlr *Handlers) applyUserModeChange(
-	writer http.ResponseWriter,
-	request *http.Request,
-	sessionID, clientID int64,
-	nick, modeStr string,
-) {
-	ctx := request.Context()
-
-	if len(modeStr) < 2 { //nolint:mnd // +/- and mode char
-		hdlr.respondIRCError(
-			writer, request, clientID, sessionID,
-			irc.ErrUmodeUnknownFlag, nick, nil,
-			"Unknown MODE flag",
-		)
-
-		return
-	}
-
-	adding := modeStr[0] == '+'
-	modeChar := modeStr[1:]
-
-	applied, err := hdlr.applyModeChar(
-		ctx, writer, request,
-		sessionID, clientID, nick,
-		modeChar, adding,
-	)
-	if err != nil || !applied {
-		return
-	}
-
-	newModes := hdlr.buildUserModeString(ctx, sessionID)
-
-	hdlr.enqueueNumeric(
-		ctx, clientID, irc.RplUmodeIs, nick, nil,
-		newModes,
-	)
-
-	hdlr.broker.Notify(sessionID)
-	hdlr.respondJSON(writer, request,
-		map[string]string{"status": "ok"},
-		http.StatusOK)
-}
-
-// applyModeChar applies a single user mode character.
-// Returns (applied, error).
-func (hdlr *Handlers) applyModeChar(
-	ctx context.Context,
-	writer http.ResponseWriter,
-	request *http.Request,
-	sessionID, clientID int64,
-	nick, modeChar string,
-	adding bool,
-) (bool, error) {
-	switch modeChar {
-	case "w":
-		err := hdlr.params.Database.SetSessionWallops(
-			ctx, sessionID, adding,
-		)
-		if err != nil {
-			hdlr.log.Error(
-				"set wallops mode failed", "error", err,
-			)
-			hdlr.respondError(
-				writer, request,
-				"internal error",
-				http.StatusInternalServerError,
-			)
-
-			return false, fmt.Errorf(
-				"set wallops: %w", err,
-			)
-		}
-	case "o":
-		// +o cannot be set via MODE, only via OPER.
-		if adding {
-			hdlr.respondIRCError(
-				writer, request, clientID, sessionID,
-				irc.ErrUmodeUnknownFlag, nick, nil,
-				"Unknown MODE flag",
-			)
-
-			return false, nil
-		}
-
-		err := hdlr.params.Database.SetSessionOper(
-			ctx, sessionID, false,
-		)
-		if err != nil {
-			hdlr.log.Error(
-				"clear oper mode failed", "error", err,
-			)
-			hdlr.respondError(
-				writer, request,
-				"internal error",
-				http.StatusInternalServerError,
-			)
-
-			return false, fmt.Errorf(
-				"clear oper: %w", err,
-			)
-		}
-	default:
-		hdlr.respondIRCError(
-			writer, request, clientID, sessionID,
-			irc.ErrUmodeUnknownFlag, nick, nil,
-			"Unknown MODE flag",
-		)
-
-		return false, nil
-	}
-
-	return true, nil
-}