refactor(mail): extract mail logic into MailService

Introduce MailService as a convenience layer between handlers/services
and MailRepo. Provides Send, SendSystem, SendGuildInvite, and
BroadcastToGuild methods that encapsulate the boolean flag combinations.

GuildService now depends on MailService instead of MailRepo directly,
simplifying its mail-sending calls from verbose SendMail(..., false, true)
to clean SendSystem(recipientID, subject, body).

Guild mail broadcast logic moved from handleMsgMhfSendMail into
MailService.BroadcastToGuild.

server/channelserver/handlers_mail.go

@@ -194,31 +194,21 @@ func handleMsgMhfOprtMail(s *Session, p mhfpacket.MHFPacket) {
 func handleMsgMhfSendMail(s *Session, p mhfpacket.MHFPacket) {
 	pkt := p.(*mhfpacket.MsgMhfSendMail)
 
-	if pkt.RecipientID == 0 { // Guild mail
+	if pkt.RecipientID == 0 { // Guild mail broadcast
 		g, err := s.server.guildRepo.GetByCharID(s.charID)
 		if err != nil {
 			s.logger.Error("Failed to get guild info for mail")
 			doAckSimpleSucceed(s, pkt.AckHandle, make([]byte, 4))
 			return
 		}
-		gm, err := s.server.guildRepo.GetMembers(g.ID, false)
-		if err != nil {
-			s.logger.Error("Failed to get guild members for mail")
+		if err := s.server.mailService.BroadcastToGuild(s.charID, g.ID, pkt.Subject, pkt.Body); err != nil {
+			s.logger.Error("Failed to broadcast guild mail", zap.Error(err))
 			doAckSimpleSucceed(s, pkt.AckHandle, make([]byte, 4))
 			return
 		}
-		for i := 0; i < len(gm); i++ {
-			err := s.server.mailRepo.SendMail(s.charID, gm[i].CharID, pkt.Subject, pkt.Body, 0, 0, false, false)
-			if err != nil {
-				s.logger.Error("Failed to send mail")
-				doAckSimpleSucceed(s, pkt.AckHandle, make([]byte, 4))
-				return
-			}
-		}
 	} else {
-		err := s.server.mailRepo.SendMail(s.charID, pkt.RecipientID, pkt.Subject, pkt.Body, pkt.ItemID, pkt.Quantity, false, false)
-		if err != nil {
-			s.logger.Error("Failed to send mail")
+		if err := s.server.mailService.Send(s.charID, pkt.RecipientID, pkt.Subject, pkt.Body, pkt.ItemID, pkt.Quantity); err != nil {
+			s.logger.Error("Failed to send mail", zap.Error(err))
 		}
 	}
 	doAckSimpleSucceed(s, pkt.AckHandle, make([]byte, 4))

server/channelserver/handlers_mail_test.go

@@ -386,6 +386,7 @@ func TestHandleMsgMhfSendMail_Direct(t *testing.T) {
 	server := createMockServer()
 	mock := &mockMailRepo{}
 	server.mailRepo = mock
+	ensureMailService(server)
 	session := createMockSession(1, server)
 
 	pkt := &mhfpacket.MsgMhfSendMail{
@@ -436,6 +437,7 @@ func TestHandleMsgMhfSendMail_Guild(t *testing.T) {
 	}
 	server.mailRepo = mailMock
 	server.guildRepo = guildMock
+	ensureMailService(server)
 	session := createMockSession(1, server)
 
 	pkt := &mhfpacket.MsgMhfSendMail{
@@ -470,6 +472,7 @@ func TestHandleMsgMhfSendMail_GuildNotFound(t *testing.T) {
 	guildMock := &mockGuildRepoForMail{getErr: errNotFound}
 	server.mailRepo = mailMock
 	server.guildRepo = guildMock
+	ensureMailService(server)
 	session := createMockSession(1, server)
 
 	pkt := &mhfpacket.MsgMhfSendMail{

server/channelserver/repo_mocks_test.go

@@ -265,9 +265,10 @@ func (m *mockGoocooRepo) SaveSlot(_ uint32, slot uint32, data []byte) error {
 // --- mockGuildRepo (minimal, for SendMail guild path) ---
 
 type mockGuildRepoForMail struct {
-	guild   *Guild
-	members []*GuildMember
-	getErr  error
+	guild         *Guild
+	members       []*GuildMember
+	getErr        error
+	getMembersErr error
 }
 
 func (m *mockGuildRepoForMail) GetByCharID(_ uint32) (*Guild, error) {
@@ -278,6 +279,9 @@ func (m *mockGuildRepoForMail) GetByCharID(_ uint32) (*Guild, error) {
 }
 
 func (m *mockGuildRepoForMail) GetMembers(_ uint32, _ bool) ([]*GuildMember, error) {
+	if m.getMembersErr != nil {
+		return nil, m.getMembersErr
+	}
 	return m.members, nil
 }
 

server/channelserver/svc_guild.go

@@ -84,16 +84,16 @@ type AnswerScoutResult struct {
 // GuildService encapsulates guild business logic, sitting between handlers and repos.
 type GuildService struct {
 	guildRepo GuildRepo
-	mailRepo  MailRepo
+	mailSvc   *MailService
 	charRepo  CharacterRepo
 	logger    *zap.Logger
 }
 
 // NewGuildService creates a new GuildService.
-func NewGuildService(gr GuildRepo, mr MailRepo, cr CharacterRepo, log *zap.Logger) *GuildService {
+func NewGuildService(gr GuildRepo, ms *MailService, cr CharacterRepo, log *zap.Logger) *GuildService {
 	return &GuildService{
 		guildRepo: gr,
-		mailRepo:  mr,
+		mailSvc:   ms,
 		charRepo:  cr,
 		logger:    log,
 	}
@@ -148,7 +148,7 @@ func (svc *GuildService) OperateMember(actorCharID, targetCharID uint32, action
 	}
 
 	// Send mail best-effort
-	if mailErr := svc.mailRepo.SendMail(mail.SenderID, mail.RecipientID, mail.Subject, mail.Body, 0, 0, false, true); mailErr != nil {
+	if mailErr := svc.mailSvc.SendSystem(mail.RecipientID, mail.Subject, mail.Body); mailErr != nil {
 		svc.logger.Warn("Failed to send guild member operation mail", zap.Error(mailErr))
 	}
 
@@ -255,9 +255,8 @@ func (svc *GuildService) Leave(charID, guildID uint32, isApplicant bool, guildNa
 	}
 
 	// Best-effort withdrawal notification
-	if err := svc.mailRepo.SendMail(0, charID, "Withdrawal",
-		fmt.Sprintf("You have withdrawn from 「%s」.", guildName),
-		0, 0, false, true); err != nil {
+	if err := svc.mailSvc.SendSystem(charID, "Withdrawal",
+		fmt.Sprintf("You have withdrawn from 「%s」.", guildName)); err != nil {
 		svc.logger.Warn("Failed to send guild withdrawal notification", zap.Error(err))
 	}
 
@@ -342,7 +341,7 @@ func (svc *GuildService) AnswerScout(charID, leaderID uint32, accept bool, strin
 
 	// Send mails best-effort
 	for _, m := range mails {
-		if mailErr := svc.mailRepo.SendMail(m.SenderID, m.RecipientID, m.Subject, m.Body, 0, 0, false, true); mailErr != nil {
+		if mailErr := svc.mailSvc.SendSystem(m.RecipientID, m.Subject, m.Body); mailErr != nil {
 			svc.logger.Warn("Failed to send guild scout response mail", zap.Error(mailErr))
 		}
 	}

server/channelserver/svc_guild_test.go

@@ -7,9 +7,15 @@ import (
 	"go.uber.org/zap"
 )
 
+func newTestMailService(mr MailRepo, gr GuildRepo) *MailService {
+	logger, _ := zap.NewDevelopment()
+	return NewMailService(mr, gr, logger)
+}
+
 func newTestGuildService(gr GuildRepo, mr MailRepo) *GuildService {
 	logger, _ := zap.NewDevelopment()
-	return NewGuildService(gr, mr, nil, logger)
+	ms := newTestMailService(mr, gr)
+	return NewGuildService(gr, ms, nil, logger)
 }
 
 func TestGuildService_OperateMember(t *testing.T) {

server/channelserver/svc_mail.go

@@ -0,0 +1,55 @@
+package channelserver
+
+import (
+	"fmt"
+
+	"go.uber.org/zap"
+)
+
+// MailService encapsulates mail-sending business logic, sitting between
+// handlers/services and the MailRepo. It provides convenient methods for
+// common mail patterns (system notifications, guild broadcasts, player mail)
+// so callers don't need to specify boolean flags directly.
+type MailService struct {
+	mailRepo  MailRepo
+	guildRepo GuildRepo
+	logger    *zap.Logger
+}
+
+// NewMailService creates a new MailService.
+func NewMailService(mr MailRepo, gr GuildRepo, log *zap.Logger) *MailService {
+	return &MailService{
+		mailRepo:  mr,
+		guildRepo: gr,
+		logger:    log,
+	}
+}
+
+// Send sends a player-to-player mail with an optional item attachment.
+func (svc *MailService) Send(senderID, recipientID uint32, subject, body string, itemID, quantity uint16) error {
+	return svc.mailRepo.SendMail(senderID, recipientID, subject, body, itemID, quantity, false, false)
+}
+
+// SendSystem sends a system notification mail (no item, flagged as system message).
+func (svc *MailService) SendSystem(recipientID uint32, subject, body string) error {
+	return svc.mailRepo.SendMail(0, recipientID, subject, body, 0, 0, false, true)
+}
+
+// SendGuildInvite sends a guild invitation mail (flagged as guild invite).
+func (svc *MailService) SendGuildInvite(senderID, recipientID uint32, subject, body string) error {
+	return svc.mailRepo.SendMail(senderID, recipientID, subject, body, 0, 0, true, false)
+}
+
+// BroadcastToGuild sends a mail from senderID to all members of the specified guild.
+func (svc *MailService) BroadcastToGuild(senderID, guildID uint32, subject, body string) error {
+	members, err := svc.guildRepo.GetMembers(guildID, false)
+	if err != nil {
+		return fmt.Errorf("get guild members for broadcast: %w", err)
+	}
+	for _, m := range members {
+		if err := svc.mailRepo.SendMail(senderID, m.CharID, subject, body, 0, 0, false, false); err != nil {
+			return fmt.Errorf("send guild broadcast to char %d: %w", m.CharID, err)
+		}
+	}
+	return nil
+}

server/channelserver/svc_mail_test.go

@@ -0,0 +1,162 @@
+package channelserver
+
+import (
+	"errors"
+	"testing"
+
+	"go.uber.org/zap"
+)
+
+func TestMailService_Send(t *testing.T) {
+	mock := &mockMailRepo{}
+	logger, _ := zap.NewDevelopment()
+	svc := NewMailService(mock, nil, logger)
+
+	err := svc.Send(1, 42, "Hello", "World", 500, 3)
+	if err != nil {
+		t.Fatalf("Unexpected error: %v", err)
+	}
+	if len(mock.sentMails) != 1 {
+		t.Fatalf("Expected 1 mail, got %d", len(mock.sentMails))
+	}
+	m := mock.sentMails[0]
+	if m.senderID != 1 {
+		t.Errorf("SenderID = %d, want 1", m.senderID)
+	}
+	if m.recipientID != 42 {
+		t.Errorf("RecipientID = %d, want 42", m.recipientID)
+	}
+	if m.subject != "Hello" {
+		t.Errorf("Subject = %q, want %q", m.subject, "Hello")
+	}
+	if m.itemID != 500 {
+		t.Errorf("ItemID = %d, want 500", m.itemID)
+	}
+	if m.itemAmount != 3 {
+		t.Errorf("Quantity = %d, want 3", m.itemAmount)
+	}
+	if m.isGuildInvite || m.isSystemMessage {
+		t.Error("Should not be guild invite or system message")
+	}
+}
+
+func TestMailService_Send_Error(t *testing.T) {
+	mock := &mockMailRepo{sendErr: errors.New("db fail")}
+	logger, _ := zap.NewDevelopment()
+	svc := NewMailService(mock, nil, logger)
+
+	err := svc.Send(1, 42, "Hello", "World", 0, 0)
+	if err == nil {
+		t.Fatal("Expected error, got nil")
+	}
+}
+
+func TestMailService_SendSystem(t *testing.T) {
+	mock := &mockMailRepo{}
+	logger, _ := zap.NewDevelopment()
+	svc := NewMailService(mock, nil, logger)
+
+	err := svc.SendSystem(42, "System Alert", "Something happened")
+	if err != nil {
+		t.Fatalf("Unexpected error: %v", err)
+	}
+	if len(mock.sentMails) != 1 {
+		t.Fatalf("Expected 1 mail, got %d", len(mock.sentMails))
+	}
+	m := mock.sentMails[0]
+	if m.senderID != 0 {
+		t.Errorf("SenderID = %d, want 0 (system)", m.senderID)
+	}
+	if m.recipientID != 42 {
+		t.Errorf("RecipientID = %d, want 42", m.recipientID)
+	}
+	if !m.isSystemMessage {
+		t.Error("Should be system message")
+	}
+	if m.isGuildInvite {
+		t.Error("Should not be guild invite")
+	}
+}
+
+func TestMailService_SendGuildInvite(t *testing.T) {
+	mock := &mockMailRepo{}
+	logger, _ := zap.NewDevelopment()
+	svc := NewMailService(mock, nil, logger)
+
+	err := svc.SendGuildInvite(1, 42, "Invite", "Join us")
+	if err != nil {
+		t.Fatalf("Unexpected error: %v", err)
+	}
+	if len(mock.sentMails) != 1 {
+		t.Fatalf("Expected 1 mail, got %d", len(mock.sentMails))
+	}
+	m := mock.sentMails[0]
+	if !m.isGuildInvite {
+		t.Error("Should be guild invite")
+	}
+	if m.isSystemMessage {
+		t.Error("Should not be system message")
+	}
+}
+
+func TestMailService_BroadcastToGuild(t *testing.T) {
+	mailMock := &mockMailRepo{}
+	guildMock := &mockGuildRepoForMail{
+		members: []*GuildMember{
+			{CharID: 100},
+			{CharID: 200},
+			{CharID: 300},
+		},
+	}
+	logger, _ := zap.NewDevelopment()
+	svc := NewMailService(mailMock, guildMock, logger)
+
+	err := svc.BroadcastToGuild(1, 10, "News", "Update")
+	if err != nil {
+		t.Fatalf("Unexpected error: %v", err)
+	}
+	if len(mailMock.sentMails) != 3 {
+		t.Fatalf("Expected 3 mails, got %d", len(mailMock.sentMails))
+	}
+	recipients := map[uint32]bool{}
+	for _, m := range mailMock.sentMails {
+		recipients[m.recipientID] = true
+		if m.senderID != 1 {
+			t.Errorf("SenderID = %d, want 1", m.senderID)
+		}
+	}
+	if !recipients[100] || !recipients[200] || !recipients[300] {
+		t.Errorf("Expected recipients 100, 200, 300, got %v", recipients)
+	}
+}
+
+func TestMailService_BroadcastToGuild_GetMembersError(t *testing.T) {
+	mailMock := &mockMailRepo{}
+	guildMock := &mockGuildRepoForMail{getMembersErr: errors.New("db fail")}
+	logger, _ := zap.NewDevelopment()
+	svc := NewMailService(mailMock, guildMock, logger)
+
+	err := svc.BroadcastToGuild(1, 10, "News", "Update")
+	if err == nil {
+		t.Fatal("Expected error, got nil")
+	}
+	if len(mailMock.sentMails) != 0 {
+		t.Errorf("No mails should be sent on error, got %d", len(mailMock.sentMails))
+	}
+}
+
+func TestMailService_BroadcastToGuild_SendError(t *testing.T) {
+	mailMock := &mockMailRepo{sendErr: errors.New("db fail")}
+	guildMock := &mockGuildRepoForMail{
+		members: []*GuildMember{
+			{CharID: 100},
+		},
+	}
+	logger, _ := zap.NewDevelopment()
+	svc := NewMailService(mailMock, guildMock, logger)
+
+	err := svc.BroadcastToGuild(1, 10, "News", "Update")
+	if err == nil {
+		t.Fatal("Expected error, got nil")
+	}
+}

server/channelserver/sys_channel_server.go

@@ -43,44 +43,45 @@ type Config struct {
 // own locks internally and may be acquired at any point.
 type Server struct {
 	sync.Mutex
-	Registry        ChannelRegistry
-	ID              uint16
-	GlobalID        string
-	IP              string
-	Port            uint16
-	logger          *zap.Logger
-	db              *sqlx.DB
-	charRepo        CharacterRepo
-	guildRepo       GuildRepo
-	userRepo        UserRepo
-	gachaRepo       GachaRepo
-	houseRepo       HouseRepo
-	festaRepo       FestaRepo
-	towerRepo       TowerRepo
-	rengokuRepo     RengokuRepo
-	mailRepo        MailRepo
-	stampRepo       StampRepo
-	distRepo        DistributionRepo
-	sessionRepo     SessionRepo
-	eventRepo       EventRepo
-	achievementRepo AchievementRepo
-	shopRepo        ShopRepo
-	cafeRepo        CafeRepo
-	goocooRepo      GoocooRepo
-	divaRepo        DivaRepo
-	miscRepo        MiscRepo
-	scenarioRepo    ScenarioRepo
-	mercenaryRepo   MercenaryRepo
+	Registry           ChannelRegistry
+	ID                 uint16
+	GlobalID           string
+	IP                 string
+	Port               uint16
+	logger             *zap.Logger
+	db                 *sqlx.DB
+	charRepo           CharacterRepo
+	guildRepo          GuildRepo
+	userRepo           UserRepo
+	gachaRepo          GachaRepo
+	houseRepo          HouseRepo
+	festaRepo          FestaRepo
+	towerRepo          TowerRepo
+	rengokuRepo        RengokuRepo
+	mailRepo           MailRepo
+	stampRepo          StampRepo
+	distRepo           DistributionRepo
+	sessionRepo        SessionRepo
+	eventRepo          EventRepo
+	achievementRepo    AchievementRepo
+	shopRepo           ShopRepo
+	cafeRepo           CafeRepo
+	goocooRepo         GoocooRepo
+	divaRepo           DivaRepo
+	miscRepo           MiscRepo
+	scenarioRepo       ScenarioRepo
+	mercenaryRepo      MercenaryRepo
+	mailService        *MailService
 	guildService       *GuildService
 	achievementService *AchievementService
 	gachaService       *GachaService
-	erupeConfig     *cfg.Config
-	acceptConns     chan net.Conn
-	deleteConns     chan net.Conn
-	sessions        map[net.Conn]*Session
-	listener        net.Listener // Listener that is created when Server.Start is called.
-	isShuttingDown  bool
-	done            chan struct{} // Closed on Shutdown to wake background goroutines.
+	erupeConfig        *cfg.Config
+	acceptConns        chan net.Conn
+	deleteConns        chan net.Conn
+	sessions           map[net.Conn]*Session
+	listener           net.Listener // Listener that is created when Server.Start is called.
+	isShuttingDown     bool
+	done               chan struct{} // Closed on Shutdown to wake background goroutines.
 
 	stages StageMap
 
@@ -156,7 +157,8 @@ func NewServer(config *Config) *Server {
 	s.scenarioRepo = NewScenarioRepository(config.DB)
 	s.mercenaryRepo = NewMercenaryRepository(config.DB)
 
-	s.guildService = NewGuildService(s.guildRepo, s.mailRepo, s.charRepo, s.logger)
+	s.mailService = NewMailService(s.mailRepo, s.guildRepo, s.logger)
+	s.guildService = NewGuildService(s.guildRepo, s.mailService, s.charRepo, s.logger)
 	s.achievementService = NewAchievementService(s.achievementRepo, s.logger)
 	s.gachaService = NewGachaService(s.gachaRepo, s.userRepo, s.charRepo, s.logger, config.ErupeConfig.GameplayOptions.MaximumNP)
 

server/channelserver/test_helpers_test.go

@@ -55,10 +55,17 @@ func createMockServer() *Server {
 	return s
 }
 
+// ensureMailService wires the MailService from the server's current repos.
+// Call this after setting mailRepo and guildRepo on the mock server.
+func ensureMailService(s *Server) {
+	s.mailService = NewMailService(s.mailRepo, s.guildRepo, s.logger)
+}
+
 // ensureGuildService wires the GuildService from the server's current repos.
 // Call this after setting guildRepo, mailRepo, and charRepo on the mock server.
 func ensureGuildService(s *Server) {
-	s.guildService = NewGuildService(s.guildRepo, s.mailRepo, s.charRepo, s.logger)
+	ensureMailService(s)
+	s.guildService = NewGuildService(s.guildRepo, s.mailService, s.charRepo, s.logger)
 }
 
 // ensureAchievementService wires the AchievementService from the server's current repos.