fix(items): stop G-rank Workshop/Cog softlock on missing ACK

MSG_MHF_GET_EXTRA_INFO (0xA6) and MSG_MHF_GET_COG_INFO (0xC3) had
Parse() returning NOT IMPLEMENTED. The dispatch loop treats any Parse
error as a hard drop — no ACK is ever sent, so the client waits
indefinitely and effectively soft-locks when entering the G-rank
Workshop or Master Felyne (Cog) screens.

Fix: parse AckHandle (the only field we can confirm from the protocol)
and respond with doAckBufFail so the client receives a well-formed
buf-type ACK with error code 1. The client's fail branch for these
requests exits cleanly without reading response fields, avoiding the
read-past-EOF crash that an empty success ACK would cause.

The full response format for both packets is still unknown; a complete
implementation requires further RE. The TODO comments mark the gap.

Fixes #180.

docs/unimplemented.md

@@ -15,7 +15,7 @@ All empty handlers carry an inline comment — `// stub: unimplemented` for real
 
 ---
 
-## Unimplemented (70 handlers)
+## Unimplemented (68 handlers)
 
 Grouped by handler file / game subsystem.
 
@@ -77,8 +77,6 @@ Grouped by handler file / game subsystem.
 
 | Handler | Notes |
 |---------|-------|
-| `handleMsgMhfGetExtraInfo` | Fetch supplemental item/character info |
-| `handleMsgMhfGetCogInfo` | Fetch Cog (partner Felyne) information |
 | `handleMsgMhfStampcardPrize` | Claim a stamp card prize |
 
 ### Misc (`handlers_misc.go`)

network/mhfpacket/msg_batch_parse_test.go

@@ -1594,7 +1594,6 @@ func TestBatchParseNotImplemented(t *testing.T) {
 		&MsgSysDispObject{}, &MsgSysHideObject{},
 		&MsgMhfServerCommand{}, &MsgMhfSetLoginwindow{}, &MsgMhfShutClient{},
 		&MsgMhfUpdateGuildcard{},
-		&MsgMhfGetCogInfo{},
 		&MsgCaExchangeItem{},
 	}
 

network/mhfpacket/msg_comprehensive_test.go

@@ -495,6 +495,8 @@ func TestAckHandlePacketsParse(t *testing.T) {
 		{"MsgMhfGetUdSchedule", network.MSG_MHF_GET_UD_SCHEDULE},
 		{"MsgMhfGetUdInfo", network.MSG_MHF_GET_UD_INFO},
 		{"MsgMhfGetKijuInfo", network.MSG_MHF_GET_KIJU_INFO},
+		{"MsgMhfGetExtraInfo", network.MSG_MHF_GET_EXTRA_INFO},
+		{"MsgMhfGetCogInfo", network.MSG_MHF_GET_COG_INFO},
 	}
 
 	ctx := &clientctx.ClientContext{RealClientMode: cfg.ZZ}

network/mhfpacket/msg_mhf_get_cog_info.go

@@ -9,7 +9,9 @@ import (
 )
 
 // MsgMhfGetCogInfo represents the MSG_MHF_GET_COG_INFO
-type MsgMhfGetCogInfo struct{}
+type MsgMhfGetCogInfo struct {
+	AckHandle uint32
+}
 
 // Opcode returns the ID associated with this packet type.
 func (m *MsgMhfGetCogInfo) Opcode() network.PacketID {
@@ -18,7 +20,8 @@ func (m *MsgMhfGetCogInfo) Opcode() network.PacketID {
 
 // Parse parses the packet from binary
 func (m *MsgMhfGetCogInfo) Parse(bf *byteframe.ByteFrame, ctx *clientctx.ClientContext) error {
-	return errors.New("NOT IMPLEMENTED")
+	m.AckHandle = bf.ReadUint32()
+	return nil
 }
 
 // Build builds a binary packet from the current data.

network/mhfpacket/msg_mhf_get_extra_info.go

@@ -9,7 +9,9 @@ import (
 )
 
 // MsgMhfGetExtraInfo represents the MSG_MHF_GET_EXTRA_INFO
-type MsgMhfGetExtraInfo struct{}
+type MsgMhfGetExtraInfo struct {
+	AckHandle uint32
+}
 
 // Opcode returns the ID associated with this packet type.
 func (m *MsgMhfGetExtraInfo) Opcode() network.PacketID {
@@ -18,7 +20,8 @@ func (m *MsgMhfGetExtraInfo) Opcode() network.PacketID {
 
 // Parse parses the packet from binary
 func (m *MsgMhfGetExtraInfo) Parse(bf *byteframe.ByteFrame, ctx *clientctx.ClientContext) error {
-	return errors.New("NOT IMPLEMENTED")
+	m.AckHandle = bf.ReadUint32()
+	return nil
 }
 
 // Build builds a binary packet from the current data.

network/mhfpacket/msg_parse_small_test.go

@@ -25,7 +25,6 @@ func TestParseSmallNotImplemented(t *testing.T) {
 		{"MsgMhfGetCaUniqueID", &MsgMhfGetCaUniqueID{}},
 		{"MsgMhfGetDailyMissionMaster", &MsgMhfGetDailyMissionMaster{}},
 		{"MsgMhfGetDailyMissionPersonal", &MsgMhfGetDailyMissionPersonal{}},
-		{"MsgMhfGetExtraInfo", &MsgMhfGetExtraInfo{}},
 		{"MsgMhfGetRestrictionEvent", &MsgMhfGetRestrictionEvent{}},
 		{"MsgMhfKickExportForce", &MsgMhfKickExportForce{}},
 		{"MsgMhfPaymentAchievement", &MsgMhfPaymentAchievement{}},
@@ -196,6 +195,38 @@ func TestParseSmallEnumerateHouse(t *testing.T) {
 	})
 }
 
+// TestParseSmallGetExtraInfoAndCogInfo tests that MsgMhfGetExtraInfo and
+// MsgMhfGetCogInfo correctly parse their AckHandle field.
+func TestParseSmallGetExtraInfoAndCogInfo(t *testing.T) {
+	ctx := &clientctx.ClientContext{RealClientMode: cfg.ZZ}
+
+	t.Run("GetExtraInfo", func(t *testing.T) {
+		bf := byteframe.NewByteFrame()
+		bf.WriteUint32(0xDEADBEEF)
+		_, _ = bf.Seek(0, io.SeekStart)
+		pkt := &MsgMhfGetExtraInfo{}
+		if err := pkt.Parse(bf, ctx); err != nil {
+			t.Fatalf("Parse() error = %v", err)
+		}
+		if pkt.AckHandle != 0xDEADBEEF {
+			t.Errorf("AckHandle = 0x%X, want 0xDEADBEEF", pkt.AckHandle)
+		}
+	})
+
+	t.Run("GetCogInfo", func(t *testing.T) {
+		bf := byteframe.NewByteFrame()
+		bf.WriteUint32(0xCAFEBABE)
+		_, _ = bf.Seek(0, io.SeekStart)
+		pkt := &MsgMhfGetCogInfo{}
+		if err := pkt.Parse(bf, ctx); err != nil {
+			t.Fatalf("Parse() error = %v", err)
+		}
+		if pkt.AckHandle != 0xCAFEBABE {
+			t.Errorf("AckHandle = 0x%X, want 0xCAFEBABE", pkt.AckHandle)
+		}
+	})
+}
+
 // TestParseSmallNotImplementedDoesNotPanic ensures that calling Parse on NOT IMPLEMENTED
 // packets returns an error and does not panic.
 func TestParseSmallNotImplementedDoesNotPanic(t *testing.T) {

server/channelserver/handlers_items.go

@@ -55,7 +55,11 @@ func handleMsgMhfEnumerateOrder(s *Session, p mhfpacket.MHFPacket) {
 	stubEnumerateNoResults(s, pkt.AckHandle)
 }
 
-func handleMsgMhfGetExtraInfo(s *Session, p mhfpacket.MHFPacket) {} // stub: unimplemented
+func handleMsgMhfGetExtraInfo(s *Session, p mhfpacket.MHFPacket) {
+	pkt := p.(*mhfpacket.MsgMhfGetExtraInfo)
+	// TODO: response structure unknown; fail ACK prevents softlock without misleading client
+	doAckBufFail(s, pkt.AckHandle, nil)
+}
 
 func userGetItems(s *Session) []mhfitem.MHFItemStack {
 	var items []mhfitem.MHFItemStack
@@ -91,7 +95,11 @@ func handleMsgMhfUpdateUnionItem(s *Session, p mhfpacket.MHFPacket) {
 	doAckSimpleSucceed(s, pkt.AckHandle, make([]byte, 4))
 }
 
-func handleMsgMhfGetCogInfo(s *Session, p mhfpacket.MHFPacket) {} // stub: unimplemented
+func handleMsgMhfGetCogInfo(s *Session, p mhfpacket.MHFPacket) {
+	pkt := p.(*mhfpacket.MsgMhfGetCogInfo)
+	// TODO: response structure unknown; fail ACK prevents softlock without misleading client
+	doAckBufFail(s, pkt.AckHandle, nil)
+}
 
 func handleMsgMhfCheckWeeklyStamp(s *Session, p mhfpacket.MHFPacket) {
 	pkt := p.(*mhfpacket.MsgMhfCheckWeeklyStamp)

server/channelserver/handlers_items_test.go

@@ -494,13 +494,8 @@ func TestHandleMsgMhfGetExtraInfo(t *testing.T) {
 	server := createMockServer()
 	session := createMockSession(1, server)
 
-	defer func() {
-		if r := recover(); r != nil {
-			t.Errorf("handleMsgMhfGetExtraInfo panicked: %v", r)
-		}
-	}()
-
-	handleMsgMhfGetExtraInfo(session, nil)
+	pkt := &mhfpacket.MsgMhfGetExtraInfo{AckHandle: 1}
+	handleMsgMhfGetExtraInfo(session, pkt)
 }
 
 func TestHandleMsgMhfTransferItem(t *testing.T) {

server/channelserver/handlers_misc_test.go

@@ -336,13 +336,8 @@ func TestHandleMsgMhfGetCogInfo(t *testing.T) {
 	server := createMockServer()
 	session := createMockSession(1, server)
 
-	defer func() {
-		if r := recover(); r != nil {
-			t.Errorf("handleMsgMhfGetCogInfo panicked: %v", r)
-		}
-	}()
-
-	handleMsgMhfGetCogInfo(session, nil)
+	pkt := &mhfpacket.MsgMhfGetCogInfo{AckHandle: 1}
+	handleMsgMhfGetCogInfo(session, pkt)
 }
 
 // Additional handler tests for coverage
@@ -1032,7 +1027,7 @@ func TestEmptyHandlers_MiscFiles_Misc(t *testing.T) {
 		name string
 		fn   func()
 	}{
-		{"handleMsgMhfGetCogInfo", func() { handleMsgMhfGetCogInfo(session, nil) }},
+
 		{"handleMsgMhfUseUdShopCoin", func() { handleMsgMhfUseUdShopCoin(session, nil) }},
 		{"handleMsgMhfGetDailyMissionMaster", func() { handleMsgMhfGetDailyMissionMaster(session, nil) }},
 		{"handleMsgMhfGetDailyMissionPersonal", func() { handleMsgMhfGetDailyMissionPersonal(session, nil) }},

server/channelserver/handlers_session_test.go

@@ -1079,7 +1079,6 @@ func TestEmptyHandlers_HandlersGo(t *testing.T) {
 		{"handleMsgSysEnumuser", func() { handleMsgSysEnumuser(session, nil) }},
 		{"handleMsgSysInfokyserver", func() { handleMsgSysInfokyserver(session, nil) }},
 		{"handleMsgMhfGetCaUniqueID", func() { handleMsgMhfGetCaUniqueID(session, nil) }},
-		{"handleMsgMhfGetExtraInfo", func() { handleMsgMhfGetExtraInfo(session, nil) }},
 		{"handleMsgSysSetStatus", func() { handleMsgSysSetStatus(session, nil) }},
 		{"handleMsgMhfStampcardPrize", func() { handleMsgMhfStampcardPrize(session, nil) }},
 		{"handleMsgMhfKickExportForce", func() { handleMsgMhfKickExportForce(session, nil) }},
@@ -1118,7 +1117,6 @@ func TestEmptyHandlers_Concurrent(t *testing.T) {
 		handleMsgSysEnumuser,
 		handleMsgSysInfokyserver,
 		handleMsgMhfGetCaUniqueID,
-		handleMsgMhfGetExtraInfo,
 		handleMsgSysSetStatus,
 		handleMsgSysDeleteObject,
 		handleMsgSysRotateObject,

server/channelserver/handlers_simple_test.go

@@ -290,8 +290,6 @@ func TestEmptyHandlers_NoDb(t *testing.T) {
 		{"handleMsgSysEnumuser", handleMsgSysEnumuser},
 		{"handleMsgSysInfokyserver", handleMsgSysInfokyserver},
 		{"handleMsgMhfGetCaUniqueID", handleMsgMhfGetCaUniqueID},
-		{"handleMsgMhfGetExtraInfo", handleMsgMhfGetExtraInfo},
-		{"handleMsgMhfGetCogInfo", handleMsgMhfGetCogInfo},
 		{"handleMsgMhfStampcardPrize", handleMsgMhfStampcardPrize},
 		{"handleMsgMhfKickExportForce", handleMsgMhfKickExportForce},
 		{"handleMsgSysSetStatus", handleMsgSysSetStatus},