feat: split client tooling and add OAuth server login

go/internal/server/feature/feature.go

@@ -0,0 +1,100 @@
+// Package feature contains deliberately small, stateless protocol handlers.
+//
+// These endpoints were observed to return an empty protobuf for a new local
+// account. Keeping that fact here (rather than treating every unknown route
+// as successful) lets the session dispatcher remain fail-closed.
+package feature
+
+import (
+	"errors"
+	"fmt"
+
+	"bd2server/internal/server/wire"
+)
+
+// ErrInvalidRequest means a known endpoint was sent a malformed request.
+var ErrInvalidRequest = errors.New("feature: invalid protobuf request")
+
+// emptyResponses is the stateless subset of the 2.34.13 new-player batch whose
+// successful response protobuf has zero bytes. Stateful routes leave this map
+// as soon as their owning domain persists them. Packet codes are protocol
+// values, not ordinals derived from the request or response order.
+var emptyResponses = map[string]int{
+	"/AvatarShopWishListInfo":          470,
+	"/CafeteriaInfo":                   351,
+	"/CashBonusInfo":                   588,
+	"/CharPartnerInfo":                 65,
+	"/CommunityRewardInfo":             289,
+	"/DailyStoryInfo":                  538,
+	"/DatingInfo":                      361,
+	"/DispatchInfo":                    0,
+	"/EquipPresetInfo":                 253,
+	"/EvilCastleDailyRewardState":      441,
+	"/EvilCastleTowerInfo":             200,
+	"/FieldObjectInfo":                 28,
+	"/FieldTrapInfo":                   171,
+	"/FireWorksInfo":                   554,
+	"/FishingCollectionInfo":           465,
+	"/FishingTrapInfo":                 457,
+	"/FriendInfoList":                  204,
+	"/FriendshipInfo":                  612,
+	"/FriendshipSpecialEpisodeInfo":    623,
+	"/GuildInitInfo":                   332,
+	"/IdCardPresetInfo":                450,
+	"/LifeUserInfo":                    594,
+	"/MasterTitleInfo":                 590,
+	"/MiniEventHubInfo":                534,
+	"/MyLikeInfo":                      218,
+	"/MyRoomItemInfo":                  232,
+	"/PersonalInfo":                    199,
+	"/PrestigeSkinInfo":                425,
+	"/QuestMaxClearInfo":               137,
+	"/SpineInteractionAchievementInfo": 532,
+	"/TotalWarRewardState":             252,
+	"/TutorialInfo":                    101,
+}
+
+// Handle recognizes only audited, stateless empty-response endpoints. The
+// request must be a structurally valid protobuf with its normal nonzero
+// request sequence in field 1. Unknown paths return ok=false and no response.
+// proto is nil on success: protobuf's canonical empty-message encoding is zero
+// bytes.
+func Handle(path string, request []byte) (packetCode int, proto []byte, ok bool, err error) {
+	packetCode, ok = emptyResponses[path]
+	if !ok {
+		packetCode, proto, ok = initialResponse(path)
+	}
+	if !ok {
+		packetCode, ok = standaloneDefaults[path]
+	}
+	if !ok {
+		packetCode, ok = commandSuccess[path]
+		if !ok {
+			return 0, nil, false, nil
+		}
+	}
+	sequence, present, walkErr := wire.Varint(request, 1)
+	if walkErr != nil || !present || sequence == 0 {
+		if walkErr != nil {
+			return 0, nil, true, fmt.Errorf("%w: %s: %v", ErrInvalidRequest, path, walkErr)
+		}
+		return 0, nil, true, fmt.Errorf("%w: %s has no request sequence", ErrInvalidRequest, path)
+	}
+	return packetCode, proto, true, nil
+}
+
+// Service adapts this registry to session.Handler without importing session.
+type Service struct{}
+
+func (Service) Handle(path string, request []byte) (int, []byte, bool, error) {
+	return Handle(path, request)
+}
+
+// EmptyPacketCodes returns a detached copy for diagnostics and protocol tests.
+func EmptyPacketCodes() map[string]int {
+	result := make(map[string]int, len(emptyResponses))
+	for path, code := range emptyResponses {
+		result[path] = code
+	}
+	return result
+}