feat: backend service

backend/internal/lobby/cascade.go

@@ -0,0 +1,81 @@
+package lobby
+
+import (
+	"context"
+	"errors"
+	"fmt"
+
+	"github.com/google/uuid"
+	"go.uber.org/zap"
+)
+
+// OnUserBlocked releases every lobby binding owned by the user under
+// the `blocked` semantics: active memberships flip to `blocked`,
+// pending applications get rejected, pending invites incoming get
+// declined / outgoing get revoked, race-name entries are deleted, and
+// owned games in non-running statuses are cancelled.
+//
+// Implements `internal/user.LobbyCascade.OnUserBlocked`. Errors during
+// the cascade are joined and returned but never roll back the
+// already-committed user write — the canonical state is the row in
+// Postgres.
+func (s *Service) OnUserBlocked(ctx context.Context, userID uuid.UUID) error {
+	return s.runCascade(ctx, userID, MembershipStatusBlocked)
+}
+
+// OnUserDeleted runs the same cascade as OnUserBlocked but transitions
+// memberships to `removed` instead of `blocked`. Implements
+// `internal/user.LobbyCascade.OnUserDeleted`.
+func (s *Service) OnUserDeleted(ctx context.Context, userID uuid.UUID) error {
+	return s.runCascade(ctx, userID, MembershipStatusRemoved)
+}
+
+func (s *Service) runCascade(ctx context.Context, userID uuid.UUID, membershipStatus string) error {
+	snap, err := s.deps.Store.LoadCascadeSnapshot(ctx, userID)
+	if err != nil {
+		return fmt.Errorf("lobby cascade: load snapshot: %w", err)
+	}
+	if snap.empty() {
+		return nil
+	}
+	now := s.deps.Now().UTC()
+	if err := s.deps.Store.CascadeUser(ctx, userID, snap, membershipStatus, now); err != nil {
+		return fmt.Errorf("lobby cascade: write: %w", err)
+	}
+	s.deps.Cache.EvictUserMemberships(userID)
+	s.deps.Cache.EvictUserRaceNames(userID)
+	s.deps.Cache.EvictOwnerGames(userID)
+
+	var notifyErrs []error
+	for _, gameID := range snap.OwnedGameIDs {
+		s.deps.Cache.RemoveGame(gameID)
+	}
+	if len(snap.ActiveMembershipIDs) > 0 {
+		intent := LobbyNotification{
+			Kind:           NotificationLobbyMembershipRemoved,
+			IdempotencyKey: "user-cascade-membership:" + userID.String(),
+			Recipients:     []uuid.UUID{userID},
+			Payload: map[string]any{
+				"reason": membershipStatus,
+			},
+		}
+		if pubErr := s.deps.Notification.PublishLobbyEvent(ctx, intent); pubErr != nil {
+			notifyErrs = append(notifyErrs, pubErr)
+		}
+	}
+	if len(notifyErrs) > 0 {
+		s.deps.Logger.Warn("lobby cascade notification failures",
+			zap.String("user_id", userID.String()),
+			zap.Int("notify_errors", len(notifyErrs)))
+	}
+	return errors.Join(notifyErrs...)
+}
+
+func (snap CascadeUserSnapshot) empty() bool {
+	return len(snap.OwnedGameIDs) == 0 &&
+		len(snap.ActiveMembershipIDs) == 0 &&
+		len(snap.PendingApplications) == 0 &&
+		len(snap.IncomingInvites) == 0 &&
+		len(snap.OutgoingInvites) == 0 &&
+		len(snap.RaceNameKeys) == 0
+}