add admin user last used support

backend/internal/service/admin_service.go

@@ -557,6 +557,20 @@ func (s *adminServiceImpl) ListUsers(ctx context.Context, page, pageSize int, fi
 	if err != nil {
 		return nil, 0, err
 	}
+	if len(users) > 0 {
+		userIDs := make([]int64, 0, len(users))
+		for i := range users {
+			userIDs = append(userIDs, users[i].ID)
+		}
+		lastUsedByUserID, latestErr := s.userRepo.GetLatestUsedAtByUserIDs(ctx, userIDs)
+		if latestErr != nil {
+			logger.LegacyPrintf("service.admin", "failed to load user last_used_at in batch: err=%v", latestErr)
+		} else {
+			for i := range users {
+				users[i].LastUsedAt = lastUsedByUserID[users[i].ID]
+			}
+		}
+	}
 	// 批量加载用户专属分组倍率
 	if s.userGroupRateRepo != nil && len(users) > 0 {
 		if batchRepo, ok := s.userGroupRateRepo.(userGroupRateBatchReader); ok {
@@ -601,6 +615,12 @@ func (s *adminServiceImpl) GetUser(ctx context.Context, id int64) (*User, error)
 	if err != nil {
 		return nil, err
 	}
+	lastUsedAt, latestErr := s.userRepo.GetLatestUsedAtByUserID(ctx, id)
+	if latestErr != nil {
+		logger.LegacyPrintf("service.admin", "failed to load user last_used_at: user_id=%d err=%v", id, latestErr)
+	} else {
+		user.LastUsedAt = lastUsedAt
+	}
 	// 加载用户专属分组倍率
 	if s.userGroupRateRepo != nil {
 		rates, err := s.userGroupRateRepo.GetByUserID(ctx, id)

backend/internal/service/admin_service_list_users_test.go

@@ -6,6 +6,7 @@ import (
 	"context"
 	"errors"
 	"testing"
+	"time"
 
 	"github.com/Wei-Shaw/sub2api/internal/pkg/pagination"
 	"github.com/stretchr/testify/require"
@@ -16,6 +17,8 @@ type userRepoStubForListUsers struct {
 	users                 []User
 	err                   error
 	listWithFiltersParams pagination.PaginationParams
+	lastUsedByUserID      map[int64]*time.Time
+	lastUsedErr           error
 }
 
 func (s *userRepoStubForListUsers) ListWithFilters(_ context.Context, params pagination.PaginationParams, _ UserListFilters) ([]User, *pagination.PaginationResult, error) {
@@ -32,6 +35,26 @@ func (s *userRepoStubForListUsers) ListWithFilters(_ context.Context, params pag
 	}, nil
 }
 
+func (s *userRepoStubForListUsers) GetLatestUsedAtByUserIDs(_ context.Context, userIDs []int64) (map[int64]*time.Time, error) {
+	if s.lastUsedErr != nil {
+		return nil, s.lastUsedErr
+	}
+	result := make(map[int64]*time.Time, len(userIDs))
+	for _, userID := range userIDs {
+		if ts, ok := s.lastUsedByUserID[userID]; ok {
+			result[userID] = ts
+		}
+	}
+	return result, nil
+}
+
+func (s *userRepoStubForListUsers) GetLatestUsedAtByUserID(_ context.Context, userID int64) (*time.Time, error) {
+	if s.lastUsedErr != nil {
+		return nil, s.lastUsedErr
+	}
+	return s.lastUsedByUserID[userID], nil
+}
+
 type userGroupRateRepoStubForListUsers struct {
 	batchCalls int
 	singleCall []int64
@@ -130,3 +153,21 @@ func TestAdminService_ListUsers_PassesSortParams(t *testing.T) {
 		SortOrder: "ASC",
 	}, userRepo.listWithFiltersParams)
 }
+
+func TestAdminService_ListUsers_PopulatesLastUsedAt(t *testing.T) {
+	lastUsed := time.Now().UTC().Add(-30 * time.Minute).Truncate(time.Second)
+	userRepo := &userRepoStubForListUsers{
+		users: []User{{ID: 101, Email: "u@example.com"}},
+		lastUsedByUserID: map[int64]*time.Time{
+			101: &lastUsed,
+		},
+	}
+	svc := &adminServiceImpl{userRepo: userRepo}
+
+	users, total, err := svc.ListUsers(context.Background(), 1, 20, UserListFilters{}, "", "")
+	require.NoError(t, err)
+	require.Equal(t, int64(1), total)
+	require.Len(t, users, 1)
+	require.NotNil(t, users[0].LastUsedAt)
+	require.WithinDuration(t, lastUsed, *users[0].LastUsedAt, time.Second)
+}

backend/internal/service/user.go

@@ -26,6 +26,7 @@ type User struct {
 	SignupSource   string
 	LastLoginAt    *time.Time
 	LastActiveAt   *time.Time
+	LastUsedAt     *time.Time
 	CreatedAt      time.Time
 	UpdatedAt      time.Time