클라이언트 대시보드 통계 실지표 연동 및 백엔드 API 구현

backend/internal/repository/clickhouse_repo.go

@@ -195,3 +195,44 @@ func (r *ClickHouseRepository) Ping(ctx context.Context) error {
 	}
 	return r.conn.Ping(ctx)
 }
+
+func (r *ClickHouseRepository) CountFailuresSince(ctx context.Context, since time.Time, tenantID string) (int64, error) {
+	query := `
+		SELECT count()
+		FROM audit_logs
+		WHERE status = 'failure' AND timestamp >= ?
+	`
+	args := []any{since}
+	if tenantID != "" {
+		query += " AND JSONExtractString(details, 'tenant_id') = ?"
+		args = append(args, tenantID)
+	}
+
+	var count int64
+	err := r.conn.QueryRow(ctx, query, args...).Scan(&count)
+	if err != nil {
+		return 0, fmt.Errorf("failed to count failures: %w", err)
+	}
+	return count, nil
+}
+
+func (r *ClickHouseRepository) CountActiveSessionsSince(ctx context.Context, since time.Time, tenantID string) (int64, error) {
+	// We use uniqExact(session_id) to count unique sessions that had success events recently.
+	query := `
+		SELECT uniqExact(session_id)
+		FROM audit_logs
+		WHERE status = 'success' AND timestamp >= ? AND session_id != ''
+	`
+	args := []any{since}
+	if tenantID != "" {
+		query += " AND JSONExtractString(details, 'tenant_id') = ?"
+		args = append(args, tenantID)
+	}
+
+	var count int64
+	err := r.conn.QueryRow(ctx, query, args...).Scan(&count)
+	if err != nil {
+		return 0, fmt.Errorf("failed to count active sessions: %w", err)
+	}
+	return count, nil
+}