I want to add some content at the end of first children. Below is the code sample.

  String content=  '''GetPage(
      name: Routes.user,
      page: () => UserScreen(),
      binding: UserBindings(),
      middlewares: [ConnectivityMiddleware(), AuthMiddleware()],
      transition: Transition.fadeIn,
      children: [
        GetPage(
          name: Routes.userDetails,
          page: () => UserDetailsScreen(),
          binding: UserDetailsBindings(),
          middlewares: [ConnectivityMiddleware(), AuthMiddleware()],
          transition: Transition.fadeIn,
          children: [
            GetPage(
                name: Routes.userAddress,
                page: () => UserAddressScreen(),
                binding: UserAddressBindings(),
                middlewares: [ConnectivityMiddleware(), AuthMiddleware()],
                transition: Transition.fadeIn),
          ],
        ),
     
      ],
    )''';

Content to add are below.

String contentToAdd = '''GetPage(
                name: Routes.userRole,
                page: () => UserRoleScreen(),
                binding: UserRoleBindings(),
                middlewares: [ConnectivityMiddleware(), AuthMiddleware()],
                transition: Transition.fadeIn)''';

Desire output:-

String output =  '''GetPage(
      name: Routes.user,
      page: () => UserScreen(),
      binding: UserBindings(),
      middlewares: [ConnectivityMiddleware(), AuthMiddleware()],
      transition: Transition.fadeIn,
      children: [
        GetPage(
          name: Routes.userDetails,
          page: () => UserDetailsScreen(),
          binding: UserDetailsBindings(),
          middlewares: [ConnectivityMiddleware(), AuthMiddleware()],
          transition: Transition.fadeIn,
          children: [
            GetPage(
                name: Routes.userAddress,
                page: () => UserAddressScreen(),
                binding: UserAddressBindings(),
                middlewares: [ConnectivityMiddleware(), AuthMiddleware()],
                transition: Transition.fadeIn),
          ],
        ),
         GetPage(
                name: Routes.userRole,
                page: () => UserRoleScreen(),
                binding: UserRoleBindings(),
                middlewares: [ConnectivityMiddleware(), AuthMiddleware()],
                transition: Transition.fadeIn),
      ],
    )''';

What I have tried is below. But it is only working when there is only one children. If more than one children is coming like above, code is not working.

  if (content.contains('children: [')) {
    final pattern = RegExp(r'(s*children:s*[.*?)(s*]s*))', dotAll: true);
    final updatedContent = content.replaceAllMapped(
      pattern,
      (match) {
        final childrenPart = match.group(1)!;
        final closingPart = match.group(2)!;
        return '$childrenPartn$contentToAdd$closingPart';
      },
    );
  }

Please help me to resolve this issue. Child can be nested n number of time but I have to always add to first children only.