crdtSyncWebSocketHandler function

A Dart Frog Handler that upgrades the request and hands the socket to host, the CRDT-aware (DocumentSessionHost) side of the protocol.

// routes/sync.dart
Future<Response> onRequest(RequestContext context) async {
  return crdtSyncWebSocketHandler(context.read<DocumentSessionHost>())(
    context,
  );
}

Calling this completes the WebSocket upgrade. From then on the response is a 101, so a client the host will not take — stopped, disposed, or a session id already in use — is hung up on, with no status code and no reason. Refuse before the call to answer with one:

Future<Response> onRequest(RequestContext context) async {
  final token = context.request.headers[HttpHeaders.authorizationHeader];
  if (!await isAuthorized(token)) {
    return Response(statusCode: HttpStatus.unauthorized);
  }
  return crdtSyncWebSocketHandler(context.read<DocumentSessionHost>())(
    context,
  );
}

The same window is where SessionHostServer.isRunning belongs, for a shutdown that should answer 503 rather than accept a socket and close it.

The document id travels inside the protocol's own frames, not in the URL, so no route parameter is needed. A routes/sync/[documentId].dart route still works and is the place to authorize per document.

protocols, allowedOrigins and pingInterval are passed straight to dart_frog_web_socket. allowedOrigins is the one to set for a browser client: unset, any origin may connect.

pingInterval is a WebSocket-level ping, which is not the protocol's own ping (Protocol.pingInterval, 15s, answered with a pong and carrying the client's version vector). They serve different purposes — setting one does not let you drop the other.