renderSSEString method

Future<String> renderSSEString(Stream<String> stream, { ContentType? contentType, int status = HttpStatus.ok, Map<String, String>? headers, })

Render SSE (Server-Sent Events) stream to the client. This method sets up the necessary headers for SSE and streams data to the client. The stream function should return a stream of strings to be sent as SSE messages. Each message is formatted according to the SSE protocol. The connection is kept alive until the stream is closed. Returns a Future<String> that completes when the stream is closed.

Implementation

Future<String> renderSSEString(
  Stream<String> stream, {
  ContentType? contentType,
  int status = HttpStatus.ok,
  Map<String, String>? headers,
}) async {
  contentType ??= ContentType('text', 'event-stream', charset: 'utf-8');

  headers ??= {
    'Cache-Control': 'no-cache',
    'Connection': 'keep-alive',
    'X-Accel-Buffering': 'no', // For Nginx
  };

  headers.forEach((key, value) {
    response.headers.set(key, value);
  });

  response.statusCode = status;
  response.headers.contentType = contentType;
  response.bufferOutput = false;

  await for (var sse in stream) {
    response.write(sse.toString());
    await response.flush();
  }

  await response.close();
  return ""; // Return empty string for SSE completion
}