Method writeMessage

packages/core/router/sse-stream.ts:147–161

* Calls `.write` but handles the drain if needed

(
    message: MessageEvent,
    cb: (error: Error | null | undefined) => void,
  )

   * Calls `.write` but handles the drain if needed
   */
  writeMessage(
    message: MessageEvent,
    cb: (error: Error | null | undefined) => void,
  ) {
    if (message.id === undefined || message.id === null) {
      this.lastEventId!++;
      message.id = this.lastEventId!.toString();
    }

    if (!this.write(message, 'utf-8')) {
      this.once('drain', cb);
    } else {
      process.nextTick(cb);
    }
  }
}