How can I create a synced countdown with rails and actioncable?

Question

I'm building an app where on a specific page there needs to be a countdown synced for all the connected clients. The countdown will start, pause and reset based on certain user inputs.

I started toying around with the idea of using ActionCable PeriodicTimer. Before fully committing with that, however, I wanted to explore the potential of building this with built-in hotwire features such as streams and broadcasts.

I started to look into concurrent-ruby and its TimerTask. It kind of works, however, it can be quite messy to maintain and debug.

Do you have any pointers?