defmodule Localiser.Web.Channels.RoomChannel do
  use Phoenix.Channel

  @impl true
  def join("rooms:occupancy", _params, socket) do
    Phoenix.PubSub.subscribe(Localiser.PubSub, "rooms:occupancy")
    {:ok, socket}
  end

  @impl true
  def handle_info({:room_occupancy_changed, room_id, occupants}, socket) do
    push(socket, "occupancy_changed", %{
      room_id:   room_id,
      occupants: MapSet.to_list(occupants)
    })
    {:noreply, socket}
  end

  def handle_info(_msg, socket), do: {:noreply, socket}
end