if Code.ensure_loaded?(Phoenix.PubSub) do
  defmodule Dust.PubSubBridge do
    @moduledoc """
    Bridges Dust events to Phoenix.PubSub.

    When configured with a `:pubsub` option, registers a catch-all `**` callback
    on each store that broadcasts every event to the PubSub topic `"dust:{store}"`.

    Subscribers subscribe to the store topic and filter in `handle_info`:

        Phoenix.PubSub.subscribe(MyApp.PubSub, "dust:james/blog")

        def handle_info({:dust_event, event}, state) do
          # event is a map with :store, :path, :op, :value, etc.
        end
    """

    @doc "Register PubSub broadcasting for all configured stores."
    def register(pubsub, stores) do
      Enum.each(stores, fn store ->
        Dust.SyncEngine.on(store, "**", fn event ->
          Phoenix.PubSub.broadcast(pubsub, "dust:#{store}", {:dust_event, event})
        end)
      end)
    end
  end
end