defmodule Podbox.PubSub do
  @moduledoc """
  A wrapper around a registry for PubSub.
  """

  @doc false
  @spec child_spec(any) :: Supervisor.child_spec()
  def child_spec(_) do
    Registry.child_spec(
      keys: :duplicate,
      name: __MODULE__,
      partitions: System.schedulers_online()
    )
  end

  @doc "Subscribe to a topic"
  @spec subscribe(String.t(), Keyword.t()) :: :ok | {:error, any}
  def subscribe(topic, _opts \\ []) do
    with {:ok, _} <- Registry.register(__MODULE__, topic, nil) do
      :ok
    end
  end

  @doc "Unsubscribe from a topic"
  @spec unsubscribe(String.t()) :: :ok | {:error, any}
  def unsubscribe(topic) do
    Registry.unregister(__MODULE__, topic)
  end

  @doc "Broadcast a message to a topic"
  @spec broadcast(String.t(), any, any) :: :ok | {:error, any}
  def broadcast(topic, _event \\ nil, message) do
    Registry.dispatch(__MODULE__, topic, fn entries ->
      for {pid, _} <- entries, do: send(pid, {topic, message})
    end)
  end
end