defmodule Dtds do
  @moduledoc """
    This module provides a distributed topic discovery service.
    Producers and consumers of topics register themselves with the service
    and can query this information.
  """
  use Application

  @doc false
  def start(_type, _args) do
    Dtds.Supervisor.start_link()
  end

  @doc """
    Register a consumer for the topic. `term` can be a pid or a registered name.
  """
  def register_consumer(topic, term) do
    Dtds.TopicRegistry.register(Dtds.TopicRegistry, :consumer, topic, term)
  end

  @doc """
    Register a producer for the topic. `term` can be a pid or a registered name.
  """
  def register_producer(topic, term) do
    Dtds.TopicRegistry.register(Dtds.TopicRegistry, :producer, topic, term)
  end

  @doc """
    Un-register the topic from the consumers.
  """
  def unregister_consumer(topic) do
    Dtds.TopicRegistry.unregister(Dtds.TopicRegistry, :consumer, topic)
  end

  @doc """
    Un-register the topic from the producers.
  """
  def unregister_producer(topic) do
    Dtds.TopicRegistry.unregister(Dtds.TopicRegistry, :producer, topic)
  end

  @doc """
    Gets the registered name or pid of producer from the node: `node_id` for the `topic`
  """
  def get_producer_for_topic(node_id, topic) do
    GenServer.call({Dtds.TopicRegistry, node_id}, {:get, :producer, topic})
  end

  @doc """
    Gets the registered name or pid of consumer from the node: `node_id` for the `topic`
  """
  def get_consumer_for_topic(node_id, topic) do
    GenServer.call({Dtds.TopicRegistry, node_id}, {:get, :consumer, topic})
  end

  @doc """
    Gets the list of nodes who have the consumers for `topic`
  """
  def get_consumer_nodes(topic) do
    Dtds.TopicDiscovery.get_consumers_for_topic(Dtds.TopicDiscovery, topic)
  end

  @doc """
    Gets the list of nodes who have the producers for `topic`
  """
  def get_producer_nodes(topic) do
    Dtds.TopicDiscovery.get_producers_for_topic(Dtds.TopicDiscovery, topic)
  end
end