defmodule Prymn.Messaging.Connection do
  use GenServer

  require Logger

  @dialyzer {:nowarn_function, init: 1}

  def start_link(%{name: name} = init_arg) do
    GenServer.start_link(__MODULE__, init_arg, name: name)
  end

  def publish(server, subject, payload) do
    GenServer.call(server, {:pub, subject, payload})
  end

  def subscribe(server, subject, reply) do
    GenServer.call(server, {:sub, subject, reply})
  end

  @impl true
  def init(_init_arg) do
    Process.flag(:trap_exit, true)

    connect_opts = %{
      host: "localhost",
      username: "prymn_admin",
      password: "prymn_admin",
      auth_required: true
    }

    case Gnat.start_link(connect_opts) do
      {:ok, pid} ->
        {:ok, pid}

      {:error, reason} ->
        # Let the supervisor restart the Connection after a short delay
        Logger.info("Initial NATS connection failed. Restarting...")
        Process.sleep(1000)
        {:stop, reason}
    end
  end

  @impl true
  def handle_call({:pub, subject, payload}, _from, conn_pid) do
    :ok = Gnat.pub(conn_pid, subject, payload)

    {:reply, :ok, conn_pid}
  end

  def handle_call({:sub, subject, reply}, _from, conn_pid) do
    {:ok, cons_pid} = GenServer.start_link(Prymn.Messaging.FooConsumer, reply)
    {:ok, sub} = Gnat.sub(conn_pid, cons_pid, subject)

    {:reply, {:ok, sub}, conn_pid}
  end

  @impl true
  def handle_info({:EXIT, pid, reason}, conn_pid) when conn_pid == pid do
    Logger.info("NATS connection lost (#{reason})")
    {:stop, {:shutdown, :connection_closed}, conn_pid}
  end
end