defmodule Mobius.MetricsTable.Monitor do
  @moduledoc false

  # module to save the metrics table to disk when shutting down Mobius

  use GenServer

  alias Mobius.MetricsTable

  @spec start_link([Mobius.arg()]) :: GenServer.on_start()
  def start_link(args) do
    GenServer.start_link(__MODULE__, args)
  end

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

    state =
      args
      |> Keyword.take([:name, :persistence_dir])
      |> Enum.into(%{})

    {:ok, state}
  end

  @impl GenServer
  def terminate(_reason, state) do
    MetricsTable.save(state.name, state.persistence_dir)
  end
end