border_guard

defmodule BorderGuard do
  @moduledoc """
  Documentation for `BorderGuard`.
  """
  use GenServer

  @default_opts [
    latency: 0,
    response: :ok,
    request_error_response: :error,
    force_error: false
  ]

  def init(opts) do
    {:ok, opts}
  end

  def start_link(opts \\ []) do
    GenServer.start_link(__MODULE__, get_defaults(opts))
  end

  defmacro handle(name, request_opts \\ [], do: request) do
    if Application.get_env(:border_guard, :enabled) do
      # Fetch or spawn handler process for module
      BorderGuard.Supervisor
      |> DynamicSupervisor.start_child({BorderGuard.Handler, get_handler_opts(name)})
      |> return_pid()
      |> GenServer.call(request_opts, :infinity)
    else
      quote do
        # TODO: Add logging
        # {time_in_microseconds, ret_val} = :timer.tc(fn -> unquote(request) end)
        # IO.inspect(time_in_microseconds, label: "time_in_microseconds")
        # ret_val
        unquote(request)
      end
    end
  end

  defp get_defaults(opts) do
    @default_opts
    |> Keyword.merge(Application.get_env(:border_guard, :defaults, []))
    |> Keyword.merge(opts)
  end

  defp get_handler_opts(name) do
    Application.get_env(:border_guard, name, [])
    |> get_defaults()
    |> Keyword.merge(name: name)
  end

  defp return_pid({:ok, pid}), do: pid
  defp return_pid({:error, {:already_started, pid}}), do: pid
end