defmodule CA.TSP do
  @moduledoc "CA/TSP TCP server."
  require CA

  def code(), do: :binary.encode_hex(:crypto.strong_rand_bytes(8))

  def start_link(port: port), do: {:ok, :erlang.spawn_link(fn -> listen(port) end)}

  def child_spec(opt) do
    %{
      id: TSP,
      start: {CA.TSP, :start_link, [opt]},
      type: :supervisor,
      restart: :permanent,
      shutdown: 500
    }
  end

  def listen(port) do
    {:ok, socket} =
      :gen_tcp.listen(
        port,
        [:binary, {:packet, 0}, {:active, false}, {:reuseaddr, true}]
      )

    accept(socket)
  end

  def accept(socket) do
    {:ok, fd} = :gen_tcp.accept(socket)
    :erlang.spawn(fn -> __MODULE__.loop(fd) end)
    accept(socket)
  end

  def message(_socket, cms) do
    :logger.info(~c"Unknown message request ~p", [cms])
  end

  def answer(socket, res) do
    :gen_tcp.send(socket, res)
  end

  def loop(socket) do
    case :gen_tcp.recv(socket, 0) do
      {:ok, data} ->
        {:ok, dec} = :KEP.decode(:TimeStampReq, data)
        :io.format(~c"TimeStampReq:~n~p~n", [dec])
        __MODULE__.message(socket, dec)
        __MODULE__.loop(socket)

      {:error, _} ->
        :exit
    end
  end
end