defmodule Openflow.Multipart.Queue.Reply do
  defstruct(
    version: 4,
    xid: 0,
    # virtual field
    datapath_id: nil,
    aux_id: nil,
    flags: [],
    queues: []
  )

  alias __MODULE__

  def ofp_type, do: 18

  def read(<<queues_bin::bytes>>) do
    queues = Openflow.Multipart.QueueStats.read(queues_bin)
    %Reply{queues: queues}
  end

  def append_body(%Reply{queues: queues} = message, %Reply{flags: [:more], queues: continue}) do
    %{message | queues: [continue | queues]}
  end

  def append_body(%Reply{queues: queues} = message, %Reply{flags: [], queues: continue}) do
    new_queues =
      [continue | queues]
      |> Enum.reverse()
      |> List.flatten()

    %{message | queues: new_queues}
  end
end

defmodule Openflow.Multipart.QueueStats do
  defstruct(
    port_number: 0,
    queue_id: 0,
    tx_bytes: 0,
    tx_packets: 0,
    tx_errors: 0,
    duration_sec: 0,
    duration_nsec: 0
  )

  alias __MODULE__

  def read(binary) do
    do_read([], binary)
  end

  # private functions

  defp do_read(acc, ""), do: Enum.reverse(acc)

  defp do_read(acc, <<queue_bin::40-bytes, rest::bytes>>) do
    do_read([codec(queue_bin) | acc], rest)
  end

  defp codec(
         <<port_no::32, queue_id::32, tx_bytes::64, tx_packets::64, tx_errors::64,
           duration_sec::32, duration_nsec::32>>
       ) do
    %QueueStats{
      port_number: port_no,
      queue_id: queue_id,
      tx_bytes: tx_bytes,
      tx_packets: tx_packets,
      tx_errors: tx_errors,
      duration_sec: duration_sec,
      duration_nsec: duration_nsec
    }
  end
end