defmodule Openflow.Action.NxConntrack do
  import Bitwise

  defstruct(
    flags:       [],
    zone_src:     nil,
    zone_imm:     0,
    zone_offset:  nil,
    zone_n_bits:  nil,
    recirc_table: 255,
    alg:          0,
    exec:         []
  )

  @experimenter 0x00002320
  @nxast 35

  alias __MODULE__

  def new(options \\ []) do
    %NxConntrack{flags:        options[:flags] || [],
                 zone_src:     options[:zone_src],
                 zone_imm:     options[:zone_imm] || 0,
                 zone_offset:  options[:zone_offset],
                 zone_n_bits:  options[:zone_n_bits],
                 recirc_table: options[:recirc_table] || 255,
                 alg:          options[:alg]  || 0,
                 exec:         options[:exec] || []}
  end

  def to_binary(%NxConntrack{
        flags:        flags,
        zone_src:     zone_src,
        zone_offset:  zone_ofs,
        zone_n_bits:  zone_n_bits,
        zone_imm:     zone_imm,
        recirc_table: recirc_table,
        alg:          alg,
        exec:         exec}) do
    flags_int = Openflow.Enums.flags_to_int(flags, :nx_conntrack_flags)
    {src_bin, ofs_nbits} = if not (is_nil(zone_src)) do
      zone_src_bin = Openflow.Match.codec_header(zone_src)
      {zone_src_bin, (zone_ofs <<< 6) ||| (zone_n_bits - 1)}
    else
      {<<0::32>>, zone_imm}
    end
    exec_bin = Openflow.Action.to_binary(exec)
    exp_body = <<@experimenter::32, @nxast::16, flags_int::16,
                 src_bin::bytes, ofs_nbits::16, recirc_table::8,
                 0::size(3)-unit(8), alg::16, exec_bin::bytes>>
    exp_body_size =  byte_size(exp_body)
    padding_length = Openflow.Utils.padding(4 + exp_body_size, 8)
    length = 4 + exp_body_size + padding_length
    <<0xffff::16, length::16, exp_body::bytes, 0::size(padding_length)-unit(8)>>
  end

  def read(<<@experimenter::32, @nxast::16, flags_int::16,
             src_bin::4-bytes, ofs_nbits::16-bits, recirc_table::8,
             _::size(3)-unit(8), alg::16, exec_bin::bytes>>) do
    flags = Openflow.Enums.int_to_flags(flags_int, :nx_conntrack_flags)
    exec = Openflow.Action.read(exec_bin)
    ct = %NxConntrack{
      flags:        flags,
      recirc_table: recirc_table,
      alg:          alg,
      exec:         exec
    }
    case src_bin do
      <<0::32>> ->
        <<zone_imm::16>> = ofs_nbits
        %{ct|zone_imm: zone_imm}
      binary when is_binary(binary) ->
        zone_src = Openflow.Match.codec_header(binary)
        <<ofs::10, n_bits::6>> = ofs_nbits
        %{ct|zone_src: zone_src, zone_offset: ofs, zone_n_bits: n_bits + 1}
    end
  end
end