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

  alias __MODULE__

  def ofp_type, do: 18

  def new(flows \\ []) do
    %Reply{flows: flows}
  end

  def read(<<flows_bin::bytes>>) do
    flows = Openflow.Multipart.FlowStats.read(flows_bin)
    %Reply{flows: flows}
  end

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

defmodule Openflow.Multipart.FlowStats do
  defstruct(
    table_id:      0,
    duration_sec:  0,
    duration_nsec: 0,
    priority:      0,
    idle_timeout:  0,
    hard_timeout:  0,
    flags:         0,
    cookie:        0,
    packet_count:  0,
    byte_count:    0,
    match:        [],
    instructions: []
  )

  alias __MODULE__

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

  # private functions

  defp do_read(acc, ""), do: Enum.reverse(acc)
  defp do_read(acc, <<length::16, _tail::bytes>> = binary) do
    <<flow_stats_bin::size(length)-bytes, rest::bytes>> = binary
    do_read([codec(flow_stats_bin)|acc], rest)
  end

  defp codec(<<_length::16, table_id_int::8, 0::8, duration_sec::32,
               duration_nsec::32, priority::16, idle::16, hard::16,
               flags_int::16, _::size(4)-unit(8), cookie::64,
               packet_count::64, byte_count::64, tail::bytes>>) do
    {match, instructions_bin} = Openflow.Match.read(tail)
    table_id = Openflow.Utils.get_enum(table_id_int, :table_id)
    flags = Openflow.Enums.int_to_flags(flags_int, :flow_mod_flags)
    instructions = Openflow.Instruction.read(instructions_bin)
    %FlowStats{table_id: table_id,
               duration_sec: duration_sec,
               duration_nsec: duration_nsec,
               priority: priority,
               idle_timeout: idle,
               hard_timeout: hard,
               flags: flags,
               cookie: cookie,
               packet_count: packet_count,
               byte_count: byte_count,
               match: match,
               instructions: instructions}
  end
end