qmi

defmodule QMI.Codec.WirelessData do
  @moduledoc """
  Codec for making wireless data service requests
  """

  @start_network_interface 0x0020

  @typedoc """
  Options for whens starting a network interface

  * `:apn` - the name of our APN
  """
  @type start_network_interface_opt() :: {:apn, String.t()}

  @typedoc """
  Report from starting the network interface
  """
  @type start_network_report() :: %{packet_data_handle: non_neg_integer()}

  @doc """
  Send command to request the that the network interface starts to receive data
  """
  @spec start_network_interface([start_network_interface_opt()]) :: QMI.request()
  def start_network_interface(opts \\ []) do
    {tlvs, size} = make_tlvs(opts, [], 0)
    payload = [<<@start_network_interface::little-16, size::little-16>>, tlvs]

    %{service_id: 0x01, payload: payload, decode: &parse_start_network_interface_resp/1}
  end

  defp make_tlvs([], tlvs, size) do
    {tlvs, size}
  end

  defp make_tlvs([{:apn, apn} | rest], tlvs, size) do
    apn_size = byte_size(apn)
    new_size = size + 3 + apn_size
    new_tlvs = [tlvs, <<0x14, apn_size::little-16>>, apn]
    make_tlvs(rest, new_tlvs, new_size)
  end

  defp parse_start_network_interface_resp(
         <<@start_network_interface::little-16, size::little-16, tlvs::size(size)-binary>>
       ) do
    {:ok, parse_start_network_interface_tlvs(%{}, tlvs)}
  end

  defp parse_start_network_interface_resp(_other) do
    {:error, :unexpected_response}
  end

  defp parse_start_network_interface_tlvs(parsed, <<>>) do
    parsed
  end

  defp parse_start_network_interface_tlvs(
         parsed,
         <<0x01, 0x04, 0x00, packet_data_handle::little-32, rest::binary>>
       ) do
    parsed
    |> Map.put(:packet_data_handle, packet_data_handle)
    |> parse_start_network_interface_tlvs(rest)
  end

  defp parse_start_network_interface_tlvs(
         parsed,
         <<_type, length::little-16, _values::size(length)-unit(8)-binary, rest::binary>>
       ) do
    parse_start_network_interface_tlvs(parsed, rest)
  end
end