defmodule Membrane.RTP.PayloaderBin do
  @moduledoc """
  Module responsible for payloading a stream to RTP format and preparing RTP headers.
  """

  use Membrane.Bin

  alias Membrane.ParentSpec

  def_input_pad :input, demand_unit: :buffers, caps: :any

  def_output_pad :output, caps: :any, demand_unit: :buffers

  def_options payloader: [
                spec: module(),
                description: "Payloader module used for payloading a stream to RTP format"
              ],
              ssrc: [spec: RTP.ssrc_t()],
              payload_type: [spec: RTP.payload_type_t()],
              clock_rate: [spec: RTP.clock_rate_t()],
              alignment: [
                default: 1,
                spec: pos_integer(),
                description: """
                Number of bytes that each packet should be aligned to.
                Alignment is achieved by adding RTP padding.
                """
              ]

  @impl true
  def handle_init(opts) do
    links = [
      link_bin_input()
      |> to(:payloader, opts.payloader)
      |> to(:serializer, %Membrane.RTP.Serializer{
        ssrc: opts.ssrc,
        payload_type: opts.payload_type,
        clock_rate: opts.clock_rate,
        alignment: opts.alignment
      })
      |> to_bin_output()
    ]

    {{:ok, spec: %ParentSpec{links: links}}, %{}}
  end
end