defmodule Membrane.Protocol.SDP.Media do
  @moduledoc """
  This module represents Media field of SDP.

  For more details please see [RFC4566 Section 5.14](https://tools.ietf.org/html/rfc4566#section-5.14)
  """
  use Bunch
  @enforce_keys [:type, :ports, :protocol, :fmt]
  defstruct @enforce_keys ++
              [
                :title,
                :encryption,
                bandwidth: [],
                attributes: [],
                connection_data: []
              ]

  alias Membrane.Protocol.SDP.{Attribute, Bandwidth, ConnectionData, Encryption, Session}

  @typedoc """
  Represents type of media. In [RFC4566](https://tools.ietf.org/html/rfc4566#section-5.14)
  there are defined "audio", "video", "text", "application", and "message" types.

  Known types are represented as atoms others are binaries.
  """
  @type type :: :audio | :video | :text | :application | :message | binary()

  @type t :: %__MODULE__{
          type: type(),
          ports: [:inet.port_number()],
          protocol: binary(),
          fmt: binary() | [0..127],
          title: binary() | nil,
          connection_data: [ConnectionData.sdp_address()],
          bandwidth: [Bandwidth.t()],
          encryption: Encryption.t() | nil,
          attributes: [binary()]
        }

  @spec parse(binary()) :: {:ok, t()} | {:error, :invalid_media_spec | :malformed_port_number}
  def parse(media) do
    withl conn: [type, port, proto, fmt] <- String.split(media, " ", parts: 4),
          int: {port_no, port_options} when port_no in 0..65_535 <- Integer.parse(port),
          fmt: {:ok, fmt} <- parse_fmt(fmt, proto) do
      media = %__MODULE__{
        type: parse_type(type),
        ports: gen_ports(port_no, port_options),
        protocol: proto,
        fmt: fmt
      }

      {:ok, media}
    else
      conn: _ -> {:error, :invalid_media_spec}
      int: _ -> {:error, :malformed_port_number}
      fmt: error -> error
    end
  end

  @spec parse_optional([binary()], t()) :: {:ok, {[binary()], t()}} | {:error, atom()}
  def parse_optional(lines, media)

  def parse_optional([""], media), do: {:ok, {[""], finalize_optional_parsing(media)}}

  def parse_optional(["m=" <> _ | _] = lines, media),
    do: {:ok, {lines, finalize_optional_parsing(media)}}

  def parse_optional(["i=" <> title | rest], media),
    do: parse_optional(rest, %__MODULE__{media | title: title})

  def parse_optional(["c=" <> conn | rest], %__MODULE__{connection_data: info} = media) do
    with {:ok, conn} <- ConnectionData.parse(conn) do
      conn
      |> Bunch.listify()
      ~> %__MODULE__{media | connection_data: &1 ++ info}
      ~> parse_optional(rest, &1)
    end
  end

  def parse_optional(["b=" <> bandwidth | rest], %__MODULE__{bandwidth: acc_bandwidth} = media) do
    with {:ok, bandwidth} <- Bandwidth.parse(bandwidth) do
      bandwidth = %__MODULE__{media | bandwidth: [bandwidth | acc_bandwidth]}
      parse_optional(rest, bandwidth)
    end
  end

  def parse_optional(["k=" <> encryption | rest], media) do
    with {:ok, encryption} <- Encryption.parse(encryption) do
      encryption = %__MODULE__{media | encryption: encryption}
      parse_optional(rest, encryption)
    end
  end

  def parse_optional(["a=" <> attribute | rest], %__MODULE__{attributes: attrs} = media) do
    with {:ok, attribute} <- Attribute.parse(attribute),
         {:ok, attribute} <- Attribute.parse_media_attribute(attribute, media.type) do
      media = %__MODULE__{media | attributes: [attribute | attrs]}
      parse_optional(rest, media)
    end
  end

  @spec apply_session(__MODULE__.t(), Session.t()) :: __MODULE__.t()
  def apply_session(media, session) do
    session
    |> Map.from_struct()
    |> Enum.reduce(Map.from_struct(media), fn
      {inherited_key, value}, acc
      when inherited_key == :encryption ->
        if acc[inherited_key] != nil,
          do: acc,
          else: Map.put(acc, inherited_key, value)

      {inherited_key, value}, acc when inherited_key in [:connection_data, :bandwidth] ->
        if acc[inherited_key] != [],
          do: acc,
          else: Map.put(acc, inherited_key, value)

      _, acc ->
        acc
    end)
    ~> struct(__MODULE__, &1)
  end

  defp finalize_optional_parsing(%__MODULE__{attributes: attrs} = media) do
    %__MODULE__{media | attributes: Enum.reverse(attrs)}
  end

  defp parse_type(type) when type in ["audio", "video", "text", "application", "message"],
    do: String.to_atom(type)

  defp parse_type(type) when is_binary(type), do: type

  defp parse_fmt(fmt, proto) when proto == "RTP/AVP" or proto == "RTP/SAVP" do
    fmt
    |> String.split(" ")
    |> Bunch.Enum.try_map(fn single_fmt ->
      case Integer.parse(single_fmt) do
        {parsed_fmt, ""} -> {:ok, parsed_fmt}
        _ -> {:error, :invalid_fmt}
      end
    end)
  end

  defp parse_fmt(fmt, _), do: {:ok, fmt}

  defp gen_ports(port_no, "/" <> port_count) do
    port_count
    |> Integer.parse()
    |> case do
      {port_count, ""} ->
        port_no
        |> Stream.unfold(fn port_no -> {port_no, port_no + 2} end)
        |> Stream.take(port_count)
        |> Enum.into([])

      _ ->
        {:error, :invalid_port_count}
    end
  end

  defp gen_ports(port_no, _), do: [port_no]
end