open-pod/lib/podcast_feed/provider/archive/parser.ex

defmodule PodcastFeed.Provider.Archive.Parser do
  @moduledoc """
  This module provides a public API for fetching data from archive.org and convert them
  in a common podcast data structures.
  """

  alias PodcastFeed.Utility.Format
  alias __MODULE__

  @custom_metadata_url "https://archive.org/download/{identifier}/metadata.json"
  @archive_metadata_url "http://archive.org/metadata/{identifier}"
  @download_url "https://archive.org/download/{identifier}/{filename}"
  @podcast_link "https://archive.org/details/{identifier}"

  @custom_metadata_defaults %{
    "link" => nil,
    "image" => %{
      "url" => nil,
      "title" => nil,
      "link" => nil,
    },
    "category" => "",
    "explicit" => "no",
    "version" => "1",
  }

  @enforce_keys [:identifier]
  defstruct [:identifier, :podcast_data, :archive_metadata, custom_metadata: @custom_metadata_defaults]

  def by_identifier(identifier) do
    %Parser{identifier: identifier}
    |> enrich_with_archive_metadata()
    |> enrich_with_custom_metadata()
    |> to_podcast_feed_data()
  end

  def to_podcast_feed_data(token) do
    %{
      podcast: podcast_data(token),
      items: items_data(token)
    }
  end

  defp podcast_data(token = %{custom_metadata: custom, archive_metadata: %{"metadata" => metadata, "item_last_updated" => last_updated}}) do
    link = Format.compile(@podcast_link, identifier: token.identifier)
    %{
      title: metadata["title"],
      description: metadata["description"],
      webmaster: metadata["uploader"],
      managingEditor: metadata["uploader"],
      owner: %{
        name: metadata["creator"],
        email: metadata["uploader"],
      },
      keywords: metadata["subject"],
      pubDate: metadata["publicdate"] |> NaiveDateTime.from_iso8601!() |> DateTime.from_naive!("Etc/UTC"),
      lastBuildDate: last_updated |> DateTime.from_unix!(:second),
      author: metadata["creator"],
      language: metadata["language"],
      image: %{
        url: get_in(custom, ["image", "url"]) || fetch_cover(token),
        title: get_in(custom, ["image", "title"]) || metadata["title"],
        link: get_in(custom, ["image", "link"]) || link,
      },
      link: Map.get(custom, "link") || link,
      category: Map.get(custom, "category", ""),
      explicit: Map.get(custom, "explicit", "no"),
    }
  end

  defp items_data(%{identifier: identifier, archive_metadata: %{"files" => files}}) do
    files
    |> filter_audio_files()
    |> Enum.map(fn f -> to_feed_item(f, identifier, files) end)
  end

  defp fetch_custom_metadata(identifier) do
    custom_metadata_url = Format.compile(@custom_metadata_url, identifier: identifier)
    parse_custom_metadata_response(:hackney.get(custom_metadata_url, [], "", [follow_redirect: true]))
  end

  defp parse_custom_metadata_response({:ok, 200, _headers, client_ref}) do
    {:ok, custom_metadata_json} = :hackney.body(client_ref)
    custom_metadata_json
    |> String.split("\n")
    |> Enum.join()
    |> Jason.decode!()
  end
  defp parse_custom_metadata_response(_), do: @custom_metadata_defaults

  defp fetch_archive_metadata(identifier) do
    metadata_url = Format.compile(@archive_metadata_url, identifier: identifier)
    {:ok, 200, _headers, client_ref} = :hackney.get(metadata_url, [], "", [follow_redirect: true, connect_timeout: 30_000, recv_timeout: 30_000])
    {:ok, metadata_json} = :hackney.body(client_ref)
    metadata_json |> Jason.decode!()
  end

  defp filter_audio_files(files) do
    files |> Enum.filter(fn f -> Map.get(f, "format") =~ ~r/MP3/i end) #FIXME:! mp3, ogg, boh
  end

  defp to_feed_item(file, identifier, _files) do
    filename = Map.get(file, "name")
    %{
      title: file["title"],
      description: "",
      pubDate: file |> Map.get("mtime") |> Integer.parse() |> elem(0) |> DateTime.from_unix!(:second),
      link: download_url(identifier, filename),
      length: (file |> Map.get("length") |> Float.parse() |> elem(0)) |> trunc(),
      size: file |> Map.get("size"),
      summary: "",
      # image: download_url(identifier, fetch_image_of_audio(filename, files)),
      image: nil,
      keywords: file |> Map.take(["album", "artist", "genre"]) |> Map.values(),
      explicit: "no",
    }
  end

  defp fetch_cover(%{identifier: identifier, archive_metadata: %{"files" => files}}) do
    filename = files
    |> Enum.filter(fn f -> f["source"] == "original" end)
    |> Enum.filter(fn f -> f["format"] =~ ~r/JPG|JPEG|PNG|GIF/i end)
    |> List.first()
    |> case do
      nil -> nil
      file -> Map.get(file, "name")
    end

    download_url(identifier, filename)
  end

  # defp fetch_image_of_audio(audio_file, files) do
  #   files
  #   |> Enum.filter(fn
  #     %{"format" => format, "source" => "derivative", "original" => ^audio_file} ->
  #       format =~ ~r/JPG|JPEG|PNG|GIF/i
  #     _ -> nil
  #   end)
  #   |> fetch_image_of_audio()
  # end

  # defp fetch_image_of_audio(image_files) when is_list(image_files), do: fetch_image_of_audio(List.first(image_files))
  # defp fetch_image_of_audio(nil), do: nil
  # defp fetch_image_of_audio(image_file), do: image_file |> Map.get("name", nil)

  defp download_url(_identifier, nil), do: nil
  defp download_url(identifier, filename) do
    Format.compile(@download_url, identifier: identifier, filename: filename) |> URI.encode()
  end

  defp enrich_with_archive_metadata(token) do
    %Parser{token | archive_metadata: fetch_archive_metadata(token.identifier)}
  end

  defp enrich_with_custom_metadata(token) do
    %Parser{token | custom_metadata: fetch_custom_metadata(token.identifier)}
  end

end