defmodule FeedParser.Parser.RSSInJSON do
  @moduledoc """
  A `FeedParser.Parser` that handles [RSS-in-JSON feeds](https://github.com/scripting/Scripting-News/blob/2347bb8751d94dc76d25074997db4fde682585f9/rss-in-json/README.md).
  """

  @behaviour FeedParser.Parser

  @impl FeedParser.Parser
  def accepts(data, content_type) do
    with "application/json" <- content_type,
         {:ok, json} <- Poison.decode(data),
         %{"rss" => %{"version" => "2.0"} = rss} <- json do
      {true, rss}
    else
      _ ->
        false
    end
  end

  @impl FeedParser.Parser
  def parse_feed(rss) do
    channel = rss["channel"]
    title = channel["title"]
    link = channel["link"]

    last_updated =
      channel["lastBuildDate"]
      |> Timex.parse("{RFC1123}")
      |> case do
        {:ok, date} -> date
        _ -> nil
      end

    image =
      case channel do
        %{"image" => %{"url" => url}} -> url
        _ -> nil
      end

    items =
      channel["item"]
      |> Enum.map(fn item ->
        guid = item["guid"]
        link = item["link"]
        title = Map.get(item, "title")
        content = item["description"]

        pubDate =
          item["pubDate"]
          |> Timex.parse("{RFC1123}")
          |> case do
            {:ok, date} -> date
            _ -> nil
          end

        %FeedParser.Item{
          guid: guid,
          url: link,
          links: [{link, nil}],
          title: title,
          content: content,
          date: pubDate
        }
      end)

    {:ok,
     %FeedParser.Feed{
       site_url: link,
       title: title,
       image_url: image,
       last_updated: last_updated,
       items: items
     }}
  end
end