Refactor modules into contexts (#78)

* [WIP] break out a few contexts, start refactoring fast index modules

* [WIP] more contexts, this time around slow indexing and downloads

* [WIP] got all tests passing

* [WIP] Added moduledocs

* Built a genserver to rename old jobs on boot

* Added a module naming check; moved things around

* Fixed specs

lib/pinchflat/fast_indexing/youtube_rss.ex

@@ -0,0 +1,51 @@
+defmodule Pinchflat.FastIndexing.YoutubeRss do
+  @moduledoc """
+  Methods for interacting with YouTube RSS feeds
+  """
+
+  require Logger
+
+  alias Pinchflat.Sources.Source
+
+  @doc """
+  Fetches the recent media IDs from a YouTube RSS feed for a given source.
+
+  Returns {:ok, [binary()]} | {:error, binary()}
+  """
+  def get_recent_media_ids_from_rss(%Source{} = source) do
+    Logger.debug("Fetching recent media IDs from YouTube RSS feed for source: #{source.collection_id}")
+
+    case http_client().get(rss_url_for_source(source)) do
+      {:ok, response} ->
+        response = to_string(response)
+        media_id_regex = ~r/<yt:videoId>(.*?)<\/yt:videoId>/
+
+        # Don't get on me about using regex to search XML.
+        # The content is known, well-formed, and simple.
+        media_ids =
+          media_id_regex
+          |> Regex.scan(response)
+          |> Enum.map(fn [_, id] -> String.trim(id) end)
+          |> Enum.filter(&(String.length(&1) > 0))
+          |> Enum.uniq()
+
+        Logger.debug("Media ids fetched from RSS: #{inspect(media_ids)}")
+
+        {:ok, media_ids}
+
+      {:error, _reason} ->
+        {:error, "Failed to fetch RSS feed"}
+    end
+  end
+
+  defp rss_url_for_source(source) do
+    case source.collection_type do
+      :channel -> "https://www.youtube.com/feeds/videos.xml?channel_id=#{source.collection_id}"
+      :playlist -> "https://www.youtube.com/feeds/videos.xml?playlist_id=#{source.collection_id}"
+    end
+  end
+
+  defp http_client do
+    Application.get_env(:pinchflat, :http_client, Pinchflat.HTTP.HTTPClient)
+  end
+end