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/downloading/media_downloader.ex

@@ -0,0 +1,65 @@
+defmodule Pinchflat.Downloading.MediaDownloader do
+  @moduledoc """
+  This is the integration layer for actually downloading media.
+  It takes into account the media profile's settings in order
+  to download the media with the desired options.
+  """
+
+  alias Pinchflat.Repo
+  alias Pinchflat.Media
+  alias Pinchflat.Media.MediaItem
+
+  alias Pinchflat.YtDlp.Media, as: YtDlpMedia
+  alias Pinchflat.Downloading.DownloadOptionBuilder, as: YtDlpDownloadOptionBuilder
+  alias Pinchflat.Metadata.MetadataParser, as: YtDlpMetadataParser
+  alias Pinchflat.Metadata.MetadataFileHelpers, as: YtDlpMetadataHelpers
+
+  @doc """
+  Downloads media for a media item, updating the media item based on the metadata
+  returned by yt-dlp. Also saves the entire metadata response to the associated
+  media_metadata record.
+
+  NOTE: related methods (like the download worker) won't download if the media item's source
+  is set to not download media. However, I'm not enforcing that here since I need this for testing.
+  This may change in the future but I'm not stressed.
+
+  Returns {:ok, %MediaItem{}} | {:error, any, ...any}
+  """
+  def download_for_media_item(%MediaItem{} = media_item) do
+    item_with_preloads = Repo.preload(media_item, [:metadata, source: :media_profile])
+
+    case download_with_options(media_item.original_url, item_with_preloads) do
+      {:ok, parsed_json} ->
+        {parser, helpers} = {YtDlpMetadataParser, YtDlpMetadataHelpers}
+
+        parsed_attrs =
+          parsed_json
+          |> parser.parse_for_media_item()
+          |> Map.merge(%{
+            media_downloaded_at: DateTime.utc_now(),
+            metadata: %{
+              metadata_filepath: helpers.compress_and_store_metadata_for(media_item, parsed_json),
+              thumbnail_filepath: helpers.download_and_store_thumbnail_for(media_item, parsed_json)
+            }
+          })
+
+        # Don't forgor to use preloaded associations or updates to
+        # associations won't work!
+        Media.update_media_item(item_with_preloads, parsed_attrs)
+
+      err ->
+        err
+    end
+  end
+
+  # def download_for_source(source, url) do
+  #   # Create MI from source and URL
+  #   media_item = nil
+  # end
+
+  defp download_with_options(url, item_with_preloads) do
+    {:ok, options} = YtDlpDownloadOptionBuilder.build(item_with_preloads)
+
+    YtDlpMedia.download(url, options)
+  end
+end