[Enhancement] Ignore media based on user scripts (#330)

* Integrated pre-download callback for media items

* Refactored existing tests

* Docs, etc

lib/pinchflat/downloading/media_download_worker.ex

@@ -39,17 +39,14 @@ defmodule Pinchflat.Downloading.MediaDownloadWorker do
     - `quality_upgrade?`: re-downloads media, including the video. Does not force download
       if the source is set to not download media
 
-  Returns :ok | {:ok, %MediaItem{}} | {:error, any, ...any}
+  Returns :ok | {:error, any, ...any}
   """
   @impl Oban.Worker
   def perform(%Oban.Job{args: %{"id" => media_item_id} = args}) do
     should_force = Map.get(args, "force", false)
     is_quality_upgrade = Map.get(args, "quality_upgrade?", false)
 
-    media_item =
-      media_item_id
-      |> Media.get_media_item!()
-      |> Repo.preload(:source)
+    media_item = fetch_and_run_prevent_download_user_script(media_item_id)
 
     # If the source or media item is set to not download media, perform a no-op unless forced
     if (media_item.source.download_media && !media_item.prevent_download) || should_force do
@@ -62,6 +59,20 @@ defmodule Pinchflat.Downloading.MediaDownloadWorker do
     Ecto.StaleEntryError -> Logger.info("#{__MODULE__} discarded: media item #{media_item_id} stale")
   end
 
+  # If a user script exists and, when run, returns a non-zero exit code, prevent this and all future downloads
+  # of the media item.
+  defp fetch_and_run_prevent_download_user_script(media_item_id) do
+    media_item = Media.get_media_item!(media_item_id)
+
+    {:ok, media_item} =
+      case run_user_script(:media_pre_download, media_item) do
+        {:ok, _, exit_code} when exit_code != 0 -> Media.update_media_item(media_item, %{prevent_download: true})
+        _ -> {:ok, media_item}
+      end
+
+    Repo.preload(media_item, :source)
+  end
+
   defp download_media_and_schedule_jobs(media_item, is_quality_upgrade, should_force) do
     overwrite_behaviour = if should_force || is_quality_upgrade, do: :force_overwrites, else: :no_force_overwrites
     override_opts = [overwrite_behaviour: overwrite_behaviour]
@@ -74,9 +85,9 @@ defmodule Pinchflat.Downloading.MediaDownloadWorker do
             media_redownloaded_at: get_redownloaded_at(is_quality_upgrade)
           })
 
-        :ok = run_user_script(updated_media_item)
+        run_user_script(:media_downloaded, updated_media_item)
 
-        {:ok, updated_media_item}
+        :ok
 
       {:recovered, _} ->
         {:error, :retry}
@@ -112,9 +123,9 @@ defmodule Pinchflat.Downloading.MediaDownloadWorker do
 
   # NOTE: I like this pattern of using the default value so that I don't have to
   # define it in config.exs (and friends). Consider using this elsewhere.
-  defp run_user_script(media_item) do
+  defp run_user_script(event, media_item) do
     runner = Application.get_env(:pinchflat, :user_script_runner, UserScriptRunner)
 
-    runner.run(:media_downloaded, media_item)
+    runner.run(event, media_item)
   end
 end