Move asset pruning logic to Assets context

Closes #130

lib/music_library/assets.ex

@@ -56,6 +56,30 @@ defmodule MusicLibrary.Assets do
     )
   end
 
+  @doc """
+  Deletes all assets not referenced by any record cover or artist info image.
+  Returns the number of pruned assets.
+  """
+  @spec prune_unreferenced() :: non_neg_integer()
+  def prune_unreferenced do
+    # Note that SQLite doesn't support left joins on delete, so we do it in two steps.
+    asset_hashes =
+      from a in Asset,
+        left_join: r in MusicLibrary.Records.Record,
+        on: r.cover_hash == a.hash,
+        left_join: ai in MusicLibrary.Artists.ArtistInfo,
+        on: ai.image_data_hash == a.hash,
+        where: is_nil(r.id) and is_nil(ai.id),
+        select: a.hash
+
+    q =
+      from a in Asset,
+        where: a.hash in subquery(asset_hashes)
+
+    {count, nil} = Repo.delete_all(q)
+    count
+  end
+
   @spec track_total_cache_size() :: :ok
   def track_total_cache_size do
     :telemetry.execute(

lib/music_library/worker/prune_assets.ex

@@ -1,35 +1,17 @@
 defmodule MusicLibrary.Worker.PruneAssets do
-  use Oban.Worker, queue: :default, max_attempts: 3
+  @moduledoc """
+  Prunes unreferenced assets from the database.
+  """
 
-  import Ecto.Query
+  use Oban.Worker, queue: :default, max_attempts: 3
 
   require Logger
 
-  alias MusicLibrary.{
+  alias MusicLibrary.Assets
-    Artists.ArtistInfo,
-    Assets.Asset,
-    Records.Record,
-    Repo
-  }
 
   @impl Oban.Worker
   def perform(_) do
-    # Find all assets that are not referenced by any records or artist info
+    count = Assets.prune_unreferenced()
-    # Note that SQLite doesn't support left joins on delete, so we do it in two steps.
-    asset_hashes =
-      from a in Asset,
-        left_join: r in Record,
-        on: r.cover_hash == a.hash,
-        left_join: ai in ArtistInfo,
-        on: ai.image_data_hash == a.hash,
-        where: is_nil(r.id) and is_nil(ai.id),
-        select: a.hash
-
-    q =
-      from a in Asset,
-        where: a.hash in subquery(asset_hashes)
-
-    {count, nil} = Repo.delete_all(q)
 
     Logger.info(fn -> "Pruned #{count} unreferenced assets." end)
   end