Use stored scrobbled tracks

lib/last_fm.ex

@@ -2,7 +2,7 @@ defmodule LastFm do
   alias LastFm.{API, Feed, Refresh, Scrobble, Track, Worker}
   alias MusicLibrary.{BackgroundRepo, Repo}
 
-  def get_scrobbled_tracks, do: Feed.all_tracks()
+  def get_scrobbled_tracks, do: Feed.all_tracks(100)
 
   def subscribe_to_feed, do: Feed.subscribe()
 

lib/last_fm/feed.ex

@@ -8,34 +8,44 @@ defmodule LastFm.Feed do
   to one track at a time, and the timestamp has second-level precision.
   """
 
-  @spec create_table!() :: :ok | no_return
-  def create_table! do
-    __MODULE__ = :ets.new(__MODULE__, [:ordered_set, :named_table, :public])
-    :ok
-  end
+  import Ecto.Query
+
+  @insertable_fields [
+    :musicbrainz_id,
+    :title,
+    :artist,
+    :album,
+    :cover_url,
+    :scrobbled_at_uts,
+    :scrobbled_at_label,
+    :last_fm_data
+  ]
 
   @spec update([LastFm.Track.t()]) :: :ok | no_return
   def update(tracks) do
-    data = Enum.map(tracks, fn t -> {t.scrobbled_at_uts, t} end)
+    track_params =
+      tracks
+      |> Enum.map(fn t -> Map.take(t, @insertable_fields) end)
+      |> Enum.map(&Map.to_list/1)
 
-    :ets.delete_all_objects(__MODULE__)
-    :ets.insert(__MODULE__, data)
+    # HACK: if two tracks happen to have the exact same scrobbled_at_uts,
+    # we move it by a sec.
+    MusicLibrary.Repo.insert_all(LastFm.Track, track_params,
+      on_conflict: :nothing,
+      conflict_target: [:scrobbled_at_uts, :title]
+    )
 
     Phoenix.PubSub.broadcast(LastFm.PubSub, "feed:update", %{tracks: tracks})
   end
 
-  @spec all_tracks() :: [LastFm.Track.t()]
-  def all_tracks do
-    m = [
-      {
-        {:_, :_},
-        [],
-        [{:element, 2, :"$_"}]
-      }
-    ]
+  @spec all_tracks(non_neg_integer()) :: [LastFm.Track.t()]
+  def all_tracks(limit) do
+    q =
+      from t in LastFm.Track,
+        order_by: {:desc, t.scrobbled_at_uts},
+        limit: ^limit
 
-    # reversing to get tracks in DESC order
-    :ets.select_reverse(__MODULE__, m)
+    MusicLibrary.Repo.all(q)
   end
 
   @spec subscribe() :: :ok

lib/last_fm/import.ex

@@ -1,28 +1,7 @@
 defmodule LastFm.Import do
-  @insertable_fields [
-    :musicbrainz_id,
-    :title,
-    :artist,
-    :album,
-    :cover_url,
-    :scrobbled_at_uts,
-    :scrobbled_at_label,
-    :last_fm_data
-  ]
-
   def batch(opts) do
     with {:ok, tracks} <- LastFm.get_tracks(opts) do
-      track_params =
-        tracks
-        |> Enum.map(fn t -> Map.take(t, @insertable_fields) end)
-        |> Enum.map(&Map.to_list/1)
-
-      # HACK: if two tracks happen to have the exact same scrobbled_at_uts,
-      # we move it by a sec.
-      MusicLibrary.Repo.insert_all(LastFm.Track, track_params,
-        on_conflict: :nothing,
-        conflict_target: [:scrobbled_at_uts, :title]
-      )
+      LastFm.Feed.update(tracks)
     end
   end
 end

lib/last_fm/supervisor.ex

@@ -7,8 +7,6 @@ defmodule LastFm.Supervisor do
 
   @impl true
   def init(config) do
-    :ok = LastFm.Feed.create_table!()
-
     children = [
       {Phoenix.PubSub, name: LastFm.PubSub},
       {LastFm.Refresh, config}

test/last_fm/feed_test.exs

@@ -1,5 +1,5 @@
 defmodule LastFm.FeedTest do
-  use ExUnit.Case, async: true
+  use MusicLibrary.DataCase
 
   alias LastFm.{Album, Artist, Feed, Track}
 
@@ -46,7 +46,13 @@ defmodule LastFm.FeedTest do
 
     test "it returns tracks in descending order of scrobble" do
       :ok = Feed.update([@track_two, @track_one])
-      assert [@track_two, @track_one] == Feed.all_tracks()
+      track_two_scrobbled_at_uts = @track_two.scrobbled_at_uts
+      track_one_scrobbled_at_uts = @track_one.scrobbled_at_uts
+
+      assert [
+               %{scrobbled_at_uts: ^track_two_scrobbled_at_uts},
+               %{scrobbled_at_uts: ^track_one_scrobbled_at_uts}
+             ] = Feed.all_tracks(10)
     end
   end
 end