Add logic to backfill scrobbled_tracks

Chokes on duplicate primary keys

lib/last_fm/api.ex

@@ -51,11 +51,14 @@ defmodule LastFm.API do
     |> post_request()
   end
 
-  def get_recent_tracks(to_uts \\ nil, config) do
+  def get_recent_tracks(opts \\ [], config) do
+    to_uts = Keyword.get(opts, :to_uts)
+    limit = Keyword.get(opts, :limit, 50)
+
     params =
       config
       |> base_params()
-      |> Keyword.merge(method: "user.getrecenttracks", limit: 50)
+      |> Keyword.merge(method: "user.getrecenttracks", limit: limit)
 
     params = if to_uts, do: Keyword.put(params, :to, to_uts), else: params
 

lib/last_fm/import.ex

@@ -10,8 +10,8 @@ defmodule LastFm.Import do
     :last_fm_data
   ]
 
-  def batch(uts_to) do
-    with {:ok, tracks} <- LastFm.get_tracks(uts_to) do
+  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)

lib/last_fm/worker/backfill_scrobbled_tracks.ex

@@ -0,0 +1,29 @@
+defmodule LastFm.Worker.BackfillScrobbledTracks do
+  use Oban.Worker, queue: :heavy_writes, max_attempts: 3
+
+  alias MusicLibrary.BackgroundRepo
+
+  @backfill_delay 5
+  @batch_size 100
+
+  @impl Oban.Worker
+  def perform(%{args: %{"to_uts" => to_uts}}) do
+    # importing is an all or nothing operation, which means that we can
+    # use the returning count to determine if we reached the end of the backfilling
+    # process.
+    case LastFm.Import.batch(to_uts: to_uts, limit: @batch_size) do
+      {@batch_size, nil} ->
+        next_to_uts = LastFm.lowest_scrobbled_at_uts()
+
+        %{"to_uts" => next_to_uts}
+        |> new(schedule_in: @backfill_delay)
+        |> BackgroundRepo.insert()
+
+      {other_count, nil} when is_integer(other_count) ->
+        :ok
+
+      error ->
+        error
+    end
+  end
+end