Add LastFm feed for a given user

lib/last_fm/api.ex

@@ -0,0 +1,111 @@
+defmodule LastFm.API do
+  require Logger
+
+  @base_url "http://ws.audioscrobbler.com/2.0/"
+
+  def get_recent_tracks(user, api_key) do
+    options = [
+      method: "user.getrecenttracks",
+      user: user,
+      api_key: api_key,
+      format: "json",
+      limit: 20
+    ]
+
+    url = @base_url <> "?" <> URI.encode_query(options)
+
+    Logger.debug("Fetching data from #{sanitize_url(url, api_key)}")
+
+    case json_get(url) do
+      {:ok, response} ->
+        {:ok,
+         response
+         |> get_in(["recenttracks", "track"])
+         |> parse_tracks()}
+
+      other ->
+        msg = "Failed to fetch data from #{sanitize_url(url, api_key)}, reason: #{inspect(other)}"
+        Logger.error(msg)
+        {:error, msg}
+    end
+  end
+
+  defp json_get(url) do
+    req =
+      Finch.build(:get, url, [
+        {"User-Agent", "MusicLibrary/0.1.0 ( cloud8421@gmail.com )"}
+      ])
+
+    case Finch.request(req, MusicLibrary.Finch) do
+      {:ok, response} when response.status == 200 ->
+        Jason.decode(response.body)
+
+      other ->
+        other
+    end
+  end
+
+  defmodule Artist do
+    defstruct [:musicbrainz_id, :name]
+  end
+
+  defmodule Album do
+    defstruct [:musicbrainz_id, :title]
+  end
+
+  defmodule Track do
+    @moduledoc """
+    Data is not always guaranteed:
+
+    - musicbrainz_id can be an empty string
+    """
+    defstruct [
+      :musicbrainz_id,
+      :title,
+      :artist,
+      :album,
+      :cover_url,
+      :scrobbled_at_uts,
+      :scrobbled_at_label
+    ]
+  end
+
+  defp parse_tracks(raw_tracks) do
+    Enum.map(raw_tracks, fn t ->
+      album = %Album{
+        musicbrainz_id: t["album"]["mbid"],
+        title: t["album"]["#text"]
+      }
+
+      artist = %Artist{
+        musicbrainz_id: t["artist"]["mbid"],
+        name: t["artist"]["#text"]
+      }
+
+      %Track{
+        musicbrainz_id: t["mbid"],
+        title: t["name"],
+        artist: artist,
+        album: album,
+        cover_url: parse_cover_url(t),
+        scrobbled_at_uts: parse_scrobble_at_uts(t),
+        scrobbled_at_label: t["date"]["#text"]
+      }
+    end)
+  end
+
+  defp parse_cover_url(track) do
+    track["image"]
+    |> Enum.find(%{"#text" => nil}, fn i -> i["size"] == "small" end)
+    |> Map.get("#text")
+  end
+
+  defp parse_scrobble_at_uts(track) do
+    track["date"]["uts"]
+    |> String.to_integer()
+  end
+
+  defp sanitize_url(url, api_key) do
+    String.replace(url, api_key, "<redacted_api_key>")
+  end
+end