Extract ExternalLink module

lib/music_brainz/external_link.ex

@@ -0,0 +1,28 @@
+defmodule MusicBrainz.ExternalLink do
+  defstruct [:name, :url]
+
+  def external_links(musicbrainz_data, patterns) when is_map(patterns) do
+    Enum.reduce(patterns, [], fn {name, pattern}, acc ->
+      case external_links(musicbrainz_data, pattern) do
+        [] ->
+          acc
+
+        [url | _rest] ->
+          [%__MODULE__{name: name, url: url} | acc]
+      end
+    end)
+  end
+
+  def external_links(musicbrainz_data, pattern) do
+    case get_in(musicbrainz_data, ["relations", Access.all(), "url", "resource"]) do
+      nil -> []
+      urls -> filter_urls(urls, pattern)
+    end
+  end
+
+  defp filter_urls(urls, nil), do: urls
+
+  defp filter_urls(urls, pattern) do
+    Enum.filter(urls, fn url -> String.contains?(url, pattern) end)
+  end
+end