[Enhancement] Support Multiple YouTube API Keys (#606)

* feat: multiple YouTube API keys

* fix: requested changes

test/pinchflat/fast_indexing/youtube_api_test.exs

@@ -7,31 +7,67 @@ defmodule Pinchflat.FastIndexing.YoutubeApiTest do
   alias Pinchflat.FastIndexing.YoutubeApi
 
   describe "enabled?/0" do
-    test "returns true if the user has set a YouTube API key" do
+    test "returns true if the user has set YouTube API keys" do
+      Settings.set(youtube_api_key: "key1, key2")
+      assert YoutubeApi.enabled?()
+    end
+
+    test "returns true with a single API key" do
       Settings.set(youtube_api_key: "test_key")
 
       assert YoutubeApi.enabled?()
     end
 
-    test "returns false if the user has not set an API key" do
+    test "returns false if the user has not set any API keys" do
       Settings.set(youtube_api_key: nil)
+      refute YoutubeApi.enabled?()
+    end
 
+    test "returns false if only empty or whitespace keys are provided" do
+      Settings.set(youtube_api_key: "  ,  ,")
       refute YoutubeApi.enabled?()
     end
   end
 
   describe "get_recent_media_ids/1" do
     setup do
+      case :global.whereis_name(YoutubeApi.KeyIndex) do
+        :undefined -> :ok
+        pid -> Agent.stop(pid)
+      end
+
       source = source_fixture()
-      Settings.set(youtube_api_key: "test_key")
+      Settings.set(youtube_api_key: "key1, key2")
 
       {:ok, source: source}
     end
 
+    test "rotates through API keys", %{source: source} do
+      expect(HTTPClientMock, :get, fn url, _headers ->
+        assert url =~ "key=key1"
+        {:ok, "{}"}
+      end)
+
+      expect(HTTPClientMock, :get, fn url, _headers ->
+        assert url =~ "key=key2"
+        {:ok, "{}"}
+      end)
+
+      expect(HTTPClientMock, :get, fn url, _headers ->
+        assert url =~ "key=key1"
+        {:ok, "{}"}
+      end)
+
+      # three calls to verify rotation
+      YoutubeApi.get_recent_media_ids(source)
+      YoutubeApi.get_recent_media_ids(source)
+      YoutubeApi.get_recent_media_ids(source)
+    end
+
     test "calls the expected URL", %{source: source} do
       expect(HTTPClientMock, :get, fn url, headers ->
         api_base = "https://youtube.googleapis.com/youtube/v3/playlistItems"
-        request_url = "#{api_base}?part=contentDetails&maxResults=50&playlistId=#{source.collection_id}&key=test_key"
+        request_url = "#{api_base}?part=contentDetails&maxResults=50&playlistId=#{source.collection_id}&key=key1"
 
         assert url == request_url
         assert headers == [accept: "application/json"]