[Enhancement] Support Multiple YouTube API Keys

lib/pinchflat/fast_indexing/youtube_api.ex

@@ -12,14 +12,16 @@ defmodule Pinchflat.FastIndexing.YoutubeApi do
 
   @behaviour YoutubeBehaviour
 
+  @agent_name {:global, __MODULE__.KeyIndex}
+
   @doc """
   Determines if the YouTube API is enabled for fast indexing by checking
   if the user has an API key set
 
   Returns boolean()
   """
   @impl YoutubeBehaviour
-  def enabled?(), do: is_binary(api_key())
+  def enabled?, do: Enum.any?(api_keys())
 
   @doc """
   Fetches the recent media IDs from the YouTube API for a given source.
@@ -74,16 +76,53 @@ defmodule Pinchflat.FastIndexing.YoutubeApi do
     |> FunctionUtils.wrap_ok()
   end
 
-  defp api_key do
-    Settings.get!(:youtube_api_key)
+  defp api_keys do
+    case Settings.get!(:youtube_api_key) do
+      nil ->
+        []
+
+      keys ->
+        keys
+        |> String.split(",")
+        |> Enum.map(&String.trim/1)
+        |> Enum.reject(&(&1 == ""))
+    end
+  end
+
+  defp get_or_start_api_key_agent do
+    case Agent.start(fn -> 0 end, name: @agent_name) do
+      {:ok, pid} -> pid
+      {:error, {:already_started, pid}} -> pid
+    end
+  end
+
+  # Gets the next API key in round-robin fashion
+  defp next_api_key do
+    keys = api_keys()
+
+    case keys do
+      [] ->
+        nil
+
+      keys ->
+        pid = get_or_start_api_key_agent()
+
+        current_index =
+          Agent.get_and_update(pid, fn current ->
+            {current, rem(current + 1, length(keys))}
+          end)
+
+        Logger.debug("Using YouTube API key: #{Enum.at(keys, current_index)}")
+        Enum.at(keys, current_index)
+    end
   end
 
   defp construct_api_endpoint(playlist_id) do
     api_base = "https://youtube.googleapis.com/youtube/v3/playlistItems"
     property_type = "contentDetails"
     max_results = 50
 
-    "#{api_base}?part=#{property_type}&maxResults=#{max_results}&playlistId=#{playlist_id}&key=#{api_key()}"
+    "#{api_base}?part=#{property_type}&maxResults=#{max_results}&playlistId=#{playlist_id}&key=#{next_api_key()}"
   end
 
   defp http_client do

lib/pinchflat_web/controllers/settings/setting_html/setting_form.html.heex

@@ -34,9 +34,9 @@
 
       <.input
         field={f[:youtube_api_key]}
-        placeholder="ABC123"
+        placeholder="ABC123,DEF456"
         type="text"
-        label="YouTube API Key"
+        label="YouTube API Key(s)"
         help={youtube_api_help()}
         html_help={true}
         inputclass="font-mono text-sm mr-4"

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"]