Update App timestamp every new rating

lib/plexus/apps.ex

@@ -50,6 +50,14 @@ defmodule Plexus.Apps do
     |> Repo.one!()
   end
 
+  @spec fetch_app(String.t()) :: {:ok, App.t()} | {:error, :not_found}
+  def fetch_app(package) do
+    case Repo.get(App, package) do
+      %App{} = app -> {:ok, app}
+      nil -> {:error, :not_found}
+    end
+  end
+
   @spec create_app(%{
           optional(:icon_url) => String.t(),
           package: String.t(),

lib/plexus/ratings.ex

@@ -4,6 +4,7 @@ defmodule Plexus.Ratings do
   """
   import Ecto.Query
 
+  alias Plexus.Apps
   alias Plexus.PaginationHelpers
   alias Plexus.QueryHelpers
   alias Plexus.Repo
@@ -56,10 +57,13 @@ defmodule Plexus.Ratings do
           rating_type: atom(),
           score: pos_integer()
         }) :: {:ok, Rating.t()} | {:error, Ecto.Changeset.t()}
-  def create_rating(params) do
-    %Rating{}
-    |> Rating.changeset(params)
-    |> Repo.insert()
+  def create_rating(%{app_package: app_package} = params) do
+    Repo.transact(fn ->
+      with {:ok, app} <- Apps.fetch_app(app_package),
+           {:ok, _app} <- Apps.update_app(app, %{updated_at: DateTime.utc_now()}) do
+        Repo.insert(Rating.changeset(%Rating{}, params))
+      end
+    end)
     |> broadcast(:app_rating_updated)
   end
 

lib/plexus/schemas/app.ex

@@ -20,7 +20,7 @@ defmodule Plexus.Schemas.App do
   @spec changeset(App.t(), map()) :: Ecto.Changeset.t()
   def changeset(%App{} = app, params) do
     app
-    |> cast(params, [:package, :name, :icon_url])
+    |> cast(params, [:package, :name, :icon_url, :updated_at])
     |> validate_required([:package, :name])
     |> unique_constraint(:package, name: :apps_pkey)
   end

test/plexus/ratings_test.exs

@@ -8,7 +8,7 @@ defmodule Plexus.RatingsTest do
   alias Plexus.Schemas.Rating
 
   @invalid_attrs %{
-    app_package: nil,
+    app_package: "",
     app_build_number: nil,
     app_version: nil,
     rating_type: nil,
@@ -65,7 +65,7 @@ defmodule Plexus.RatingsTest do
     end
 
     test "invalid data returns error changeset" do
-      assert {:error, %Ecto.Changeset{}} = Ratings.create_rating(@invalid_attrs)
+      assert {:error, _reason} = Ratings.create_rating(@invalid_attrs)
     end
   end
 end