feat: use stop to route cache in alerts filter expansion

config/config.exs

@@ -485,6 +485,8 @@ config :screens, Screens.ScreenApiResponseCache,
   gc_interval: :timer.hours(1),
   allocated_memory: 250_000_000
 
+config :screens, Screens.Stops.StopsToRoutes, adapter: Nebulex.Adapters.Local
+
 # Import environment specific config. This must remain at the bottom
 # of this file so it overrides the configuration defined above.
 import_config "#{Mix.env()}.exs"

config/test.exs

@@ -26,7 +26,7 @@ config :screens,
   blue_bikes_station_information_url: [:no_api_requests_allowed_during_testing],
   blue_bikes_station_status_url: [:no_api_requests_allowed_during_testing],
   blue_bikes_api_client: Screens.BlueBikes.FakeClient,
-  alerts_cache_filter_route_mod: Screens.Routes.Route.Mock,
+  stops_to_routes_route_mod: Screens.Routes.Route.Mock,
   dup_headsign_replacements: %{
     "Test 1" => "T1"
   },
@@ -161,3 +161,5 @@ config :screens, :screens_by_alert,
   screens_by_alert_ttl_seconds: 2,
   screens_last_updated_ttl_seconds: 2,
   screens_ttl_seconds: 1
+
+config :screens, Screens.Stops.StopsToRoutes, adapter: Nebulex.Adapters.Nil

lib/screens/alerts/cache/filter.ex

@@ -2,12 +2,7 @@ defmodule Screens.Alerts.Cache.Filter do
   @moduledoc """
   Logic to apply filters to a list of `Screens.Alerts.Alert` structs.
   """
-
-  @route_mod Application.compile_env(
-               :screens,
-               :alerts_cache_filter_route_mod,
-               Screens.Routes.Route
-             )
+  alias Screens.Stops.StopsToRoutes
 
   @default_activities ~w[BOARD EXIT RIDE]
 
@@ -92,15 +87,10 @@ defmodule Screens.Alerts.Cache.Filter do
   end
 
   defp build_matcher({:stops, values}, acc) when is_list(values) do
-    routes =
-      values
-      |> Enum.flat_map(fn stop_id ->
-        {:ok, routes} = @route_mod.serving_stop(stop_id)
-        routes
-      end)
+    route_ids = StopsToRoutes.stops_to_routes(values)
 
     route_matchers =
-      for %{id: route_id} <- routes,
+      for route_id <- route_ids,
           stop_id <- [nil | values] do
         %{route: route_id, stop: stop_id}
       end

lib/screens/stops/stops_to_routes.ex

@@ -5,7 +5,9 @@ defmodule Screens.Stops.StopsToRoutes do
   """
   use Nebulex.Cache,
     otp_app: :screens,
-    adapter: Nebulex.Adapters.Local
+    adapter: Application.compile_env(:screens, [__MODULE__, :adapter])
+
+  @route_mod Application.compile_env(:screens, :stops_to_routes_route_mod, Screens.Routes.Route)
 
   @base_ttl :timer.hours(1)
 
@@ -20,7 +22,7 @@ defmodule Screens.Stops.StopsToRoutes do
       else
         from_api =
           for stop_id <- missing_stop_ids, into: %{} do
-            {:ok, routes} = fetch_routes_for_stops(stop_id)
+            {:ok, routes} = @route_mod.serving_stop(stop_id)
             route_ids = Enum.map(routes, & &1.id)
 
             {stop_id, route_ids}
@@ -37,11 +39,6 @@ defmodule Screens.Stops.StopsToRoutes do
     |> Enum.uniq()
   end
 
-  defp fetch_routes_for_stops(stop_ids) do
-    stop_impl = Application.get_env(:screens, :stops_to_routes_stop_mod, Screens.Stops.Stop)
-    stop_impl.fetch_routes_for_stops(stop_ids)
-  end
-
   defp ungroup_values(map) do
     map
     |> Map.values()