Revert "fix: disable the realtime LineAPI"

This reverts commit 5ff14ff. It also
moves the endpoint to a different route. This is so that any browsers
out there that still have the polling code will not be hitting this
endpoint.

apps/site/assets/ts/schedule/components/line-diagram/LineDiagram.tsx

@@ -92,7 +92,9 @@ const LineDiagram = ({
   });
 
   const { data: maybeLiveData } = useFetch(
-    `/schedules/line_api/realtime?id=${route.id}&direction_id=${directionId}`,
+    `/schedules/line_api/predictions_and_vehicles?id=${
+      route.id
+    }&direction_id=${directionId}`,
     {},
     { json: true, watch: directionId }
   );

apps/site/lib/site_web/controllers/schedule/line_api.ex

@@ -4,13 +4,24 @@ defmodule SiteWeb.ScheduleController.LineApi do
 
   alias Alerts.Stop, as: AlertsStop
   alias Routes.Route
+  alias Schedules.Repo, as: SchedulesRepo
+  alias Site.TransitNearMe
   alias SiteWeb.ScheduleController.Line.DiagramHelpers
   alias SiteWeb.ScheduleController.Line.Helpers, as: LineHelpers
   alias Stops.Repo, as: StopsRepo
   alias Stops.RouteStop
+  alias Vehicles.Repo, as: VehiclesRepo
+  alias Vehicles.Vehicle
 
   import SiteWeb.StopController, only: [json_safe_alerts: 2]
 
+  @typep simple_vehicle :: %{
+           id: String.t(),
+           headsign: String.t() | nil,
+           status: String.t(),
+           trip_name: String.t() | nil
+         }
+
   @spec show(Plug.Conn.t(), map()) :: Plug.Conn.t()
   def show(conn, %{"id" => route_id, "direction_id" => direction_id}) do
     line_data =
@@ -38,12 +49,38 @@ defmodule SiteWeb.ScheduleController.LineApi do
   @doc """
   Provides predictions and vehicle information for a given route and direction, organized by stop.
   The line diagram polls this endpoint for its real-time data.
-
-  Currently disabled due to performance issues.
   """
-  @spec realtime(Plug.Conn.t(), map()) :: Plug.Conn.t()
-  def realtime(conn, _params) do
-    json(conn, %{})
+  @spec predictions_and_vehicles(Plug.Conn.t(), map()) :: Plug.Conn.t()
+  def predictions_and_vehicles(conn, %{"id" => route_id, "direction_id" => direction_id}) do
+    headsigns_by_stop =
+      TransitNearMe.time_data_for_route_by_stop(
+        route_id,
+        String.to_integer(direction_id),
+        date: conn.assigns.date,
+        now: conn.assigns.date_time
+      )
+
+    vehicles_by_stop =
+      route_id
+      |> expand_route_id()
+      |> Stream.flat_map(&VehiclesRepo.route(&1, direction_id: String.to_integer(direction_id)))
+      |> Stream.map(&update_vehicle_with_parent_stop(&1))
+      |> Enum.group_by(& &1.stop_id)
+
+    combined_data_by_stop =
+      Map.keys(headsigns_by_stop)
+      |> Stream.concat(Map.keys(vehicles_by_stop))
+      |> Stream.uniq()
+      |> Stream.map(fn stop_id ->
+        {stop_id,
+         %{
+           headsigns: Map.get(headsigns_by_stop, stop_id, []),
+           vehicles: Map.get(vehicles_by_stop, stop_id, []) |> Enum.map(&simple_vehicle_map(&1))
+         }}
+      end)
+      |> Enum.into(%{})
+
+    json(conn, combined_data_by_stop)
   end
 
   @spec update_route_stop_data({any, RouteStop.t()}, any, DateTime.t()) :: map()
@@ -55,6 +92,10 @@ defmodule SiteWeb.ScheduleController.LineApi do
     }
   end
 
+  @spec expand_route_id(Route.id_t()) :: [Route.id_t()]
+  defp expand_route_id("Green"), do: GreenLine.branch_ids()
+  defp expand_route_id(route_id), do: [route_id]
+
   @spec get_line_data(Route.id_t(), LineHelpers.direction_id(), Route.branch_name(), boolean()) ::
           [DiagramHelpers.stop_with_bubble_info()]
   defp get_line_data(route_id, direction_id, variant, redesign_enabled?) do
@@ -67,4 +108,28 @@ defmodule SiteWeb.ScheduleController.LineApi do
 
     DiagramHelpers.build_stop_list(branches, direction_id, redesign_enabled?)
   end
+
+  @spec simple_vehicle_map(Vehicle.t()) :: simple_vehicle
+  defp simple_vehicle_map(%Vehicle{id: id, status: status, trip_id: trip_id}) do
+    case SchedulesRepo.trip(trip_id) do
+      nil ->
+        %{id: id, status: status}
+
+      %{headsign: headsign, name: name} ->
+        %{
+          id: id,
+          headsign: headsign,
+          status: status,
+          trip_name: name
+        }
+    end
+  end
+
+  @spec update_vehicle_with_parent_stop(Vehicle.t()) :: Vehicle.t()
+  defp update_vehicle_with_parent_stop(vehicle) do
+    case StopsRepo.get_parent(vehicle.stop_id) do
+      nil -> vehicle
+      parent_stop -> %{vehicle | stop_id: parent_stop.id}
+    end
+  end
 end

apps/site/lib/site_web/router.ex

@@ -133,7 +133,13 @@ defmodule SiteWeb.Router do
     get("/schedules/schedule_api", ScheduleController.ScheduleApi, :show)
     get("/schedules/map_api", ScheduleController.MapApi, :show)
     get("/schedules/line_api", ScheduleController.LineApi, :show)
-    get("/schedules/line_api/realtime", ScheduleController.LineApi, :realtime)
+
+    get(
+      "/schedules/line_api/predictions_and_vehicles",
+      ScheduleController.LineApi,
+      :predictions_and_vehicles
+    )
+
     get("/schedules/subway", ModeController, :subway)
     get("/schedules/bus", ModeController, :bus)
     get("/schedules/ferry", ModeController, :ferry)

apps/site/test/site_web/controllers/line_api_test.exs

@@ -9,11 +9,15 @@ defmodule SiteWeb.LineApiTest do
     end
   end
 
-  describe "realtime" do
+  describe "predictions_and_vehicles" do
     test "success response", %{conn: conn} do
-      conn = get(conn, line_api_path(conn, :realtime, %{"id" => "Red", "direction_id" => "1"}))
+      conn =
+        get(
+          conn,
+          line_api_path(conn, :predictions_and_vehicles, %{"id" => "Red", "direction_id" => "1"})
+        )
 
-      assert %{} = json_response(conn, 200)
+      assert %{"place-brdwy" => %{"headsigns" => _, "vehicles" => _}} = json_response(conn, 200)
     end
   end
 end