feat: Breadcrumbs for new line diagram page

lib/dotcom_web/hooks/assign_route.ex

@@ -0,0 +1,23 @@
+defmodule DotcomWeb.Hooks.AssignRoute do
+  @moduledoc """
+  Assign the route, before both disconnected and connected mounts.
+  """
+  import Phoenix.Component, only: [assign: 3]
+
+  @routes_repo Application.compile_env!(:dotcom, :repo_modules)[:routes]
+
+  @doc """
+  Uses the route ID in the params to look up the corresponding
+  route, and assigns that route to the socket as `:route`.
+
+  If the route doesn't exist, then raises a
+  `DotcomWeb.NotFoundError` in order to get
+  `DotcomWeb.Router.handle_errors/2` to render the 404 page.
+  """
+  def on_mount(:default, %{"route_id" => route_id}, _session, socket) do
+    case @routes_repo.get(route_id) do
+      nil -> raise DotcomWeb.NotFoundError
+      route -> {:cont, assign(socket, :route, route)}
+    end
+  end
+end

lib/dotcom_web/hooks/breadcrumbs.ex

@@ -2,6 +2,7 @@ defmodule DotcomWeb.Hooks.Breadcrumbs do
   @moduledoc """
   Assign the breadcrumbs, before both disconnected and connected mounts.
   """
+  alias DotcomWeb.Schedule.RouteBreadcrumbs
 
   use Dotcom.Gettext.Sigils
   use DotcomWeb, :verified_routes
@@ -17,6 +18,10 @@ defmodule DotcomWeb.Hooks.Breadcrumbs do
     {:cont, assign(socket, :breadcrumbs, [build(~t"Trip Planner")])}
   end
 
+  def on_mount(:schedule_page, _params, _session, %{assigns: %{route: route}} = socket) do
+    {:cont, assign(socket, :breadcrumbs, RouteBreadcrumbs.breadcrumbs(route))}
+  end
+
   # catch-all case
   def on_mount(:default, _params, _session, socket), do: {:cont, socket}
 end

lib/dotcom_web/live/line_diagram_live.ex

@@ -5,7 +5,6 @@ defmodule DotcomWeb.LineDiagramLive do
 
   use DotcomWeb, :live_view
   @route_patterns_repo Application.compile_env!(:dotcom, :repo_modules)[:route_patterns]
-  @routes_repo Application.compile_env!(:dotcom, :repo_modules)[:routes]
   @alerts_repo Application.compile_env!(:dotcom, :repo_modules)[:alerts]
   @date_time_module Application.compile_env!(:dotcom, :date_time_module)
 
@@ -22,9 +21,12 @@ defmodule DotcomWeb.LineDiagramLive do
 
   import DotcomWeb.Views.Helpers.AlertHelpers, only: [alert_badge: 1]
 
+  on_mount DotcomWeb.Hooks.AssignRoute
+  on_mount {DotcomWeb.Hooks.Breadcrumbs, :schedule_page}
+
   def mount(params, _session, socket) do
-    route_id = params |> Map.get("route_id")
-    route = @routes_repo.get(route_id)
+    route = socket.assigns.route
+    route_id = route.id
     route_patterns = @route_patterns_repo.by_route_id(route_id)
 
     direction_id =