refactor: add "representative headsigns"

This is in support of the new "real-time destinations" logic. * RoutePatterns now have a `headsign`, which is the headsign of their representative trip. * Trips now have a `pattern_headsign`, which is the headsign of their route pattern (if they have one), and a `representative_headsign` accessor, which returns the pattern headsign if there is one and the regular headsign if not. * Departures now have a `representative_headsign` accessor, which delegates to the same-named accessor on the Trip of either their Prediction or Schedule, as appropriate.
mbta · Oct 11, 2024 · 68b3470 · 68b3470
1 parent 14d43df
commit 68b3470
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Showing 10 changed files with 89 additions and 30 deletions.
diff --git a/lib/screens/predictions/parser.ex b/lib/screens/predictions/parser.ex
@@ -30,7 +30,7 @@ defmodule Screens.Predictions.Parser do
         },
         included
       ) do
-    trip = included |> Map.fetch!({trip_id, "trip"}) |> Trips.Parser.parse_trip()
+    trip = included |> Map.fetch!({trip_id, "trip"}) |> Trips.Parser.parse_trip(included)
     stop = included |> Map.fetch!({stop_id, "stop"}) |> Stops.Parser.parse_stop()
     route = included |> Map.fetch!({route_id, "route"}) |> Routes.Parser.parse_route(included)
 

diff --git a/lib/screens/predictions/prediction.ex b/lib/screens/predictions/prediction.ex
@@ -38,7 +38,10 @@ defmodule Screens.Predictions.Prediction do
         query_params,
         "predictions",
         Screens.Predictions.Parser,
-        %{include: ~w[alerts route.line stop trip.stops vehicle]}
+        %{
+          include:
+            ~w[alerts route.line stop trip.route_pattern.representative_trip trip.stops vehicle]
+        }
       )
 
     case predictions do

diff --git a/lib/screens/route_patterns/parser.ex b/lib/screens/route_patterns/parser.ex
@@ -28,25 +28,24 @@ defmodule Screens.RoutePatterns.Parser do
          },
          included
        ) do
+    %{
+      "attributes" => %{"headsign" => headsign},
+      "relationships" => %{"stops" => %{"data" => stop_references}}
+    } = Map.fetch!(included, {representative_trip_id, "trip"})
+
+    stops =
+      Enum.map(stop_references, fn %{"id" => stop_id} ->
+        included |> Map.fetch!({stop_id, "stop"}) |> Stops.Parser.parse_stop()
+      end)
+
     %RoutePattern{
       id: id,
       canonical?: canonical?,
       direction_id: direction_id,
       typicality: typicality,
       route: included |> Map.fetch!({route_id, "route"}) |> Routes.Parser.parse_route(included),
-      stops:
-        included
-        |> Map.fetch!({representative_trip_id, "trip"})
-        |> parse_representative_stops(included)
+      headsign: headsign,
+      stops: stops
     }
   end
-
-  defp parse_representative_stops(
-         %{"relationships" => %{"stops" => %{"data" => stop_references}}},
-         included
-       ) do
-    Enum.map(stop_references, fn %{"id" => stop_id} ->
-      included |> Map.fetch!({stop_id, "stop"}) |> Stops.Parser.parse_stop()
-    end)
-  end
 end
diff --git a/lib/screens/route_patterns/route_pattern.ex b/lib/screens/route_patterns/route_pattern.ex
@@ -8,7 +8,7 @@ defmodule Screens.RoutePatterns.RoutePattern do
   alias Screens.Trips.Trip
   alias Screens.V3Api
 
-  defstruct ~w[id canonical? direction_id typicality route stops]a
+  defstruct ~w[id canonical? direction_id typicality route headsign stops]a
 
   @type id :: String.t()
   @type typicality :: 1 | 2 | 3 | 4 | 5
@@ -19,6 +19,7 @@ defmodule Screens.RoutePatterns.RoutePattern do
           direction_id: Trip.direction(),
           typicality: typicality(),
           route: Route.t(),
+          headsign: String.t(),
           stops: [Stop.t()]
         }
 

diff --git a/lib/screens/schedules/parser.ex b/lib/screens/schedules/parser.ex
@@ -30,7 +30,7 @@ defmodule Screens.Schedules.Parser do
          },
          included
        ) do
-    trip = included |> Map.fetch!({trip_id, "trip"}) |> Trips.Parser.parse_trip()
+    trip = included |> Map.fetch!({trip_id, "trip"}) |> Trips.Parser.parse_trip(included)
     stop = included |> Map.fetch!({stop_id, "stop"}) |> Stops.Parser.parse_stop()
     route = included |> Map.fetch!({route_id, "route"}) |> Routes.Parser.parse_route(included)
 

diff --git a/lib/screens/schedules/schedule.ex b/lib/screens/schedules/schedule.ex
@@ -36,7 +36,11 @@ defmodule Screens.Schedules.Schedule do
         query_params,
         "schedules",
         Screens.Schedules.Parser,
-        Map.put(extra_params, :include, ~w[route.line stop trip.stops])
+        Map.put(
+          extra_params,
+          :include,
+          ~w[route.line stop trip.route_pattern.representative_trip trip.stops]
+        )
       )
 
     case schedules do

diff --git a/lib/screens/trips/parser.ex b/lib/screens/trips/parser.ex
@@ -1,23 +1,59 @@
 defmodule Screens.Trips.Parser do
   @moduledoc false
 
-  def parse_trip(%{"id" => id, "attributes" => attributes, "relationships" => relationships}) do
-    %{"headsign" => headsign, "direction_id" => direction_id} = attributes
-    %{"route" => %{"data" => %{"id" => route_id}}} = relationships
+  alias Screens.Trips.Trip
+
+  def parse(%{"data" => data} = response) do
+    included =
+      response
+      |> Map.get("included", [])
+      |> Map.new(fn %{"id" => id, "type" => type} = resource -> {{id, type}, resource} end)
+
+    Enum.map(data, &parse_trip(&1, included))
+  end
+
+  def parse_trip(
+        %{
+          "id" => id,
+          "attributes" => %{"headsign" => headsign, "direction_id" => direction_id},
+          "relationships" => %{"route" => %{"data" => %{"id" => route_id}}} = relationships
+        },
+        included
+      ) do
+    # We do not fully parse the trip => route_pattern => representative_trip chain, as this would
+    # recurse infinitely. Instead we hoist up only the attributes we're interested in.
+    pattern_headsign =
+      case Map.get(relationships, "route_pattern") do
+        %{
+          "data" => %{
+            "relationships" => %{
+              "representative_trip" => %{"data" => %{"id" => representative_trip_id}}
+            }
+          }
+        } ->
+          included
+          |> Map.fetch!({representative_trip_id, "trip"})
+          |> Map.fetch!("attributes")
+          |> Map.fetch!("headsign")
+
+        _ ->
+          nil
+      end
 
     stops =
       case Map.get(relationships, "stops") do
-        %{"data" => stop_list} ->
-          Enum.map(stop_list, fn %{"id" => stop_id, "type" => "stop"} -> stop_id end)
+        %{"data" => stops_data} ->
+          Enum.map(stops_data, fn %{"id" => stop_id, "type" => "stop"} -> stop_id end)
 
         _ ->
           nil
       end
 
-    %Screens.Trips.Trip{
+    %Trip{
       id: id,
       direction_id: direction_id,
       headsign: headsign,
+      pattern_headsign: pattern_headsign,
       route_id: route_id,
       stops: stops
     }

diff --git a/lib/screens/trips/trip.ex b/lib/screens/trips/trip.ex
@@ -3,20 +3,23 @@ defmodule Screens.Trips.Trip do
 
   alias Screens.Stops.Stop
 
-  defstruct id: "",
-            direction_id: nil,
-            headsign: nil,
-            route_id: nil,
-            stops: nil
+  defstruct ~w[id direction_id headsign pattern_headsign route_id stops]a
 
   @type id :: String.t()
   @type direction :: 0 | 1
 
   @type t :: %__MODULE__{
           id: id,
           direction_id: direction(),
-          headsign: String.t() | nil,
+          headsign: String.t(),
+          pattern_headsign: String.t() | nil,
           route_id: String.t() | nil,
           stops: list(Stop.id()) | nil
         }
+
+  @spec representative_headsign(t()) :: String.t()
+  def representative_headsign(%__MODULE__{pattern_headsign: headsign}) when not is_nil(headsign),
+    do: headsign
+
+  def representative_headsign(%__MODULE__{headsign: headsign}), do: headsign
 end
diff --git a/lib/screens/v2/departure.ex b/lib/screens/v2/departure.ex
@@ -141,6 +141,13 @@ defmodule Screens.V2.Departure do
   def id(%__MODULE__{prediction: %Prediction{id: prediction_id}}), do: prediction_id
   def id(%__MODULE__{schedule: %Schedule{id: schedule_id}}), do: schedule_id
 
+  @spec representative_headsign(t()) :: String.t() | nil
+  def representative_headsign(%__MODULE__{prediction: %Prediction{trip: trip}}),
+    do: Trip.representative_headsign(trip)
+
+  def representative_headsign(%__MODULE__{schedule: %Schedule{trip: trip}}),
+    do: Trip.representative_headsign(trip)
+
   @spec route(t()) :: Route.t()
   def route(%__MODULE__{prediction: %Prediction{route: route}}), do: route
   def route(%__MODULE__{prediction: nil, schedule: %Schedule{route: route}}), do: route

diff --git a/test/screens/route_patterns/route_pattern_test.exs b/test/screens/route_patterns/route_pattern_test.exs
@@ -69,6 +69,7 @@ defmodule Screens.RoutePatterns.RoutePatternTest do
                 %{
                   "id" => "canonical-Blue-C1-0",
                   "type" => "trip",
+                  "attributes" => %{"headsign" => "Bowdoin"},
                   "relationships" => %{
                     "stops" => %{
                       "data" => [
@@ -81,6 +82,7 @@ defmodule Screens.RoutePatterns.RoutePatternTest do
                 %{
                   "id" => "65198154",
                   "type" => "trip",
+                  "attributes" => %{"headsign" => "Bowdoin"},
                   "relationships" => %{
                     "stops" => %{
                       "data" => [
@@ -172,6 +174,7 @@ defmodule Screens.RoutePatterns.RoutePatternTest do
           direction_id: 0,
           typicality: 1,
           route: blue_route,
+          headsign: "Bowdoin",
           stops: [wonderland, bowdoin]
         },
         %RoutePattern{
@@ -180,6 +183,7 @@ defmodule Screens.RoutePatterns.RoutePatternTest do
           direction_id: 0,
           typicality: 3,
           route: blue_route,
+          headsign: "Bowdoin",
           stops: [orient_heights, bowdoin]
         }
       ]
@@ -271,11 +275,13 @@ defmodule Screens.RoutePatterns.RoutePatternTest do
                 %{
                   "id" => "trip-blue",
                   "type" => "trip",
+                  "attributes" => %{"headsign" => "Bowdoin"},
                   "relationships" => %{"stops" => %{"data" => []}}
                 },
                 %{
                   "id" => "trip-bus-1",
                   "type" => "trip",
+                  "attributes" => %{"headsign" => "Nubian"},
                   "relationships" => %{"stops" => %{"data" => []}}
                 }
               ]