Trip Planner [Fix]: Out of system transfer logic

lib/dotcom/trip_plan/fares.ex

@@ -32,12 +32,16 @@ defmodule Dotcom.TripPlan.Fares do
 
   defp add_fares({leg, 0}, 0, _), do: cents_for_leg(leg)
 
+  # credo:disable-for-next-line
   defp add_fares({leg, leg_index}, total, transit_legs) do
     # Look at this transit leg and previous transit leg(s)
     two_legs = transit_legs |> Enum.slice(leg_index - 1, 2)
     three_legs = transit_legs |> Enum.slice(leg_index - 2, 3)
     # If this is part of a free transfer, don't add fare
     cond do
+      Transfer.subway_transfer?(three_legs) ->
+        total
+
       Transfer.bus_to_subway_transfer?(three_legs) ->
         if total == cents_for_leg(List.first(three_legs)),
           do: total + 70,
@@ -46,6 +50,9 @@ defmodule Dotcom.TripPlan.Fares do
       Transfer.maybe_transfer?(three_legs) ->
         total
 
+      Transfer.subway_transfer?(two_legs) ->
+        total
+
       Transfer.subway_after_sl1_from_airport?(two_legs) ->
         total
 

lib/dotcom/trip_plan/transfer.ex

@@ -15,7 +15,7 @@ defmodule Dotcom.TripPlan.Transfer do
   # (can't be certain, as it depends on media used)!
   @single_ride_transfers %{
     :bus => [:subway, :bus],
-    :subway => [:subway, :bus],
+    :subway => [:bus],
     :express_bus => [:subway, :bus, :express_bus]
   }
 
@@ -34,12 +34,20 @@ defmodule Dotcom.TripPlan.Transfer do
 
   @doc "Searches a list of legs for evidence of an in-station subway transfer."
   @spec subway_transfer?([Leg.t()]) :: boolean
-  def subway_transfer?([first_leg, next_leg | _])
+  def subway_transfer?([first_leg, next_leg])
       when agency_name?(first_leg, "MBTA") and agency_name?(next_leg, "MBTA") do
     same_station?(first_leg.to, next_leg.from) and subway?(first_leg.route) and
       subway?(next_leg.route)
   end
 
+  def subway_transfer?([first_leg, next_leg, last_leg])
+      when agency_name?(first_leg, "MBTA") and agency_name?(next_leg, "MBTA") and
+             agency_name?(last_leg, "MBTA") do
+    same_station?(first_leg.to, next_leg.from) and subway?(first_leg.route) and
+      subway?(next_leg.route) and same_station?(next_leg.to, last_leg.from) and
+      subway?(last_leg.route)
+  end
+
   def subway_transfer?([_ | legs]), do: subway_transfer?(legs)
 
   def subway_transfer?(_), do: false

test/dotcom/trip_plan/fares_test.exs

@@ -101,6 +101,188 @@ defmodule Dotcom.TripPlan.FaresTest do
     end
   end
 
+  test "valid two leg subway transfers" do
+    start_leg =
+      build(:transit_leg,
+        from: build(:place, stop: build(:stop, parent_station: %{gtfs_id: "mock-start"})),
+        to: build(:place, stop: build(:stop, parent_station: %{gtfs_id: "mock-midA"})),
+        route:
+          build(:route,
+            agency: build(:agency, name: "MBTA"),
+            type: 0
+          )
+      )
+
+    end_leg =
+      build(:transit_leg,
+        from: build(:place, stop: build(:stop, parent_station: %{gtfs_id: "mock-midA"})),
+        to: build(:place, stop: build(:stop, parent_station: %{gtfs_id: "mock-end"})),
+        route:
+          build(:route,
+            agency: build(:agency, name: "MBTA"),
+            type: 0
+          )
+      )
+
+    one_subway_fare =
+      build(:itinerary,
+        legs:
+          build_list(1, :transit_leg,
+            route:
+              build(:route,
+                agency: build(:agency, name: "MBTA"),
+                type: 0
+              )
+          )
+      )
+      |> fare()
+
+    fare = build(:itinerary, legs: [start_leg, end_leg]) |> fare()
+    assert fare <= one_subway_fare
+  end
+
+  test "valid three leg subway transfers" do
+    start_leg =
+      build(:transit_leg,
+        from: build(:place, stop: build(:stop, parent_station: %{gtfs_id: "mock-start"})),
+        to: build(:place, stop: build(:stop, parent_station: %{gtfs_id: "mock-midA"})),
+        route:
+          build(:route,
+            agency: build(:agency, name: "MBTA"),
+            type: 0
+          )
+      )
+
+    mid_leg =
+      build(:transit_leg,
+        from: build(:place, stop: build(:stop, parent_station: %{gtfs_id: "mock-midA"})),
+        to: build(:place, stop: build(:stop, parent_station: %{gtfs_id: "mock-midB"})),
+        route:
+          build(:route,
+            agency: build(:agency, name: "MBTA"),
+            type: 0
+          )
+      )
+
+    end_leg =
+      build(:transit_leg,
+        from: build(:place, stop: build(:stop, parent_station: %{gtfs_id: "mock-midB"})),
+        to: build(:place, stop: build(:stop, parent_station: %{gtfs_id: "mock-end"})),
+        route:
+          build(:route,
+            agency: build(:agency, name: "MBTA"),
+            type: 0
+          )
+      )
+
+    one_subway_fare =
+      build(:itinerary,
+        legs:
+          build_list(1, :transit_leg,
+            route:
+              build(:route,
+                agency: build(:agency, name: "MBTA"),
+                type: 0
+              )
+          )
+      )
+      |> fare()
+
+    fare = build(:itinerary, legs: [start_leg, mid_leg, end_leg]) |> fare()
+    assert fare <= one_subway_fare
+  end
+
+  test "invalid two leg subway transfers (eg red <-> blue)" do
+    start_leg =
+      build(:transit_leg,
+        from: build(:place, stop: build(:stop, parent_station: %{gtfs_id: "mock-start"})),
+        to: build(:place, stop: build(:stop, parent_station: %{gtfs_id: "mock-midA"})),
+        route:
+          build(:route,
+            agency: build(:agency, name: "MBTA"),
+            type: 0
+          )
+      )
+
+    end_leg =
+      build(:transit_leg,
+        from: build(:place, stop: build(:stop, parent_station: %{gtfs_id: "mock-midB"})),
+        to: build(:place, stop: build(:stop, parent_station: %{gtfs_id: "mock-end"})),
+        route:
+          build(:route,
+            agency: build(:agency, name: "MBTA"),
+            type: 0
+          )
+      )
+
+    one_subway_fare =
+      build(:itinerary,
+        legs:
+          build_list(1, :transit_leg,
+            route:
+              build(:route,
+                agency: build(:agency, name: "MBTA"),
+                type: 0
+              )
+          )
+      )
+      |> fare()
+
+    fare = build(:itinerary, legs: [start_leg, end_leg]) |> fare()
+    assert fare > one_subway_fare
+  end
+
+  test "invalid three leg subway transfers (eg red <-> blue)" do
+    start_leg =
+      build(:transit_leg,
+        from: build(:place, stop: build(:stop, parent_station: %{gtfs_id: "mock-start"})),
+        to: build(:place, stop: build(:stop, parent_station: %{gtfs_id: "mock-midA"})),
+        route:
+          build(:route,
+            agency: build(:agency, name: "MBTA"),
+            type: 0
+          )
+      )
+
+    mid_leg =
+      build(:transit_leg,
+        from: build(:place, stop: build(:stop, parent_station: %{gtfs_id: "mock-midA"})),
+        to: build(:place, stop: build(:stop, parent_station: %{gtfs_id: "mock-midB"})),
+        route:
+          build(:route,
+            agency: build(:agency, name: "MBTA"),
+            type: 0
+          )
+      )
+
+    end_leg =
+      build(:transit_leg,
+        from: build(:place, stop: build(:stop, parent_station: %{gtfs_id: "mock-other"})),
+        to: build(:place, stop: build(:stop, parent_station: %{gtfs_id: "mock-end"})),
+        route:
+          build(:route,
+            agency: build(:agency, name: "MBTA"),
+            type: 0
+          )
+      )
+
+    one_subway_fare =
+      build(:itinerary,
+        legs:
+          build_list(1, :transit_leg,
+            route:
+              build(:route,
+                agency: build(:agency, name: "MBTA"),
+                type: 0
+              )
+          )
+      )
+      |> fare()
+
+    fare = build(:itinerary, legs: [start_leg, mid_leg, end_leg]) |> fare()
+    assert fare > one_subway_fare
+  end
+
   describe "cents_for_leg/1" do
     test "walking leg" do
       leg = build(:walking_leg)

test/dotcom/trip_plan/transfer_test.exs

@@ -59,10 +59,6 @@ defmodule Dotcom.TripPlan.TransferTest do
       refute [nil, bus_leg()] |> maybe_transfer?
     end
 
-    test "subway -> subway" do
-      assert [subway_leg(), subway_leg()] |> maybe_transfer?
-    end
-
     test "subway -> local bus" do
       assert [subway_leg(), bus_leg()] |> maybe_transfer?
     end