From dc2d8bee0ab513bfce06386973570cac0bd07d8a Mon Sep 17 00:00:00 2001
From: Josh Larson <jlarson@mbta.com>
Date: Thu, 12 Dec 2024 14:25:32 -0500
Subject: [PATCH] fix: De-duplicate start and end locations when they're next
 to transit segments (#2264)

---
 lib/dotcom/trip_plan/leg_to_segment_helper.ex |  8 +++++
 .../trip_plan/leg_to_segment_helper_test.exs  | 33 +++++++++++++++++++
 2 files changed, 41 insertions(+)

diff --git a/lib/dotcom/trip_plan/leg_to_segment_helper.ex b/lib/dotcom/trip_plan/leg_to_segment_helper.ex
index 0b6c6bbc0c..a3c17f31e5 100644
--- a/lib/dotcom/trip_plan/leg_to_segment_helper.ex
+++ b/lib/dotcom/trip_plan/leg_to_segment_helper.ex
@@ -25,6 +25,10 @@ defmodule Dotcom.TripPlan.LegToSegmentHelper do
     {:transit_segment, leg}
   end
 
+  defp prepend_start_location([{:transit_segment, _} | _] = segments) do
+    segments
+  end
+
   defp prepend_start_location([{_, leg} | _] = segments) do
     [
       {:location_segment, %{time: leg.start, place: leg.from}}
@@ -32,6 +36,10 @@ defmodule Dotcom.TripPlan.LegToSegmentHelper do
     ]
   end
 
+  defp append_end_location([{:transit_segment, _} = last_segment]) do
+    [last_segment]
+  end
+
   defp append_end_location([{_, leg} = last_segment]) do
     [last_segment, {:location_segment, %{time: leg.stop, place: leg.to}}]
   end
diff --git a/test/dotcom/trip_plan/leg_to_segment_helper_test.exs b/test/dotcom/trip_plan/leg_to_segment_helper_test.exs
index bef92dfd1f..55e7ae01f4 100644
--- a/test/dotcom/trip_plan/leg_to_segment_helper_test.exs
+++ b/test/dotcom/trip_plan/leg_to_segment_helper_test.exs
@@ -20,4 +20,37 @@ defmodule Dotcom.TripPlan.LegToSegmentHelperTest do
                %Leg{mode: %PersonalDetail{}}
              ])
   end
+
+  test "does not prepend location if the first segment is transit" do
+    assert [
+             {:transit_segment, _},
+             {:walking_segment, _},
+             {:location_segment, _}
+           ] =
+             LegToSegmentHelper.legs_to_segments([
+               %Leg{mode: %TransitDetail{}},
+               %Leg{mode: %PersonalDetail{}}
+             ])
+  end
+
+  test "does not append location if the last segment is transit" do
+    assert [
+             {:location_segment, _},
+             {:walking_segment, _},
+             {:transit_segment, _}
+           ] =
+             LegToSegmentHelper.legs_to_segments([
+               %Leg{mode: %PersonalDetail{}},
+               %Leg{mode: %TransitDetail{}}
+             ])
+  end
+
+  test "works if there is just one transit leg" do
+    assert [
+             {:transit_segment, _}
+           ] =
+             LegToSegmentHelper.legs_to_segments([
+               %Leg{mode: %TransitDetail{}}
+             ])
+  end
 end