Filter flex resuls also by sort order

src/main/java/org/opentripplanner/model/plan/SortOrder.java

@@ -42,4 +42,16 @@ public enum SortOrder {
   public boolean isSortedByAscendingArrivalTime() {
     return this == STREET_AND_ARRIVAL_TIME;
   }
+
+  /**
+   * The itineraries are sorted with by departure time with the latest departure time first. When
+   * paging we need to know which end of the list of itineraries we should crop. This method is used
+   * to decide that together with the current page type (next/previous).
+   * <p>
+   * This returns {@code false} for the default depart-after search, and {@code true} for an
+   * arrive-by search.
+   */
+  public boolean isSortedByDescendingDepartureTime() {
+    return this == STREET_AND_DEPARTURE_TIME;
+  }
 }

src/main/java/org/opentripplanner/routing/algorithm/filterchain/ItineraryListFilterChainBuilder.java

@@ -473,7 +473,10 @@ public ItineraryListFilterChain build() {
       }
 
       if (earliestDepartureTime != null && filterDirectFlexByEarliestDeparture) {
-        addRemoveFilter(filters, new FlexSearchWindowFilter(earliestDepartureTime));
+        addRemoveFilter(
+          filters,
+          new FlexSearchWindowFilter(earliestDepartureTime, searchWindow, sortOrder)
+        );
       }
 
       // Remove itineraries present in the page retrieved before this page/search.

src/main/java/org/opentripplanner/routing/algorithm/filterchain/filters/system/FlexSearchWindowFilter.java

@@ -1,8 +1,10 @@
 package org.opentripplanner.routing.algorithm.filterchain.filters.system;
 
+import java.time.Duration;
 import java.time.Instant;
 import java.util.function.Predicate;
 import org.opentripplanner.model.plan.Itinerary;
+import org.opentripplanner.model.plan.SortOrder;
 import org.opentripplanner.routing.algorithm.filterchain.framework.spi.RemoveItineraryFlagger;
 
 /**
@@ -18,9 +20,17 @@ public class FlexSearchWindowFilter implements RemoveItineraryFlagger {
   public static final String TAG = "outside-flex-window";
 
   private final Instant earliestDepartureTime;
-
-  public FlexSearchWindowFilter(Instant earliestDepartureTime) {
+  private final Instant latestArrivalTime;
+  private final SortOrder sortOrder;
+
+  public FlexSearchWindowFilter(
+    Instant earliestDepartureTime,
+    Duration searchWindow,
+    SortOrder sortOrder
+  ) {
     this.earliestDepartureTime = earliestDepartureTime;
+    this.latestArrivalTime = earliestDepartureTime.plus(searchWindow);
+    this.sortOrder = sortOrder;
   }
 
   @Override
@@ -31,9 +41,12 @@ public String name() {
   @Override
   public Predicate<Itinerary> shouldBeFlaggedForRemoval() {
     return it -> {
-      if (it.isDirectFlex()) {
+      if (it.isDirectFlex() && sortOrder.isSortedByDescendingDepartureTime()) {
         var time = it.startTime().toInstant();
         return time.isBefore(earliestDepartureTime);
+      } else if (it.isDirectFlex() && sortOrder.isSortedByAscendingArrivalTime()) {
+        var time = it.startTime().toInstant();
+        return time.isAfter(latestArrivalTime);
       } else {
         return false;
       }

src/test/java/org/opentripplanner/routing/algorithm/filterchain/filters/system/FlexSearchWindowFilterTest.java

@@ -1,14 +1,17 @@
 package org.opentripplanner.routing.algorithm.filterchain.filters.system;
 
 import static com.google.common.truth.Truth.assertThat;
+import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.opentripplanner.framework.time.TimeUtils.time;
 import static org.opentripplanner.model.plan.TestItineraryBuilder.newItinerary;
 
+import java.time.Duration;
 import java.time.Instant;
 import java.util.List;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.ValueSource;
 import org.opentripplanner.model.plan.PlanTestConstants;
+import org.opentripplanner.model.plan.SortOrder;
 import org.opentripplanner.model.plan.TestItineraryBuilder;
 
 class FlexSearchWindowFilterTest implements PlanTestConstants {
@@ -19,9 +22,13 @@ class FlexSearchWindowFilterTest implements PlanTestConstants {
 
   @ParameterizedTest
   @ValueSource(strings = { "09:20", "09:21", "13:20" })
-  void keepFlexItinerariesAfterLDT(String startTime) {
+  void keepArriveByFlexItinerariesAfterEDT(String startTime) {
     var edt = "9:20";
-    var subject = new FlexSearchWindowFilter(TestItineraryBuilder.newTime(time(edt)).toInstant());
+    var subject = new FlexSearchWindowFilter(
+      TestItineraryBuilder.newTime(time(edt)).toInstant(),
+      Duration.ofMinutes(30),
+      SortOrder.STREET_AND_DEPARTURE_TIME
+    );
 
     var itin = newItinerary(A, time(startTime))
       .flex(T11_00, T11_30, B)
@@ -33,8 +40,12 @@ void keepFlexItinerariesAfterLDT(String startTime) {
 
   @ParameterizedTest
   @ValueSource(strings = { "00:00", "00:01", "09:19" })
-  void removeFlexItinerariesBeforeLDT(String startTime) {
-    var subject = new FlexSearchWindowFilter(LATEST_DEPARTURE_TIME);
+  void removeArriveByFlexItinerariesBeforeEDT(String startTime) {
+    var subject = new FlexSearchWindowFilter(
+      LATEST_DEPARTURE_TIME,
+      Duration.ofMinutes(30),
+      SortOrder.STREET_AND_DEPARTURE_TIME
+    );
 
     var itin = newItinerary(A, time(startTime))
       .flex(T11_00, T11_30, B)
@@ -43,4 +54,21 @@ void removeFlexItinerariesBeforeLDT(String startTime) {
 
     assertThat(subject.flagForRemoval(List.of(itin))).isEmpty();
   }
+
+  @ParameterizedTest
+  @ValueSource(strings = { "12:00" })
+  void removeDepartAtFlexItinerariesAfterLAT(String startTime) {
+    var subject = new FlexSearchWindowFilter(
+      LATEST_DEPARTURE_TIME,
+      Duration.ofMinutes(30),
+      SortOrder.STREET_AND_ARRIVAL_TIME
+    );
+
+    var itin = newItinerary(A, time(startTime))
+      .flex(T11_00, T11_30, B)
+      .withIsSearchWindowAware(false)
+      .build();
+
+    assertEquals(subject.flagForRemoval(List.of(itin)), List.of(itin));
+  }
 }