[traffxml] Fix location matching on dual carriageway roads

Signed-off-by: mvglasow <michael -at- vonglasow.com>

routing/index_router.cpp

@@ -1406,7 +1406,7 @@ bool IndexRouter::PointsOnEdgesSnapping::FindBestEdges(
     }
 
     // Removing all candidates which are fenced off by the road graph (|closestRoads|) from |checkpoint|.
-    return !IsFencedOff(checkpoint, edgeProj, closestRoads);
+    return !m_router.IsFakeEndingSetSimplified() || !IsFencedOff(checkpoint, edgeProj, closestRoads);
   };
 
   // Getting closest edges from |closestRoads| if they are correct according to isGood() function.

routing/index_router.hpp

@@ -136,6 +136,24 @@ protected:
               std::shared_ptr<NumMwmIds> numMwmIds, std::unique_ptr<m4::Tree<NumMwmId>> numMwmTree,
               std::shared_ptr<EdgeEstimator> estimator, DataSource & dataSource);
 
+
+  /**
+   * @brief Whether the set of fake endings generated for the check points is restricted.
+   *
+   * The return value is used internally when snapping checkpoints to edges. If this function
+   * returns true, this instructs the `PointsOnEdgesSnapping` instance to consider only edges which
+   * are not fenced off, i.e. can be reached from the respective checkpoint without crossing any
+   * other edges. If it returns false, this restriction does not apply, and all nearby edges are
+   * considered.
+   *
+   * Restricting the set of fake endings in this manner decreases the options considered for routing
+   * and thus processing time, which is desirable for regular routing and has no side effects.
+   *
+   * The `IndexRouter` implementation always returns true; subclasses may override this method and
+   * return different values.
+   */
+  virtual bool IsFakeEndingSetSimplified() { return true; }
+
 private:
   RouterResultCode CalculateSubrouteJointsMode(IndexGraphStarter & starter,
                                                RouterDelegate const & delegate,

traffxml/traff_decoder.hpp

@@ -188,6 +188,31 @@ public:
                   std::unique_ptr<m4::Tree<routing::NumMwmId>> numMwmTree,
                   DataSource & dataSource);
   protected:
+    /**
+     * @brief Whether the set of fake endings generated for the check points is restricted.
+     *
+     * The return value is used internally when snapping checkpoints to edges. If this function
+     * returns true, this instructs the `PointsOnEdgesSnapping` instance to consider only edges which
+     * are not fenced off, i.e. can be reached from the respective checkpoint without crossing any
+     * other edges. If it returns false, this restriction does not apply, and all nearby edges are
+     * considered.
+     *
+     * Restricting the set of fake endings in this manner decreases the options considered for routing
+     * and thus processing time, which is desirable for regular routing and has no side effects.
+     * For TraFF location matching, simplification has undesirable side effects: if reference points
+     * are located on one side of the road, the other carriageway may not be considered. This would
+     * lead to situations like these:
+     *
+     * --<--<-+<==<==<==<==<==<==<==<==<==<==<==<==<==<==<==<==<==<==<==<==<==<==<==<==<==<+-<--<--
+     * -->-->-+>==>==>==>==>==>==>-->-->-->-->-->-->-->-->-->-->-->==>==>==>==>==>==>==>==>+->-->--
+     *                          *<                               <*
+     *
+     * (-- carriageway, + junction, < > direction, *< end point, <* start point, == route)
+     *
+     * To avoid this, the `DecoderRouter` implementation always returns false.
+     */
+    bool IsFakeEndingSetSimplified() override { return false; }
+
   private:
   };