roundabout for segregated entry roads

src/extractor/guidance/intersection_generator.cpp

@@ -208,6 +208,15 @@ Intersection IntersectionGenerator::mergeSegregatedRoads(Intersection intersecti
     if (intersection.size() == 1)
         return intersection;
 
+    const bool is_connected_to_roundabout = [this,&intersection]() {
+        for (const auto &road : intersection)
+        {
+            if (node_based_graph.GetEdgeData(road.turn.eid).roundabout)
+                return true;
+        }
+        return false;
+    }();
+
     // check for merges including the basic u-turn
     // these result in an adjustment of all other angles
     if (mergable(0, intersection.size() - 1))
@@ -216,8 +225,24 @@ Intersection IntersectionGenerator::mergeSegregatedRoads(Intersection intersecti
             (360 - intersection[intersection.size() - 1].turn.angle) / 2;
         for (std::size_t i = 1; i + 1 < intersection.size(); ++i)
             intersection[i].turn.angle += correction_factor;
+
+        // FIXME if we have a left-sided country, we need to switch this off and enable it below
         intersection[0] = merge(intersection.front(), intersection.back());
         intersection[0].turn.angle = 0;
+
+        if (is_connected_to_roundabout)
+        {
+            // We are merging a u-turn against the direction of a roundabout
+            //
+            //    -----------> roundabout
+            //       /    \
+            //    out      in
+            //
+            // These cases have to be disabled, even if they are not forbidden specifically by a
+            // relation
+            intersection[0].entry_allowed = false;
+        }
+
         intersection.pop_back();
     }
 

src/extractor/guidance/roundabout_handler.cpp

@@ -37,6 +37,7 @@ bool RoundaboutHandler::canProcess(const NodeID from_nid,
 Intersection RoundaboutHandler::
 operator()(const NodeID from_nid, const EdgeID via_eid, Intersection intersection) const
 {
+    invalidateExitAgainstDirection(from_nid, via_eid, intersection);
     const auto flags = getRoundaboutFlags(from_nid, via_eid, intersection);
     const bool is_rotary = isRotary(node_based_graph.GetTarget(via_eid));
     // find the radius of the roundabout
@@ -55,7 +56,7 @@ detail::RoundaboutFlags RoundaboutHandler::getRoundaboutFlags(
     {
         const auto &edge_data = node_based_graph.GetEdgeData(road.turn.eid);
         // only check actual outgoing edges
-        if (edge_data.reversed)
+        if (edge_data.reversed || !road.entry_allowed )
             continue;
 
         if (edge_data.roundabout)
@@ -79,6 +80,42 @@ detail::RoundaboutFlags RoundaboutHandler::getRoundaboutFlags(
     return {on_roundabout, can_enter_roundabout, can_exit_roundabout_separately};
 }
 
+void RoundaboutHandler::invalidateExitAgainstDirection(const NodeID from_nid,
+                                                       const EdgeID via_eid,
+                                                       Intersection &intersection) const
+{
+    const auto &in_edge_data = node_based_graph.GetEdgeData(via_eid);
+    if( in_edge_data.roundabout )
+        return;
+
+    bool past_roundabout_angle = false;
+    for (auto &road : intersection)
+    {
+        const auto &edge_data = node_based_graph.GetEdgeData(road.turn.eid);
+        // only check actual outgoing edges
+        if (edge_data.reversed)
+        {
+            // remember whether we have seen the roundabout in-part
+            if (edge_data.roundabout)
+                past_roundabout_angle = true;
+
+            continue;
+        }
+
+        // Exiting roundabouts at an entry point is technically a data-modelling issue.
+        // This workaround handles cases in which an exit precedes and entry. The resulting
+        // u-turn against the roundabout direction is invalidated.
+        // The sorting of the angles represents a problem for left-sided driving, though.
+        // FIXME in case of left-sided driving, we have to check whether we can enter the
+        // roundabout later in the cycle, rather than prior.
+        if (!edge_data.roundabout && node_based_graph.GetTarget(road.turn.eid) != from_nid &&
+            past_roundabout_angle)
+        {
+            road.entry_allowed = false;
+        }
+    }
+}
+
 bool RoundaboutHandler::isRotary(const NodeID nid) const
 {
     // translate a node ID into its respective coordinate stored in the node_info_list
@@ -191,7 +228,6 @@ Intersection RoundaboutHandler::handleRoundabouts(const bool is_rotary,
                                                   const bool can_exit_roundabout_separately,
                                                   Intersection intersection) const
 {
-    // TODO requires differentiation between roundabouts and rotaries
     // detect via radius (get via circle through three vertices)
     NodeID node_v = node_based_graph.GetTarget(via_eid);
     if (on_roundabout)