basic turn lane handling

include/extractor/guidance/turn_discovery.hpp

@@ -0,0 +1,38 @@
+#ifndef OSRM_EXTRACTOR_GUIDANCE_TURN_DISCOVERY_HPP_
+#define OSRM_EXTRACTOR_GUIDANCE_TURN_DISCOVERY_HPP_
+
+#include "extractor/guidance/intersection.hpp"
+#include "extractor/guidance/turn_analysis.hpp"
+#include "util/typedefs.hpp"
+
+#include <string>
+
+namespace osrm
+{
+namespace extractor
+{
+namespace guidance
+{
+namespace lanes
+{
+
+// OSRM processes edges by looking at a via_edge, coming into an intersection. For turn lanes, we
+// might require to actually look back a turn. We do so in the hope that the turn lanes match up at
+// the previous intersection for all incoming lanes.
+bool findPreviousIntersection(
+    const NodeID node,
+    const EdgeID via_edge,
+    const Intersection intersection,
+    const TurnAnalysis &turn_analysis,                   // to generate other intersections
+    const util::NodeBasedDynamicGraph &node_based_graph, // query edge data
+    // output parameters, will be in an arbitrary state on failure
+    NodeID &result_node,
+    EdgeID &result_via_edge,
+    Intersection &result_intersection);
+
+} // namespace lanes
+} // namespace guidance
+} // namespace extractor
+} // namespace osrm
+
+#endif /*OSRM_EXTRACTOR_GUIDANCE_TURN_DISCOVERY_HPP_*/