New cpp folder structure

Signed-off-by: Alexander Borsuk <me@alex.bio>

libs/routing/position_accumulator.hpp

@@ -0,0 +1,43 @@
+#pragma once
+
+#include "geometry/point2d.hpp"
+
+#include <queue>
+
+namespace routing
+{
+/// \brief This class accumulates a track of some number of last gps positions.
+/// The track is used to calculate the direction of an end user.
+class PositionAccumulator
+{
+public:
+  // Several last gps positions are accumulating in |PositionAccumulator::m_points|.
+  // The last position (the last point from |m_points|) may be removed if after the removing it
+  // the length of the all track will be more than |kMinTrackLengthM|.
+  static double constexpr kMinTrackLengthM = 70.0;
+
+  // All segments which are shorter than |kMinValidSegmentLengthM| are not added to the track.
+  static double constexpr kMinValidSegmentLengthM = 10.0;
+
+  // If a segment is longer then |kMaxValidSegmentLengthM|
+  // all the content of |m_points| is removed and the current point is added to track.
+  static double constexpr kMaxValidSegmentLengthM = 80.0;
+
+  void PushNextPoint(m2::PointD const & point);
+  void Clear();
+
+  /// \returns direction or {0.0, 0.0} if |m_points| is empty or contains only one item.
+  m2::PointD GetDirection() const;
+
+  // Getters for testing this class.
+  std::deque<m2::PointD> const & GetPointsForTesting() const { return m_points; }
+  double GetTrackLengthMForTesting() const { return m_trackLengthM; }
+
+private:
+  // There's the current position at the end. At the beginning there's the last position of the track.
+  // The distance between them is more or equal than |kMinTrackLengthM| if there're enough points in
+  // |m_points|.
+  std::deque<m2::PointD> m_points;
+  double m_trackLengthM = 0.0;
+};
+}  // routing