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#ifndef DART_DYNAMICS_LINESEGMENTSHAPE_HPP_
#define DART_DYNAMICS_LINESEGMENTSHAPE_HPP_

#include "dart/dynamics/Shape.hpp"

namespace dart {
namespace dynamics {

/// The LineSegmentShape facilitates creating graphs of line segments. The graph
/// can consist of a single line segment or many interconnected line segments.
/// Note: LineSegmentShape may NOT be used as a collision shape for BodyNodes,
/// but it may be used for visualization purposes.
class LineSegmentShape : public Shape
{
public:
  /// Default constructor
  LineSegmentShape(float _thickness = 1.0f);

  /// Constructor for creating a simple line segment that connects two vertices
  LineSegmentShape(
      const Eigen::Vector3d& _v1,
      const Eigen::Vector3d& _v2,
      float _thickness = 1.0f);

  // Documentation inherited.
  const std::string& getType() const override;

  /// Returns shape type for this class
  static const std::string& getStaticType();

  /// Set the line thickness/width for rendering
  void setThickness(float _thickness);

  /// Get the line thickness/width used for rendering
  float getThickness() const;

  /// Add a vertex as a child to the last vertex that was added
  std::size_t addVertex(const Eigen::Vector3d& _v);

  /// Add a vertex as a child to the specified vertex
  std::size_t addVertex(const Eigen::Vector3d& _v, std::size_t _parent);

  /// Remove a vertex from the list of vertices. IMPORTANT: Note that this
  /// alters the indices of all vertices that follow it in the list, which also
  /// clobbers the validity of the list of connections for all those vertices.
  /// A safer and more efficient method might be to recycle vertices by moving
  /// them around with setVertex() and/or altering their connections.
  void removeVertex(std::size_t _idx);

  /// Change the location of the specified vertex
  void setVertex(std::size_t _idx, const Eigen::Vector3d& _v);

  /// Get the location of the specified vertex. Returns a zero vector if an
  /// out-of-bounds vertex is requested.
  const Eigen::Vector3d& getVertex(std::size_t _idx) const;

  /// Get all the vertices
  const std::vector<Eigen::Vector3d>& getVertices() const;

  /// Create a connection between the two specified vertices
  void addConnection(std::size_t _idx1, std::size_t _idx2);

  /// Search for a connection between two vertices and break it if it exists.
  /// This is less efficient but more robust than removeConnection(std::size_t).
  void removeConnection(std::size_t _vertexIdx1, std::size_t _vertexIdx2);

  /// Remove the specified connection entry. Note that this will impact the
  /// indices of all connections that come after _connectionIdx. This is more
  /// efficient but less robust than removeConnection(std::size_t,std::size_t)
  void removeConnection(std::size_t _connectionIdx);

  /// Get all the connections
  const common::aligned_vector<Eigen::Vector2i>& getConnections() const;

  /// The returned inertia matrix will be like a very thin cylinder. The _mass
  /// will be evenly distributed across all lines.
  Eigen::Matrix3d computeInertia(double mass) const override;

  // TODO(MXG): Consider supporting colors-per-vertex

protected:
  // Documentation inherited.
  void updateBoundingBox() const override;

  // Documentation inherited
  void updateVolume() const override;

  /// Line thickness for rendering
  float mThickness;

  /// Vector of vertices
  std::vector<Eigen::Vector3d> mVertices;

  /// Vector of connections
  common::aligned_vector<Eigen::Vector2i> mConnections;

  /// A dummy vertex that can be returned when an out-of-bounds vertex is
  /// requested
  static const Eigen::Vector3d mDummyVertex;
};

} // namespace dynamics
} // namespace dart

#endif // DART_DYNAMICS_LINESEGMENTSHAPE_HPP_
