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#ifndef DART_DYNAMICS_BALLJOINT_HPP_
#define DART_DYNAMICS_BALLJOINT_HPP_

#include <Eigen/Dense>

#include "dart/dynamics/GenericJoint.hpp"

namespace dart {
namespace dynamics {

/// class BallJoint
class BallJoint : public GenericJoint<math::SO3Space>
{
public:
  friend class Skeleton;

  using Base = GenericJoint<math::SO3Space>;

  struct Properties : Base::Properties
  {
    DART_DEFINE_ALIGNED_SHARED_OBJECT_CREATOR(Properties)

    Properties(const Base::Properties& properties = Base::Properties());

    virtual ~Properties() = default;
  };

  /// Destructor
  virtual ~BallJoint();

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

  /// Get joint type for this class
  static const std::string& getStaticType();

  // Documentation inherited
  bool isCyclic(std::size_t _index) const override;

  /// Get the Properties of this BallJoint
  Properties getBallJointProperties() const;

  /// Convert a rotation into a 3D vector that can be used to set the positions
  /// of a BallJoint. The positions returned by this function will result in a
  /// relative transform of
  /// getTransformFromParentBodyNode() * _rotation *
  /// getTransformFromChildBodyNode().inverse() between the parent BodyNode and
  /// the child BodyNode frames when applied to a BallJoint.
  template <typename RotationType>
  static Eigen::Vector3d convertToPositions(const RotationType& _rotation)
  {
    return math::logMap(_rotation);
  }

  /// Convert a BallJoint-style position vector into a transform
  static Eigen::Isometry3d convertToTransform(
      const Eigen::Vector3d& _positions);

  /// Convert a BallJoint-style position vector into a rotation matrix
  static Eigen::Matrix3d convertToRotation(const Eigen::Vector3d& _positions);

  // Documentation inherited
  Eigen::Matrix<double, 6, 3> getRelativeJacobianStatic(
      const Eigen::Vector3d& _positions) const override;

  // Documentation inherited
  Eigen::Vector3d getPositionDifferencesStatic(
      const Eigen::Vector3d& _q2, const Eigen::Vector3d& _q1) const override;

protected:
  /// Constructor called by Skeleton class
  BallJoint(const Properties& properties);

  // Documentation inherited
  Joint* clone() const override;

  using Base::getRelativeJacobianStatic;

  // Documentation inherited
  void integratePositions(double _dt) override;

  // Documentation inherited
  void updateDegreeOfFreedomNames() override;

  // Documentation inherited
  void updateRelativeTransform() const override;

  // Documentation inherited
  void updateRelativeJacobian(bool _mandatory = true) const override;

  // Documentation inherited
  void updateRelativeJacobianTimeDeriv() const override;

protected:
  /// Access mR, which is an auto-updating variable
  const Eigen::Isometry3d& getR() const;

  /// Rotation matrix dependent on the generalized coordinates
  ///
  /// Do not use directly! Use getR() to access this
  mutable Eigen::Isometry3d mR;

public:
  // To get byte-aligned Eigen vectors
  EIGEN_MAKE_ALIGNED_OPERATOR_NEW
};

} // namespace dynamics
} // namespace dart

#endif // DART_DYNAMICS_BALLJOINT_HPP_
