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#ifndef DART_CONSTRAINT_BALLJOINTCONSTRAINT_HPP_
#define DART_CONSTRAINT_BALLJOINTCONSTRAINT_HPP_

#include <Eigen/Dense>

#include "dart/math/MathTypes.hpp"
#include "dart/constraint/JointConstraint.hpp"

namespace dart {
namespace constraint {

/// BallJointConstraint represents ball joint constraint between a body and the
/// world or between two bodies
class BallJointConstraint : public JointConstraint
{
public:
  /// Constructor that takes one body and the joint position in the world frame
  /// \param[in] _body
  /// \param[in] _jointPos Joint position expressed in world frame
  BallJointConstraint(dynamics::BodyNode* _body,
                      const Eigen::Vector3d& _jointPos);


  /// Constructor that takes two bodies and the joint position in the frame of
  /// _body1
  /// \param[in] _body1
  /// \param[in] _body2
  /// \param[in] _jointPos Joint position expressed in world frame
  BallJointConstraint(dynamics::BodyNode* _body1, dynamics::BodyNode* _body2,
                      const Eigen::Vector3d& _jointPos);

  /// Destructor
  virtual ~BallJointConstraint();

protected:
  //----------------------------------------------------------------------------
  // Constraint virtual functions
  //----------------------------------------------------------------------------

  // Documentation inherited
  void update() override;

  // Documentation inherited
  void getInformation(ConstraintInfo* _lcp) override;

  // Documentation inherited
  void applyUnitImpulse(std::size_t _index) override;

  // Documentation inherited
  void getVelocityChange(double* _vel, bool _withCfm) override;

  // Documentation inherited
  void excite() override;

  // Documentation inherited
  void unexcite() override;

  // Documentation inherited
  void applyImpulse(double* _lambda) override;

  // Documentation inherited
  bool isActive() const override;

  // Documentation inherited
  dynamics::SkeletonPtr getRootSkeleton() const override;

  // Documentation inherited
  void uniteSkeletons() override;

private:
  /// Offset from the origin of body frame 1 to the ball joint position where
  /// the offset is expressed in body frame 1
  Eigen::Vector3d mOffset1;

  /// Offset from the origin of body frame 2 to the ball joint position where
  /// the offset is expressed in body frame 2
  Eigen::Vector3d mOffset2;

  /// Position constraint violation expressed in body frame 1
  Eigen::Vector3d mViolation;

  /// Linear map between constraint space and Cartesian space for body1
  Eigen::Matrix<double, 3, 6> mJacobian1;

  /// Linear map between constraint space and Cartesian space for body2
  Eigen::Matrix<double, 3, 6> mJacobian2;

  ///
  double mOldX[3];

  /// Index of applied impulse
  std::size_t mAppliedImpulseIndex;

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

}  // namespace constraint
}  // namespace dart

#endif  // DART_CONSTRAINT_BALLJOINTCONSTRAINT_HPP_

