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#ifndef DART_CONSTRAINT_WELDJOINTCONSTRAINT_HPP_
#define DART_CONSTRAINT_WELDJOINTCONSTRAINT_HPP_

#include <Eigen/Dense>

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

namespace dart {
namespace constraint {

/// WeldJointConstraint represents weld joint constraint between a body and the
/// world or between two bodies
class WeldJointConstraint : public JointConstraint
{
public:
  /// Constructor that takes one body
  explicit WeldJointConstraint(dynamics::BodyNode* _body);

  /// Constructor that takes two bodies
  WeldJointConstraint(dynamics::BodyNode* _body1, dynamics::BodyNode* _body2);

  /// Set the relative transform that this WeldJointConstraint will enforce
  void setRelativeTransform(const Eigen::Isometry3d& _tf);

  /// Get the relative transform that this WeldJointConstraint will enforce
  const Eigen::Isometry3d& getRelativeTransform() const;

  /// Destructor
  virtual ~WeldJointConstraint();

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:
  ///
  Eigen::Isometry3d mRelativeTransform;

  ///
  Eigen::Vector6d mViolation;

  ///
  const Eigen::Matrix6d mJacobian1;

  ///
  Eigen::Matrix6d mJacobian2;

  ///
  double mOldX[6];

  /// 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_WELDJOINTCONSTRAINT_HPP_
