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#ifndef DART_UTILS_MJCF_DETAIL_INERTIAL_HPP_
#define DART_UTILS_MJCF_DETAIL_INERTIAL_HPP_

#include <tinyxml2.h>

#include "dart/common/Optional.hpp"
#include "dart/math/MathTypes.hpp"
#include "dart/utils/mjcf/detail/Compiler.hpp"
#include "dart/utils/mjcf/detail/Error.hpp"

namespace dart {
namespace utils {
namespace MjcfParser {
namespace detail {

class Body;

class Inertial final
{
public:
  Inertial() = default;

  Errors read(tinyxml2::XMLElement* element);

  void setMass(double mass);
  double getMass() const;

  void setDiagInertia(const Eigen::Vector3d& inertia);
  const Eigen::Vector3d& getDiagInertia() const;

  void setOffDiagInertia(const Eigen::Vector3d& inertia);
  const Eigen::Vector3d& getOffDiagInertia() const;

  void setRelativeTransform(const Eigen::Isometry3d& tf);
  const Eigen::Isometry3d& getRelativeTransform() const;

  void setWorldTransform(const Eigen::Isometry3d& tf);
  const Eigen::Isometry3d& getWorldTransform() const;

private:
  // Private members used by Body class
  friend class Body;
  Errors compile(const Compiler& compiler);

private:
  struct Data
  {
    /// Position of the inertial frame.
    Eigen::Vector3d mPos{Eigen::Vector3d::Zero()};

    /// Quaternion
    Eigen::Quaterniond mQuat{Eigen::Quaterniond::Identity()};

    /// These are the quantities (x, y, z, a) mentioned above. The last number
    /// is the angle of rotation, in degrees or radians as specified by the
    /// angle attribute of compiler.
    std::optional<Eigen::Vector4d> mAxisAngle;

    /// Rotation angles around three coordinate axes.
    std::optional<Eigen::Vector3d> mEuler;

    /// The first 3 numbers are the X axis of the frame. The next 3 numbers are
    /// the Y axis of the frame, which is automatically made orthogonal to the X
    /// axis. The Z axis is then defined as the cross-product of the X and Y
    /// axes.
    std::optional<Eigen::Vector6d> mXYAxes;

    /// The Z axis of the frame
    std::optional<Eigen::Vector3d> mZAxis;

    Eigen::Isometry3d mRelativeTransform{Eigen::Isometry3d::Identity()};
    Eigen::Isometry3d mWorldTransform{Eigen::Isometry3d::Identity()};

    /// Mass of the body.
    double mMass{0};

    /// Diagonal inertia matrix, expressing the body inertia relative to the
    /// inertial frame.
    std::optional<Eigen::Vector3d> mDiagInertia;

    /// Full inertia matrix M.
    std::optional<Eigen::Vector6d> mFullInertia;
  };

  Data mData;

  /// Position of the inertial frame.
  Eigen::Vector3d mPos{Eigen::Vector3d::Zero()};

  Eigen::Isometry3d mRelativeTransform{Eigen::Isometry3d::Identity()};
  Eigen::Isometry3d mWorldTransform{Eigen::Isometry3d::Identity()};

  /// Mass of the body.
  double mMass{0};

  Eigen::Vector3d mDiagonalInertia{Eigen::Vector3d::Zero()};
  Eigen::Vector3d mOffDiagonalInertia{Eigen::Vector3d::Zero()};
};

} // namespace detail
} // namespace MjcfParser
} // namespace utils
} // namespace dart

#endif // #ifndef DART_UTILS_MJCF_DETAIL_INERTIAL_HPP_
