/*
 * Copyright (c) 2011-2019, The DART development contributors
 * All rights reserved.
 *
 * The list of contributors can be found at:
 *   https://github.com/dartsim/dart/blob/master/LICENSE
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 *   without modification, are permitted provided that the following
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 *   * Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *   * Redistributions in binary form must reproduce the above
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 */

#ifndef DART_CONSTRAINT_CONSTRAINTBASE_HPP_
#define DART_CONSTRAINT_CONSTRAINTBASE_HPP_

#include <cstddef>

#include "dart/dynamics/SmartPointer.hpp"

namespace dart {

namespace dynamics {
class Skeleton;
}  // namespace dynamics

namespace constraint {

/// ConstraintInfo
struct ConstraintInfo
{
  /// Impulse
  double* x;

  /// Lower bound of x
  double* lo;

  /// Upper bound of x
  double* hi;

  /// Bias term
  double* b;

  /// Slack variable
  double* w;

  /// Friction index
  int* findex;

  /// Inverse of time step
  double invTimeStep;
};

/// Constraint is a base class of concrete constraints classes
class ConstraintBase
{
public:
  /// Return dimesion of this constranit
  std::size_t getDimension() const;

  /// Update constraint using updated Skeleton's states
  virtual void update() = 0;

  /// Fill LCP variables
  virtual void getInformation(ConstraintInfo* info) = 0;

  /// Apply unit impulse to constraint space
  virtual void applyUnitImpulse(std::size_t index) = 0;

  /// Get velocity change due to the uint impulse
  virtual void getVelocityChange(double* vel, bool withCfm) = 0;

  /// Excite the constraint
  virtual void excite() = 0;

  /// Unexcite the constraint
  virtual void unexcite() = 0;

  /// Apply computed constraint impulse to constrained skeletons
  virtual void applyImpulse(double* lambda) = 0;

  /// Return true if this constraint is active
  virtual bool isActive() const = 0;

  ///
  virtual dynamics::SkeletonPtr getRootSkeleton() const = 0;

  ///
  virtual void uniteSkeletons();

  ///
  static dynamics::SkeletonPtr compressPath(dynamics::SkeletonPtr skeleton);

  ///
  static dynamics::SkeletonPtr getRootSkeleton(dynamics::SkeletonPtr skeleton);

  //----------------------------------------------------------------------------
  // Friendship
  //----------------------------------------------------------------------------

  friend class ConstraintSolver;
  friend class ConstrainedGroup;

  /// Destructor
  virtual ~ConstraintBase();

protected:
  /// Default contructor
  ConstraintBase();

protected:
  /// Dimension of constraint
  std::size_t mDim;
};

} // namespace constraint
} // namespace dart

#endif  // DART_CONSTRAINT_CONSTRAINTBASE_HPP_

