/********************************************************************************
* ReactPhysics3D physics library, http://www.reactphysics3d.com                 *
* Copyright (c) 2010-2016 Daniel Chappuis                                       *
*********************************************************************************
*                                                                               *
* This software is provided 'as-is', without any express or implied warranty.   *
* In no event will the authors be held liable for any damages arising from the  *
* use of this software.                                                         *
*                                                                               *
* Permission is granted to anyone to use this software for any purpose,         *
* including commercial applications, and to alter it and redistribute it        *
* freely, subject to the following restrictions:                                *
*                                                                               *
* 1. The origin of this software must not be misrepresented; you must not claim *
*    that you wrote the original software. If you use this software in a        *
*    product, an acknowledgment in the product documentation would be           *
*    appreciated but is not required.                                           *
*                                                                               *
* 2. Altered source versions must be plainly marked as such, and must not be    *
*    misrepresented as being the original software.                             *
*                                                                               *
* 3. This notice may not be removed or altered from any source distribution.    *
*                                                                               *
********************************************************************************/

#ifndef REACTPHYSICS3D_CONSTRAINT_H
#define REACTPHYSICS3D_CONSTRAINT_H

// Libraries
#include "configuration.h"
#include "body/RigidBody.h"
#include "mathematics/mathematics.h"

// ReactPhysics3D namespace
namespace reactphysics3d {

/// Enumeration for the type of a constraint
enum class JointType {BALLSOCKETJOINT, SLIDERJOINT, HINGEJOINT, FIXEDJOINT};

// Class declarations
struct ConstraintSolverData;
class Joint;

// Structure JointListElement
/**
 * This structure represents a single element of a linked list of joints
 */
struct JointListElement {

    public:

        // -------------------- Attributes -------------------- //

        /// Pointer to the actual joint
        Joint* joint;

        /// Next element of the list
        JointListElement* next;

        // -------------------- Methods -------------------- //

        /// Constructor
        JointListElement(Joint* initJoint, JointListElement* initNext)
                        :joint(initJoint), next(initNext){

        }
};

// Structure JointInfo
/**
 * This structure is used to gather the information needed to create a joint.
 */
struct JointInfo {

    public :

        // -------------------- Attributes -------------------- //

        /// First rigid body of the joint
        RigidBody* body1;

        /// Second rigid body of the joint
        RigidBody* body2;

        /// Type of the joint
        JointType type;

        /// Position correction technique used for the constraint (used for joints).
        /// By default, the BAUMGARTE technique is used
        JointsPositionCorrectionTechnique positionCorrectionTechnique;

        /// True if the two bodies of the joint are allowed to collide with each other
        bool isCollisionEnabled;

        /// Constructor
        JointInfo(JointType constraintType)
                      : body1(nullptr), body2(nullptr), type(constraintType),
                        positionCorrectionTechnique(JointsPositionCorrectionTechnique::NON_LINEAR_GAUSS_SEIDEL),
                        isCollisionEnabled(true) {}

        /// Constructor
        JointInfo(RigidBody* rigidBody1, RigidBody* rigidBody2, JointType constraintType)
                      : body1(rigidBody1), body2(rigidBody2), type(constraintType),
                        positionCorrectionTechnique(JointsPositionCorrectionTechnique::NON_LINEAR_GAUSS_SEIDEL),
                        isCollisionEnabled(true) {
        }

        /// Destructor
        virtual ~JointInfo() = default;

};

// Class Joint
/**
 * This abstract class represents a joint between two bodies.
 */
class Joint {

    protected :

        // -------------------- Attributes -------------------- //

        /// Pointer to the first body of the joint
        RigidBody* const mBody1;

        /// Pointer to the second body of the joint
        RigidBody* const mBody2;

        /// Type of the joint
        const JointType mType;

        /// Body 1 index in the velocity array to solve the constraint
        uint mIndexBody1;

        /// Body 2 index in the velocity array to solve the constraint
        uint mIndexBody2;

        /// Position correction technique used for the constraint (used for joints)
        JointsPositionCorrectionTechnique mPositionCorrectionTechnique;

        /// True if the two bodies of the constraint are allowed to collide with each other
        bool mIsCollisionEnabled;

        /// True if the joint has already been added into an island
        bool mIsAlreadyInIsland;

        // -------------------- Methods -------------------- //

        /// Return true if the joint has already been added into an island
        bool isAlreadyInIsland() const;

        /// Return the number of bytes used by the joint
        virtual size_t getSizeInBytes() const = 0;

        /// Initialize before solving the joint
        virtual void initBeforeSolve(const ConstraintSolverData& constraintSolverData) = 0;

        /// Warm start the joint (apply the previous impulse at the beginning of the step)
        virtual void warmstart(const ConstraintSolverData& constraintSolverData) = 0;

        /// Solve the velocity constraint
        virtual void solveVelocityConstraint(const ConstraintSolverData& constraintSolverData) = 0;

        /// Solve the position constraint
        virtual void solvePositionConstraint(const ConstraintSolverData& constraintSolverData) = 0;

    public :

        // -------------------- Methods -------------------- //

        /// Constructor
        Joint(const JointInfo& jointInfo);

        /// Destructor
        virtual ~Joint() = default;

        /// Deleted copy-constructor
        Joint(const Joint& constraint) = delete;

        /// Deleted assignment operator
        Joint& operator=(const Joint& constraint) = delete;

        /// Return the reference to the body 1
        RigidBody* getBody1() const;

        /// Return the reference to the body 2
        RigidBody* getBody2() const;

        /// Return true if the constraint is active
        bool isActive() const;

        /// Return the type of the constraint
        JointType getType() const;

        /// Return true if the collision between the two bodies of the joint is enabled
        bool isCollisionEnabled() const;

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

        friend class DynamicsWorld;
        friend class Island;
        friend class ConstraintSolver;
};

// Return the reference to the body 1
/**
 * @return The first body involved in the joint
 */
inline RigidBody* Joint::getBody1() const {
    return mBody1;
}

// Return the reference to the body 2
/**
 * @return The second body involved in the joint
 */
inline RigidBody* Joint::getBody2() const {
    return mBody2;
}

// Return true if the joint is active
/**
 * @return True if the joint is active
 */
inline bool Joint::isActive() const {
    return (mBody1->isActive() && mBody2->isActive());
}

// Return the type of the joint
/**
 * @return The type of the joint
 */
inline JointType Joint::getType() const {
    return mType;
}

// Return true if the collision between the two bodies of the joint is enabled
/**
 * @return True if the collision is enabled between the two bodies of the joint
 *              is enabled and false otherwise
 */
inline bool Joint::isCollisionEnabled() const {
    return mIsCollisionEnabled;
}

// Return true if the joint has already been added into an island
inline bool Joint::isAlreadyInIsland() const {
    return mIsAlreadyInIsland;
}

}

#endif