#ifndef PHYSICSCOLLISIONOBJECT_H_
#define PHYSICSCOLLISIONOBJECT_H_

#include "Vector3.h"
#include "PhysicsCollisionShape.h"

namespace gameplay
{

class Node;
class PhysicsRigidBody;
class PhysicsCharacter;
class PhysicsGhostObject;
class PhysicsVehicle;
class PhysicsVehicleWheel;

/**
 * Base class for all gameplay physics objects that support collision events.
 */
class PhysicsCollisionObject
{
    friend class PhysicsController;
    friend class PhysicsConstraint;
    friend class PhysicsRigidBody;
    friend class PhysicsGhostObject;

public:

    /**
     * Represents the different types of collision objects.
     */
    enum Type
    {
        /**
         * PhysicsRigidBody type.
         */
        RIGID_BODY,

        /**
         * PhysicsCharacter type.
         */
        CHARACTER,

        /** 
         * PhysicsGhostObject type.
         */
        GHOST_OBJECT,

        /** 
         * PhysicsVehicle type.
         */
        VEHICLE,

        /** 
         * PhysicsVehicleWheel type.
         */
        VEHICLE_WHEEL,

        /**
         * No collision object.
         */
        NONE
    };

    /** 
     * Defines a pair of rigid bodies that collided (or may collide).
     */
    class CollisionPair
    {
    public:

        /**
         * Constructor.
         */
        CollisionPair(PhysicsCollisionObject* objectA, PhysicsCollisionObject* objectB);

        /**
         * Less than operator (needed for use as a key in map).
         * 
         * @param collisionPair The collision pair to compare.
         * @return True if this pair is "less than" the given pair; false otherwise.
         */
        bool operator < (const CollisionPair& collisionPair) const;

        /**
         * The first object in the collision.
         */
        PhysicsCollisionObject* objectA;

        /**
         * The second object in the collision.
         */
        PhysicsCollisionObject* objectB;
    };

    /**
     * Collision listener interface.
     */
    class CollisionListener
    {
        friend class PhysicsCollisionObject;
        friend class PhysicsController;

    public:

        /**
         * The type of collision event.
         */
        enum EventType
        {
            /**
             * Event fired when the two rigid bodies start colliding.
             */
            COLLIDING,

            /**
             * Event fired when the two rigid bodies no longer collide.
             */
            NOT_COLLIDING
        };

        /**
         * Virtual destructor.
         */
        virtual ~CollisionListener() { }

        /**
         * Called when a collision occurs between two objects in the physics world.
         * 
         * NOTE: You are not permitted to disable physics objects from within this callback. Disabling physics on a collision object
         *  removes the object from the physics world. This is not permitted during the PhysicsController::update.
         *
         * @param type The type of collision event.
         * @param collisionPair The two collision objects involved in the collision.
         * @param contactPointA The contact point with the first object (in world space).
         * @param contactPointB The contact point with the second object (in world space).
         */
        virtual void collisionEvent(PhysicsCollisionObject::CollisionListener::EventType type,
                                    const PhysicsCollisionObject::CollisionPair& collisionPair,
                                    const Vector3& contactPointA = Vector3::zero(),
                                    const Vector3& contactPointB = Vector3::zero()) = 0;
    };

    /**
     * Virtual destructor.
     */
    virtual ~PhysicsCollisionObject();

    /**
     * Returns the type of the collision object.
     */
    virtual PhysicsCollisionObject::Type getType() const = 0;

    /**
     * Returns the type of the shape for this collision object.
     */
    PhysicsCollisionShape::Type getShapeType() const;

    /**
     * Returns the node associated with this collision object.
     */
    Node* getNode() const;

    /**
     * Returns the collision shape.
     *
     * @return The collision shape.
     */
    PhysicsCollisionShape* getCollisionShape() const;

    /**
     * Returns whether this collision object is kinematic.
     *
     * A kinematic collision object is an object that is not simulated by
     * the physics system and instead has its transform driven manually.
     *
     * @return true if the collision object is kinematic.
     */
    bool isKinematic() const;

    /**
     * Returns whether this collision object is dynamic.
     *
     * A dynamic collision object is simulated entirely by the physics system,
     * such as with dynamic rigid bodies. 
     *
     * @return true if the collision object is dynamic.
     */
    bool isDynamic() const;

    /**
     * Check if the collision object is enabled.
     *
     * @return true if the collision object is enabled.
     */
    bool isEnabled() const;

    /**
     * Sets the collision object to be enabled or disabled.
     *
     * @param enable true enables the collision object, false disables it.
     */
    void setEnabled(bool enable);

    /**
     * Adds a collision listener for this collision object.
     * 
     * @param listener The listener to add.
     * @param object Optional collision object used to filter the collision event.
     */
    void addCollisionListener(CollisionListener* listener, PhysicsCollisionObject* object = NULL);

    /**
     * Removes a collision listener.
     *
     * @param listener The listener to remove.
     * @param object Optional collision object used to filter the collision event.
     */
    void removeCollisionListener(CollisionListener* listener, PhysicsCollisionObject* object = NULL);

    /**
     * Adds a collision listener for this collision object.
     * 
     * Note: the given Lua function must match the function signature of PhysicsCollisionObject::CollisionListener::collisionEvent.
     * 
     * @param function The Lua script function to add as a listener callback.
     * @param object Optional collision object used to filter the collision event.
     */
    void addCollisionListener(const char* function, PhysicsCollisionObject* object = NULL);

    /**
     * Removes a collision listener.
     *
     * @param function The Lua function (used as a listener callback) to remove.
     * @param object Optional collision object used to filter the collision event.
     */
    void removeCollisionListener(const char* function, PhysicsCollisionObject* object = NULL);

    /**
     * Checks if this collision object collides with the given object.
     * 
     * @param object The collision object to test for collision with.
     * 
     * @return true if this object collides with the specified one; false otherwise.
     */
    bool collidesWith(PhysicsCollisionObject* object) const;

    /**
     * Returns this collision object as a physics rigid body.
     *
     * If this collision object is not of type RIGID_BODY, this method returns NULL.
     *
     * @return This collision object cast to a PhysicsRigidBody.
     */
    PhysicsRigidBody* asRigidBody();

    /**
     * Returns this collision object as a physics character.
     *
     * If this collision object is not of type CHARACTER, this method returns NULL.
     *
     * @return This collision object cast to a PhysicsCharacter.
     */
    PhysicsCharacter* asCharacter();

    /**
     * Returns this collision object as a physics ghost object.
     *
     * If this collision object is not of type GHOST_OBJECT, this method returns NULL.
     *
     * @return This collision object cast to a PhysicsGhostObject.
     */
    PhysicsGhostObject* asGhostObject();

    /**
     * Returns this collision object as a physics vehicle.
     *
     * If this collision object is not of type VEHICLE, this method returns NULL.
     *
     * @return This collision object cast to a PhysicsVehicle.
     */
    PhysicsVehicle* asVehicle();

    /**
     * Returns this collision object as a physics vehicle wheel.
     *
     * If this collision object is not of type VEHICLE_WHEEL, this method returns NULL.
     *
     * @return This collision object cast to a PhysicsVehicleWheel.
     */
    PhysicsVehicleWheel* asVehicleWheel();

protected:

    /**
     * Handles collision event callbacks to Lua script functions.
     */
    struct ScriptListener : public CollisionListener
    {
        /**
         * Constructor.
         */
        ScriptListener(const char* url);

        /**
         * @see PhysicsCollisionObject::CollisionListener
         */
        void collisionEvent(PhysicsCollisionObject::CollisionListener::EventType type, const PhysicsCollisionObject::CollisionPair& collisionPair,
                                    const Vector3& contactPointA, const Vector3& contactPointB);

        /** The URL to the Lua script function to use as the callback. */
        std::string url;
        /** The name of the Lua script function to use as the callback. */
        std::string function;
    };

    /**
     * Constructor.
     */
    PhysicsCollisionObject(Node* node);

    /**
     * Returns the Bullet Physics collision object.
     *
     * @return The Bullet collision object.
     */
    virtual btCollisionObject* getCollisionObject() const = 0;

    /**
     * Pointer to Node contained by this collision object.
     */ 
    Node* _node;
    
    /**
     * The PhysicsCollisionObject's collision shape.
     */
    PhysicsCollisionShape* _collisionShape;

    /**
     * If the collision object is enabled or not.
     */
    bool _enabled;

    /**
     * The list of script listeners.
     */
    std::vector<ScriptListener*>* _scriptListeners;

private:

    /**
     * Interface between GamePlay and Bullet to keep object transforms synchronized properly.
     * 
     * @see btMotionState
     */
    class PhysicsMotionState : public btMotionState
    {
        friend class PhysicsConstraint;
        
    public:
        
        /**
         * Creates a physics motion state for a rigid body.
         * 
         * @param node The node that contains the transformation to be associated with the motion state.
         * @param collisionObject The collision object that owns the motion state.
         * @param centerOfMassOffset The translation offset to the center of mass of the rigid body.
         */
        PhysicsMotionState(Node* node, PhysicsCollisionObject* collisionObject, const Vector3* centerOfMassOffset = NULL);
        
        /**
         * Destructor.
         */
        virtual ~PhysicsMotionState();
        
        /**
         * @see btMotionState::getWorldTransform
         */
        virtual void getWorldTransform(btTransform &transform) const;
        
        /**
         * @see btMotionState::setWorldTransform
         */
        virtual void setWorldTransform(const btTransform &transform);
        
        /**
         * Updates the motion state's world transform from the GamePlay Node object's world transform.
         */
        void updateTransformFromNode() const;
        
        /**
         * Sets the center of mass offset for the associated collision shape.
         */
        void setCenterOfMassOffset(const Vector3& centerOfMassOffset);
        
    private:
        
        Node* _node;
        PhysicsCollisionObject* _collisionObject;
        btTransform _centerOfMassOffset;
        mutable btTransform _worldTransform;
    };

    /** 
     * The PhysicsCollisionObject's motion state.
     */
    PhysicsMotionState* _motionState;
};

}

#endif
