// A class representing any in-game object.
// TODO: (?) add "drawIn(SomeKindOfGraphicsContext)" method.
// TODO: (?) add "getCollisionMesh()" method.
class Entity
{
public:

    // Apply a transformation (translation + rotation) in a 2D coordinatable.
    // TODO: (?) add "bool applyRotation = true" parameter.
    virtual void applyTransformIn(EntityCoordinatable2D * c2d) const = 0;

    // Apply a translation in a 2D coordinatable.
    // TODO: (?) deprecate, replace by "applyTransformIn(c2d, false)".
    virtual void applyTranslateIn(EntityCoordinatable2D * c2d) const = 0;

    // Get the current coordinate of this entity. Might be calculated if there
    // is a movement active.
    virtual const EntityCoordinate2D getCoordinate() const = 0;

    // Get the dimension of this entity.
    virtual EntityDimension2D getDimension() const = 0;

    // Get the current orientation of this entity. Might be calculated if there
    // is an angular motion active.
    virtual const EntityTheta1D getOrientation() const = 0;

    // Increment the time of this entity by milliseconds.
    virtual void incrementTime(unsigned int time) = 0;

    // Get whether this entity is solid and should be checked for collisions
    // with other entities non-solid entities.
    // TODO: (?) Deprecate. Replace by "getCollisionMesh()".
    virtual const bool isSolid() const = 0;

    // Draw this entity using the current OpenGL context. Transform is not
    // applied prior to drawing. Use "applyTransformIn(GLCoordinatable2D)" to
    // apply transform to the GL context prior to drawing the entity.
    // TODO: (?) Deprecate, replace by "drawIn(SomeKindOfGraphicsContext)".
    virtual void drawInGL() const = 0;

    // Deconstructor
    virtual ~Entity(){};
};

// A class representing a movable ingame object.
class MovableEntity: public Entity
{
private:

    // The last known determined coordinate of this entity before the start of
    // any kind of applicable motion. Coordination is measured in points.
    EntityCoordinate2D coordinate;

    // The last known determined orientation of this entity before the start of
    // ant kind of applicable motion. Orientation is measured in radians.
    EntityTheta1D orientation;

    // The current velocity of the entity. The angle is relative to the angle
    // of the entity, which is relative to the world. Speed is measured in
    // points per second. Rotation is measured in radians per second.
    EntityVelocity2D velocity;

    // The current speed of the angular movement, in radians per second.
    EntityTheta1D angularSpeed;

    // The motion-duration of the current velocity and rotation in milliseconds.
    EntityTime motionDuration;

private:

    // A method to apply the new coordinate and orientation based on the current
    // active motion (velocity and angular speed) and motion duration.
    // properties "coordinate" and "orientation" will be updated and property
    // "motionDuration" will be reset to 0.
    // This method doesn't affect the "velocity" and "angularSpeed" properties.
    void applyMotion();

protected:

    // Construct a new entity based on a coordinate and an orientation.
    MovableEntity(EntityCoordinate2D coordinate = EntityCoordinate2D(0,0),
                  EntityTheta1D orientation = EntityTheta1D(0));

    // Set the velocity of this entity. The actual velocity applied might be
    // differend due the max speed in the requested direction of this entity.
    void setVelocity(EntityVelocity2D velocity);

    // Set the angular speed of this entity. The actual speed applied might
    // be differend due the max angular speed of this entity.
    void setAngularSpeed(EntityTheta1D speed);

    // Get the maximum speed of this entity in a certain direction.
    virtual EntityCoordinate1D getMaxSpeedInDirection(EntityTheta1D theta) = 0;

    // Get the maxmimum angular speed of this entity.
    virtual EntityTheta1D getMaxAngularSpeed() = 0;

public:

    // Get the current coordinate of this entity. Might be calculated if there
    // is a movement active.
    virtual const EntityCoordinate2D getCoordinate() const;

    // Get the current orientation of this entity. Might be calculated if there
    // is an angular motion active.
    virtual const EntityTheta1D getOrientation() const;

    // Increment the time of this entity by milliseconds.
    virtual void incrementTime(unsigned int time);

    // Get the speed of the angular motion of this entity.
    inline const EntityTheta1D getAngularSpeed() const
    {return this->angularSpeed;}

    // Get the velocity of this entity.
    inline const EntityVelocity2D getVelocity() const
    {return this->velocity;}

    // Apply a transformation (translation + rotation) in a 2D coordinatable.
    virtual void applyTransformIn(EntityCoordinatable2D * c2d) const;

    // Apply a translation in a 2D coordinatable.
    virtual void applyTranslateIn(EntityCoordinatable2D * c2d) const;

    // Deconstructor
    virtual ~MovableEntity(){};
};


// A class representing a "smart" movable entity which could control itself
// based on controller input.
// TODO: add methods to receive paths from a path-finder.
class Unit: public MovableEntity
{
private:

    // The health of this unit.
    Health health;

protected:

    // Increment (or Decrement) the health of this unit. Actual applied
    // increment might be differend due the maximum health limit of this unit.
    inline void incrementHealth(int increment)
    {this->setHealth(this->health+increment);}

    // Set the health of this unit. The actual health applied might be differend
    // due the maximum health limit of this unit.
    inline void setHealth(Health health)
    {this->health = between<Health>(health, 0, this->getMaxHealth());}

public:

    // Get the max health of this unit.
    virtual Health getMaxHealth() const = 0;

    // Get the owner of this unit, or NULL if this unit is un-owned (neutral).
    // TODO: Create "Owner" class and update return-type.
    virtual void * getOwner() const = 0;

    // Get the health of this unit.
    inline Health getHealth()
    {return this->health;}
};