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#ifndef ActorTree_INCLUDE_ONCE
#define ActorTree_INCLUDE_ONCE

#include <vlGraphics/Actor.hpp>
#include <vlCore/AABB.hpp>
#include <set>

namespace vl
{
  /** The ActorTreeAbstract class implements the interface of a generic tree containing Actors in its nodes.
   *
   * The interface of ActorTreeAbstract allows you to:
   * - Modify the Actors contained in each node
   * - Traverse the tree and visit its nodes
   * - Compute the AABB of a single node or of the whole tree
   *
   * Does \b not allow you to:
   * - Add new nodes to the tree
   *
   * \sa
   * - ActorKdTree
   * - ActorTree
   */
  class VLGRAPHICS_EXPORT ActorTreeAbstract: public Object
  {
    VL_INSTRUMENT_ABSTRACT_CLASS(vl::ActorTreeAbstract, Object)

  public:
    ActorTreeAbstract();

    //! Returns the number of child nodes of an ActorTreeAbstract node.
    virtual int childrenCount() const = 0;
    //! Returns the i-th child node of an ActorTreeAbstract node.
    virtual ActorTreeAbstract* child(int i) = 0;
    //! Returns the i-th child node of an ActorTreeAbstract node.
    virtual const ActorTreeAbstract* child(int i) const = 0;

    //! Returns the parent of a node.
    const ActorTreeAbstract* parent() const { return mParent; }
    //! Returns the parent of a node.
    ActorTreeAbstract* parent() { return mParent; }

    //! Returns the actors contained in a ActorTree node
    const ActorCollection* actors() const { return &mActors; }
    //! Returns the actors contained in a ActorTree node
    ActorCollection* actors() { return &mActors; }

    //! Returns the bounding box of a node. Such bounding box contains both the bounding boxes of the node's Actors and of the child nodes.
    const AABB& aabb() const { return mAABB; }

    //! Recursively computes the bounding box of a node so that it includes the bounding boxes of the node's Actors and of the child nodes.
    void computeAABB();

    /**
     * Extracts all the Actors contained in th ActorTree hierarchy and appends them to the given ActorCollection.
     * This ignores the Actors isEnabled() and enableMask() and the ActorTreeAbstract::isEnabled() flag as well.
     */
    void extractActors(ActorCollection& list);

    /**
     * Extracts the enabled and visible Actors contained in th ActorTree hierarchy and appends them to the given ActorCollection.
     * This function implements a hierarchycal frustum culling algorithm that culls the nodes of the bounding box tree first and then
     * the single Actors contained in the nodes that could not be culled.
     * If `camera` is NULL no frustum culling is performed.
     * This function alwasy take into consideration the Actors isEnabled() and enableMask() and the ActorTreeAbstract::isEnabled() flag as well.
     * \see SceneManager::enableMask(), Actor::enableMask(), Actor::isEnabled(), ActorTreeAbstract::isEnabled()
     */
    void extractVisibleActors(ActorCollection& list, const Camera* camera, unsigned enable_mask=0xFFFFFFFF);

    /**
     * Removes the given Actor from the ActorTreeAbstract.
     */
    ActorTreeAbstract* eraseActor(Actor* actor);

    //! Utility function that adds an Actor and binds it to the given Renderable, Effect and Transform.
    Actor* addActor(Renderable* renderable, Effect* eff, Transform* tr=NULL);

    //! Utility function equivalent to 'actors()->push_back(actor)'.
    Actor* addActor(Actor* actor);

    /**
     * Updates the Transform and the bounds of the given Actors.
     * Before you create a bounding box tree or a kd-tree of Actors you have to
     * make sure that their Transform and bounding volumes are up-to-date. This
     * is an utility function that lets you do that in a simple an quick way.
     */
    static void prepareActors(ActorCollection& actors);

    //! For internal use only.
    void setParent(ActorTreeAbstract* p) { mParent = p; }

    //! If `false` then extractVisibleActors() will ignore this node and all its children.
    //! \see Actor::enableMask(), Actor::isEnabled(), ActorTreeAbstract::isEnabled(), SceneManager::enableMask(), Rendering::enableMask(), Rendering::effectOverrideMask(), Renderer::enableMask(), Renderer::shaderOverrideMask().
    void setEnabled( bool enabled ) { mEnabled = enabled; }

    //! If `false` then extractVisibleActors() will ignore this node and all its children.
    //! \see Actor::enableMask(), Actor::isEnabled(), ActorTreeAbstract::isEnabled(), SceneManager::enableMask(), Rendering::enableMask(), Rendering::effectOverrideMask(), Renderer::enableMask(), Renderer::shaderOverrideMask().
    bool isEnabled() const { return mEnabled; }

  protected:
    ActorTreeAbstract* mParent;
    ActorCollection mActors;
    AABB mAABB;
    bool mEnabled;
  };
}

#endif