#ifndef _OcclusionCullingSceneManager_H__
#define _OcclusionCullingSceneManager_H__

#include "OgreSceneNode.h"
#include "OgreSceneManager.h"
#include "OgrePrerequisites.h"
#include "OgreSolidHalfBoundingBox.h"
#include <queue>

using namespace std;

namespace Ogre {
	/**
		This class implements the compare operator for the priority queue.
		a lower distance has a higher value in the queue
	*/
	template <typename T> class myless
	{
	public:
		myless(Camera *cam) { mCamera = cam; }
		//bool operator() (HierarchyNode *v1, HierarchyNode *v2) const
		bool operator() (T v1, T v2) const
		{
			return v1->getSquaredViewDepth(mCamera) > v2->getSquaredViewDepth(mCamera);
		}
	private:
		Camera *mCamera;
	};

	typedef pair<SceneNode *, HardwareOcclusionQuery *> query_pair;
	typedef priority_queue<SceneNode *, vector<SceneNode *>, myless<vector<SceneNode *>::value_type> > PriorityQueue;
	typedef queue<query_pair> QueryQueue;
	/**
		Class which implements a scene mangager which uses occlusion queries for culling occluded objects
	*/
	class OcclusionCullingSceneManager : public SceneManager
	{
	public:
		OcclusionCullingSceneManager();
		~OcclusionCullingSceneManager();
	

		enum {RENDER_CULL_FRUSTUM, RENDER_STOP_AND_WAIT, RENDER_COHERENT, NUM_RENDERMODES};
		
		/** Overriden from SceneManager. Renders the scene with the specified algorithm
		/**
			The algorithm is one of
			RENDER_CULL_FRUSTUM: renders the scene with view frustum culling only
			RENDER_STOP_AND_WAIT: renders the scene with the hierarchical stop and wait algorithm
			RENDER_COHERENT: renders the scene with the coherent hierarchical algorithm
		*/
		void _renderVisibleObjects(void);
		void _findVisibleObjects(Camera* cam, bool onlyShadowCasters);
		void _updateSceneGraph(Camera* cam);

	protected:
		enum {MODE_QUERY, MODE_RENDER};

		int isLeaf(SceneNode *node);
		int countSceneNodes(SceneNode *node);
		void renderZPass();
		void traverseNode(SceneNode *node);
		/** Renders current node */
		void render(SceneNode *node);
		/** Sets rendering mode, e.g. query mode or render mode*/
		void setRenderingMode(int mode);
		
		/** Renders the scene with view frustum culling only. */
		void renderCullFrustum();
		/** Renders the scene with the hierarchical stop and wait algorithm. */
		void renderStopAndWait();
		/** Renders the scene with the coherent hierarchical algorithm and the query queye. */
		void renderCoherentWithQueue();
		/** Issue a occlusion query for this node. */
		HardwareOcclusionQuery *issueOcclusionQuery(SceneNode *node, bool wasVisible);
		/** Pulls up the visibility from the child nodes. */
		void pullUpVisibility(SceneNode *node);
		/** delete all previously defined occlusion queries */
		void deleteQueries();
		/** Renders bounding box of specified node.
		@param the node which bounding box is to be rendered
		*/
		void renderBoundingBox(SceneNode *node);
		/** Returns one half of the bounding box.
		@param the half of the bouding box
		*/
		SolidHalfBoundingBox *getSolidHalfBoundingBox(int half);
		/** sets the type of the algorithm
		@param algorithm type
		*/
		void setAlgorithmType(int type);
	
		int getAlgorithmType();

		// we use a priority queue rather than a renderstack
		PriorityQueue *mDistanceQueue; 
		
		unsigned int mFrameId;
		unsigned int mVisibilityThreshold;
		unsigned int mNumSceneNodes;
		int mCurrentTestIdx;
		int mQueryMode;
		
		std::vector<HardwareOcclusionQuery *> mOcclusionQueries;
		// two halfes of a aabb
		SolidHalfBoundingBox *mHalfBoundingBox[2];	
		int mAlgorithmType;
	};

}
#endif // OCCLUSIONCULLINGSCENEMANAGER_H