#ifndef _BvHierarchy_H__
#define _BvHierarchy_H__

#include <stack>

#include "Mesh.h"
#include "Containers.h"
#include "Statistics.h"
#include "VssRay.h"
#include "RayInfo.h"
#include "gzstream.h"
#include "SubdivisionCandidate.h"
#include "AxisAlignedBox3.h"
#include "IntersectableWrapper.h"


namespace GtpVisibilityPreprocessor {


class ViewCellLeaf;
class Plane3;
class AxisAlignedBox3;
class Ray;
class ViewCellsStatistics;
class ViewCellsManager;
class MergeCandidate;
class Beam;
class ViewCellsTree;
class Environment;
class BvhInterior;
class BvhLeaf;
class BvhNode;
class BvhIntersectable;
class BvhTree;
class VspTree;
class ViewCellsContainer;
//class BvhSubdivisionCandidate;


/** View space partition statistics.
*/
class BvhStatistics: public StatisticsBase
{
public:
	// total number of nodes
	int nodes;
	// number of splits
	int splits;
	// maximal reached depth
	int maxDepth;
	// minimal depth
	int minDepth;
	// max depth nodes
	int maxDepthNodes;
	// minimum depth nodes
	int minDepthNodes;
	// nodes with minimum objects
	int minObjectsNodes;
	// minimum area nodes
	int minProbabilityNodes;
	/// nodes termination because of max cost ratio;
	int maxCostNodes;
	// max number of rays per node
	int maxObjectRefs;
	/// number of invalid leaves
	int invalidLeaves;
	/// accumulated number of rays refs
	//int accumRays;
	// accumulated depth (used to compute average)
	int accumDepth;
	/// object references
	int objectRefs;

	// Constructor
	BvhStatistics() 
	{
		Reset();
	}

	int Nodes() const {return nodes;}
	int Interior() const { return nodes / 2; }
	int Leaves() const { return (nodes / 2) + 1; }
	
	// TODO: computation wrong
	double AvgDepth() const 
	{ return accumDepth / (double)Leaves(); } 

	void Reset() 
	{
		nodes = 0;
		splits = 0;
		
		maxDepth = 0;
		minDepth = 99999;
		accumDepth = 0;
       	maxDepthNodes = 0;
		minObjectsNodes = 0;
		minProbabilityNodes = 0;
		maxCostNodes = 0;
		invalidLeaves = 0;
		maxObjectRefs = 0;
		objectRefs = 0;
	}

	void Print(ostream &app) const;

	friend ostream &operator<<(ostream &s, const BvhStatistics &stat) 
	{
		stat.Print(s);
		return s;
	} 
};


/**
    VspNode abstract class serving for interior and leaf node implementation
*/
class BvhNode
{
public:
	
	// types of vsp nodes
	enum {Interior, Leaf};

	BvhNode();
	BvhNode(const AxisAlignedBox3 &bbox);
	BvhNode(const AxisAlignedBox3 &bbox, BvhInterior *parent);

	virtual ~BvhNode(){};

	/** Determines whether this node is a leaf or not
		@return true if leaf
	*/
	virtual bool IsLeaf() const = 0;

	/** Determines whether this node is a root
		@return true if root
	*/
	virtual bool IsRoot() const;

	/** Returns parent node.
	*/
	BvhInterior *GetParent();

	/** Sets parent node.
	*/
	void SetParent(BvhInterior *parent);

	/** The bounding box specifies the node extent.
	*/
	AxisAlignedBox3 GetBoundingBox() const
	{ return mBoundingBox; }


	void SetBoundingBox(const AxisAlignedBox3 &boundingBox) 
	{ mBoundingBox = boundingBox; }


	/////////////////////////////////////
	//-- mailing options
	
	static void NewMail(const int reserve = 1) {
		sMailId += sReservedMailboxes;
		sReservedMailboxes = reserve;
	}
	
	void Mail() { mMailbox = sMailId; }
	bool Mailed() const { return mMailbox == sMailId; }

	void Mail(const int mailbox) { mMailbox = sMailId + mailbox; }
	bool Mailed(const int mailbox) const { return mMailbox == sMailId + mailbox; }

	int IncMail() { return ++ mMailbox - sMailId; }

	static int sMailId;
	int mMailbox;
	static int sReservedMailboxes;

	///////////////////////////////////

protected:
	
	/// the bounding box of the node
	AxisAlignedBox3 mBoundingBox;
	/// parent of this node
	BvhInterior *mParent;
};


/** BSP interior node implementation 
*/
class BvhInterior: public BvhNode 
{
public:
	/** Standard contructor taking a bounding box as argument.
	*/
	BvhInterior(const AxisAlignedBox3 &bbox);
	BvhInterior(const AxisAlignedBox3 &bbox, BvhInterior *parent);

	~BvhInterior();
	/** @return false since it is an interior node 
	*/
	bool IsLeaf() const;
	
	BvhNode *GetBack() { return mBack; }
	BvhNode *GetFront() { return mFront; }

	/** Replace front or back child with new child.
	*/
	void ReplaceChildLink(BvhNode *oldChild, BvhNode *newChild);

	/** Replace front and back child.
	*/
	void SetupChildLinks(BvhNode *front, BvhNode *back);

	friend ostream &operator<<(ostream &s, const BvhInterior &A)
	{
		return s << A.mBoundingBox;
	}

protected:

	/// back node
	BvhNode *mBack;
	/// front node
	BvhNode *mFront;
};


/** BSP leaf node implementation.
*/
class BvhLeaf: public BvhNode 
{
public:
	/** Standard contructor taking a bounding box as argument.
	*/
	BvhLeaf(const AxisAlignedBox3 &bbox);
	BvhLeaf(const AxisAlignedBox3 &bbox, BvhInterior *parent);
	BvhLeaf(const AxisAlignedBox3 &bbox, BvhInterior *parent, const int numObjects);

	~BvhLeaf();

	/** @return true since it is an interior node 
	*/
	bool IsLeaf() const;
	
	SubdivisionCandidate *GetSubdivisionCandidate()// const
	{ 
		return mSubdivisionCandidate; 
	}

	void SetSubdivisionCandidate(SubdivisionCandidate *candidate)
	{ 
		mSubdivisionCandidate = candidate; 
	}

public:

	/// Rays piercing this leaf.
	VssRayContainer mVssRays;
	/// objects
	ObjectContainer mObjects;
	/// universal counter
	int mCounter;

protected:

	/// pointer to a split plane candidate splitting this leaf
	SubdivisionCandidate *mSubdivisionCandidate;
};


typedef map<BvhNode *, BvhIntersectable *> BvhIntersectableMap;


/** View Space Partitioning tree.
*/
class BvHierarchy 
{
	friend class ViewCellsParseHandlers;
	friend class HierarchyManager;

public:
	
	/** Additional data which is passed down the BSP tree during traversal.
	*/
	class BvhTraversalData
	{  
	public:
		
		BvhTraversalData():
		mNode(NULL),
		mDepth(0),
		mProbability(0.0),
		mMaxCostMisses(0), 
		mPriority(0),
		mAxis(0)
		{}
		
		BvhTraversalData(BvhLeaf *node, 
						 const int depth,
						 const AxisAlignedBox3 &box,
						 const float v):
		mNode(node), 
		mDepth(depth),
		mBoundingBox(box),
		mProbability(v),
		mMaxCostMisses(0),
		mPriority(0),
		mAxis(0)
		{}


		/** Returns cost of the traversal data.
		*/
		float GetCost() const
		{
			return mPriority;
		}

		/// deletes contents and sets them to NULL
		void Clear()
		{
			DEL_PTR(mNode);
		}

		/// the current node
		BvhLeaf *mNode;
		/// current depth
		int mDepth;
		/// the probability that this node is seen
		float mProbability;
		/// the bounding box of the node
		AxisAlignedBox3 mBoundingBox;
		/// how often this branch has missed the max-cost ratio
		int mMaxCostMisses;
		/// current axis
		int mAxis;
		/// current priority
		float mPriority;


		friend bool operator<(const BvhTraversalData &a, const BvhTraversalData &b)
		{
			return a.GetCost() < b.GetCost();
		}
    };

	/** Candidate for a view space split.
	*/
	class BvhSubdivisionCandidate: public SubdivisionCandidate
	{  
	public:

        BvhSubdivisionCandidate(const BvhTraversalData &tData): mParentData(tData)
		{};

		~BvhSubdivisionCandidate() 
		{ 
			mParentData.Clear(); 
		}

		int Type() const { return OBJECT_SPACE; }
	
		void EvalPriority()
		{
			sBvHierarchy->EvalSubdivisionCandidate(*this);	
		}

		bool GlobalTerminationCriteriaMet() const
		{
			return sBvHierarchy->GlobalTerminationCriteriaMet(mParentData);
		}

		BvhSubdivisionCandidate(
			const ObjectContainer &frontObjects, 
			const ObjectContainer &backObjects, 
			const BvhTraversalData &tData): 
		mFrontObjects(frontObjects), mBackObjects(backObjects), mParentData(tData)
		{}

		/// pointer to parent tree.
		static BvHierarchy *sBvHierarchy;
		/// parent data
		BvhTraversalData mParentData;
		/// the objects on the front of the potential split
		ObjectContainer mFrontObjects;
		/// the objects on the back of the potential split
		ObjectContainer mBackObjects;
	};

	/** Struct for traversing line segment.
	*/
	struct LineTraversalData 
	{
		BvhNode *mNode;
		Vector3 mExitPoint;
		
		float mMaxT;
    
		LineTraversalData () {}
		LineTraversalData (BvhNode *n, const Vector3 &p, const float maxt):
		mNode(n), mExitPoint(p), mMaxT(maxt) {}
	};


	/** Default constructor creating an empty tree.
	*/ 
	BvHierarchy();

	/** Default destructor.
	*/
	~BvHierarchy();

	/** Returns tree statistics.
	*/
	const BvhStatistics &GetStatistics() const; 
  
	/** Returns bounding box of the specified node.
	*/
	AxisAlignedBox3 GetBoundingBox(BvhNode *node) const;

	/** Reads parameters from environment singleton.
	*/
	void ReadEnvironment();

	/** Evaluates candidate for splitting.
	*/
	void EvalSubdivisionCandidate(BvhSubdivisionCandidate &splitData);

	/** Returns list of leaves with pvs smaller than
		a certain threshold.
		@param onlyUnmailed if only the unmailed leaves should be considered
		@param maxPvs the maximal pvs of a leaf to be added (-1 means unlimited)
	*/
	void CollectLeaves(vector<BvhLeaf *> &leaves) const;

	/** Returns bounding box of the whole tree (= bbox of root node)
	*/
	AxisAlignedBox3 GetBoundingBox()const;

	/** Returns root of the view space partitioning tree.
	*/
	BvhNode *GetRoot() const;

	/** A ray is cast possible intersecting the tree.
		@param the ray that is cast.
		@returns the number of intersections with objects stored in the tree.
	*/
	//int CastRay(Ray &ray);

	/** finds neighbouring leaves of this tree node.
	*/
	int FindNeighbors(BvhLeaf *n, 
					  vector<BvhLeaf *> &neighbors, 
					  const bool onlyUnmailed) const;

	/** Returns random leaf of BSP tree.
		@param halfspace defines the halfspace from which the leaf is taken.
	*/
	BvhLeaf *GetRandomLeaf(const Plane3 &halfspace);

	/** Returns random leaf of BSP tree.
		@param onlyUnmailed if only unmailed leaves should be returned.
	*/
	BvhLeaf *GetRandomLeaf(const bool onlyUnmailed = false);

	/** Casts line segment into the tree.
		@param origin the origin of the line segment
		@param termination the end point of the line segment
		@returns view cells intersecting the line segment.
	*/
    int CastLineSegment(const Vector3 &origin,
						const Vector3 &termination,
						ViewCellContainer &viewcells);
		
	/** Sets pointer to view cells manager.
	*/
	void SetViewCellsManager(ViewCellsManager *vcm);

	/** Writes tree to output stream
	*/
	bool Export(OUT_STREAM &stream);

	/** Returns or creates a new intersectable for use in a kd based pvs.
		The OspTree is responsible for destruction of the intersectable.
	*/
	BvhIntersectable *GetOrCreateBvhIntersectable(BvhNode *node);

	/** Collects rays.
	*/
	void CollectRays(const ObjectContainer &objects, VssRayContainer &rays) const;

	/** Intersects box with the tree and returns the number of intersected boxes.
		@returns number of view cells found
	*/
	int ComputeBoxIntersections(
		const AxisAlignedBox3 &box, 
		ViewCellContainer &viewCells) const;


	/** Returns leaf the point pt lies in, starting from root.
	*/
	BvhLeaf *GetLeaf(Intersectable *obj, BvhNode *root = NULL) const;

	ViewCellsTree *GetViewCellsTree() const { return mViewCellsTree; }
	
	void SetViewCellsTree(ViewCellsTree *vt) { mViewCellsTree = vt; }

	/** Add the bvh leaf to the pvs of the view cell.
	*/
	bool AddLeafToPvs(
		BvhLeaf *leaf, 
		ViewCell *vc, 
		const float pdf, 
		float &contribution);

protected:

	/** Returns true if tree can be terminated.
	*/
	bool LocalTerminationCriteriaMet(const BvhTraversalData &data) const;

	/** Returns true if global tree can be terminated.
	*/
	bool GlobalTerminationCriteriaMet(const BvhTraversalData &data) const;

	/** For sorting the objects during the heuristics
	*/
	struct SortableEntry
	{
		Intersectable *mObject;
		float mPos;

		SortableEntry() {}

		SortableEntry(Intersectable *obj, const float pos): 
		mObject(obj), mPos(pos)
		{}

		bool operator<(const SortableEntry &b) const 
		{
			return mPos < b.mPos;
		}
	};
 
	/** Evaluate balanced object partition.
	*/
	float EvalLocalObjectPartition(
		const BvhTraversalData &tData,
		const int axis,
		ObjectContainer &objectsFront,
		ObjectContainer &objectsBack);

	float EvalSah(
		const BvhTraversalData &tData,
		const int axis,
		ObjectContainer &objectsFront,
		ObjectContainer &objectsBack);

	/** Computes priority of the traversal data and stores it in tData.
	*/
	void EvalPriority(BvhTraversalData &tData) const;

	/** Evaluates render cost of next split.
	*/
	float EvalRenderCost(
		const BvhTraversalData &tData,
		const ObjectContainer &objectsLeft,
		const ObjectContainer &objectsRight) const;

	/** Evaluates tree stats in the BSP tree leafs.
	*/
	void EvaluateLeafStats(const BvhTraversalData &data);

	/** Subdivides node using a best split priority queue.
	    @param tQueue the best split priority queue
		@param splitCandidate the candidate for the next split
		@param globalCriteriaMet if the global termination criteria were already met
		@returns new root of the subtree
	*/
	BvhNode *Subdivide(
		SplitQueue &tQueue, 
		SubdivisionCandidate *splitCandidate,
		const bool globalCriteriaMet);
	
	/** Subdivides leaf.
		@param leaf the leaf to be subdivided
		
		@param polys the polygons to be split
		@param frontPolys returns the polygons in front of the split plane
		@param backPolys returns the polygons in the back of the split plane
		
		@param rays the polygons to be filtered
		@param frontRays returns the polygons in front of the split plane
		@param backRays returns the polygons in the back of the split plane

		@returns the root of the subdivision
	*/
	BvhInterior *SubdivideNode(
		const ObjectContainer &frontObjects,
		const ObjectContainer &backObjects,
		const BvhTraversalData &tData,
		BvhTraversalData &frontData,
		BvhTraversalData &backData);

	/** Splits the objects for the next subdivision.
		@returns cost for this split
	*/
	float SelectObjectPartition(
		const BvhTraversalData &tData,
		ObjectContainer &frontObjects,
		ObjectContainer &backObjects);
	
	/** Writes the node to disk
		@note: should be implemented as visitor.
	*/
	void ExportNode(BvhNode *node, OUT_STREAM &stream);

	void ExportObjects(BvhLeaf *leaf, OUT_STREAM &stream);

	/** Returns estimated memory usage of tree.
	*/
	float GetMemUsage() const;

	/** Creates new root of hierarchy.
	*/
	void CreateRoot(const ObjectContainer &objects);

	/////////////////////////////
	// Helper functions for local cost heuristics

	
	/** Sorts split candidates for cost heuristics using axis aligned splits.
		@param node the current node
		@param axis the current split axis
	*/
	void SortSubdivisionCandidates(
		const BvhTraversalData &data,
		const int axis);

	/** Computes best cost for axis aligned planes.
	*/
	float EvalLocalCostHeuristics(
		const BvhTraversalData &tData,
		const int axis,
		ObjectContainer &objectsFront,
		ObjectContainer &objectsFBack);

	/** Evaluates the contribution to the front and back volume
		when this object is changing sides in the bvs.

		@param object the object
		@param volLeft updates the left pvs
		@param volPvs updates the right pvs
	*/
	void EvalHeuristicsContribution(
		Intersectable *obj,
		float &volLeft, 
		float &volRight);

	/** Prepares objects for the cost heuristics.
		@returns sum of volume of associated view cells
	*/
	float PrepareHeuristics(const BvhTraversalData &tData, const int axis);
	

	////////////////////////////////////////////////


	/** Prepares construction for vsp and osp trees.
	*/
	AxisAlignedBox3 ComputeBoundingBox(
		const ObjectContainer &objects, 
		const AxisAlignedBox3 *parentBox = NULL);

	void CollectDirtyCandidates(
		BvhSubdivisionCandidate *sc,
		vector<SubdivisionCandidate *> &dirtyList);

	/** Collect view cells which see this bvh leaf.
	*/
	void CollectViewCells(
		const ObjectContainer &objects, 
		ViewCellContainer &viewCells,
		const bool setCounter = false) const;

	/** Collects view cells which see an object.
	*/
	void CollectViewCells(
		Intersectable *object, 
		ViewCellContainer &viewCells, 
		const bool useMailBoxing,
		const bool setCounter = false) const;

	/** Rays will be clipped to the bounding box.
	*/
	void PreprocessRays(
		BvhLeaf *root, 
		const VssRayContainer &sampleRays,
		RayInfoContainer &rays);

	/** Print the subdivision stats in the subdivison log.
	*/
	void PrintSubdivisionStats(const SubdivisionCandidate &tData);

	void AddSubdivisionStats(
		const int viewCells,
		const float renderCostDecr,
		const float totalRenderCost);

	void AssociateObjectsWithRays(const VssRayContainer &rays);

	bool IsObjectInLeaf(BvhLeaf *, Intersectable *object) const;

	SubdivisionCandidate *PrepareConstruction(
		const VssRayContainer &sampleRays,
		const ObjectContainer &objects
		);

	float EvalViewCellsVolume(const ObjectContainer &objects) const;


protected:
	
	/// pointer to the hierarchy of view cells
	ViewCellsTree *mViewCellsTree;

	VspTree *mVspTree;

	/// The view cells manager
	ViewCellsManager *mViewCellsManager;

	/// candidates for placing split planes during cost heuristics
	vector<SortableEntry> *mSubdivisionCandidates;

	/// Pointer to the root of the tree
	BvhNode *mRoot;
		
	/// Statistics for the object space partition
	BvhStatistics mBvhStats;
	
	/// box around the whole view domain
	AxisAlignedBox3 mBoundingBox;


	//-- local termination

	/// maximal possible depth
	int mTermMaxDepth;
	/// mininum probability
	float mTermMinProbability;
	/// minimal number of objects
	int mTermMinObjects;
	/// maximal contribution per ray
	float mTermMaxRayContribution;
	/// maximal acceptable cost ratio
	float mTermMaxCostRatio;
	/// tolerance value indicating how often the max cost ratio can be failed
	int mTermMissTolerance;


	//-- global criteria

	float mTermMinGlobalCostRatio;
	int mTermGlobalCostMissTolerance;
	int mGlobalCostMisses;

	/// maximal number of view cells
	int mTermMaxLeaves;
	/// maximal tree memory
	float mMaxMemory;
	/// the tree is out of memory
	bool mOutOfMemory;


	//-- split heuristics based parameters
	
	bool mUseCostHeuristics;
	/// balancing factor for PVS criterium
	float mCtDivCi;	
	/// if only driving axis should be used for split
	bool mOnlyDrivingAxis;
	
	/// current time stamp (used for keeping split history)
	int mTimeStamp;
	// if rays should be stored in leaves
	bool mStoreRays;

	/// epsilon for geometric comparisons
	float mEpsilon;

	/// subdivision stats output file
	ofstream  mSubdivisionStats;
	/// keeps track of cost during subdivision
	float mTotalCost;
	/// keeps track of overall pvs size during subdivision
	int mTotalPvsSize;
	/// number of currenly generated view cells
	int mCreatedLeaves;

	/// represents min and max band for sweep
	float mSplitBorder;

	/// weight between render cost decrease and node render cost
	float mRenderCostDecreaseWeight;

	/// stores the kd node intersectables used for pvs
	BvhIntersectableMap mBvhIntersectables;

};

}

#endif