#ifndef _VspBspTree_H__
#define _VspBspTree_H__

#include "Mesh.h"
#include "Containers.h"
#include "Polygon3.h"
#include <stack>
#include "Statistics.h"
#include "VssRay.h"
#include "RayInfo.h"

class ViewCell;
class BspViewCell;
class Plane3;
class VspBspTree;  
class VspBspInterior;
class VspBspNode;
class AxisAlignedBox3;
class Ray;

class VspBspNodeGeometry
{
public:
	VspBspNodeGeometry()
	{};  

	~VspBspNodeGeometry();

	float GetArea() const;
	
	/** Computes new cell based on the old cell definition and a new split plane
		@param side indicates which side of the halfspace 
	*/
	void SplitGeometry(VspBspNodeGeometry &front, 
					   VspBspNodeGeometry &back,
					   const VspBspTree &tree,
					   const Plane3 &splitPlane) const;

	Polygon3 *SplitPolygon(Polygon3 *poly, const VspBspTree &tree) const;

	PolygonContainer mPolys;
};

/** Data structure used for optimized ray casting.
*/
struct VspBspRayTraversalData 
{
    VspBspNode *mNode;
    Vector3 mExitPoint;
    float mMaxT;
    
    VspBspRayTraversalData() {}

    VspBspRayTraversalData(VspBspNode *n, const Vector3 &extp, const float maxt):
    mNode(n), mExitPoint(extp), mMaxT(maxt) 
	{}
};

class VspBspTreeStatistics: public StatisticsBase
{
public:
	// total number of nodes
	int nodes;
	// number of splits
	int splits;
	// totals number of rays
	int rays;
	// maximal reached depth
	int maxDepth;
	// minimal depth
	int minDepth;
	
	// max depth nodes
	int maxDepthNodes;
	// minimum depth nodes
	int minDepthNodes;
	// max depth nodes
	int minPvsNodes;
	// nodes with minimum PVS
	int minRaysNodes;
	// max ray contribution nodes
	int maxRayContribNodes;
	// minimum area nodes
	int minAreaNodes;

	// max number of rays per node
	int maxObjectRefs;
	// accumulated depth (used to compute average)
	int accumDepth;
	// number of initial polygons
	int polys;
	/// samples contributing to pvs
	int contributingSamples;
	/// sample contributions to pvs
	int sampleContributions;
	/// largest pvs
	int largestPvs;

	// Constructor
	VspBspTreeStatistics() 
	{
		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;
		polys = 0;
		accumDepth = 0;
        
		maxDepthNodes = 0;
		minPvsNodes = 0;
		minRaysNodes = 0;
		maxRayContribNodes = 0;
		minAreaNodes = 0;

		contributingSamples = 0;
		sampleContributions = 0;
	}

	void Print(ostream &app) const;

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

class VspBspViewCellsStatistics: public StatisticsBase
{
public:

	/// number of view cells
	int viewCells;

	/// size of the PVS
	int pvs;
  
	/// largest PVS of all view cells
	int maxPvs;

	/// smallest PVS of all view cells
	int minPvs;

	/// view cells with empty PVS
	int emptyPvs;

	/// number of bsp leaves covering the view space
	int bspLeaves;

	/// largest number of leaves covered by one view cell  
	int maxVspBspLeaves;

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

	double AvgVspBspLeaves() const {return (double)bspLeaves / (double)viewCells;};
	double AvgPvs() const {return (double)pvs / (double)viewCells;};
  
	void Reset() 
	{
		viewCells = 0;	
		pvs = 0;  
		maxPvs = 0;

		minPvs = 999999;
		emptyPvs = 0;
		bspLeaves = 0;
		maxVspBspLeaves = 0;
	}

	void Print(ostream &app) const;

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

/**
    VspBspNode abstract class serving for interior and leaf node implementation
*/
class VspBspNode 
{
	friend class VspBspTree;

public:
	VspBspNode();
	virtual ~VspBspNode(){};
	VspBspNode(VspBspInterior *parent);

	/** 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.
	*/
	VspBspInterior *GetParent();

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

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

protected:

	/// parent of this node
	VspBspInterior *mParent;
};

/** BSP interior node implementation 
*/
class VspBspInterior : public VspBspNode 
{
	friend class VspBspTree;
public:
	/** Standard contructor taking split plane as argument.
	*/
	VspBspInterior(const Plane3 &plane);
	~VspBspInterior();
	/** @return false since it is an interior node 
	*/
	bool IsLeaf() const;

	VspBspNode *GetBack();
	VspBspNode *GetFront();

	Plane3 *GetPlane();

	void ReplaceChildLink(VspBspNode *oldChild, VspBspNode *newChild);
	void SetupChildLinks(VspBspNode *b, VspBspNode *f);

	/** Splits polygons with respect to the split plane.
		@param polys the polygons to be split. the polygons are consumed and
			   distributed to the containers frontPolys, backPolys, coincident.
		@param frontPolys returns the polygons in the front of the split plane
		@param backPolys returns the polygons in the back of the split plane
		@param coincident returns the polygons coincident to the split plane

		@returns the number of splits	
	*/
	int SplitPolygons(PolygonContainer &polys, 
					  PolygonContainer &frontPolys, 
					  PolygonContainer &backPolys, 
					  PolygonContainer &coincident);

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

protected:

	/// Splitting plane corresponding to this node
	Plane3 mPlane;
	/// back node
	VspBspNode *mBack;
	/// front node
	VspBspNode *mFront;
};

/** BSP leaf node implementation.
*/
class VspBspLeaf : public VspBspNode 
{
	friend class VspBspTree;

public:
	VspBspLeaf();
	VspBspLeaf(BspViewCell *viewCell);
	VspBspLeaf(VspBspInterior *parent);
	VspBspLeaf(VspBspInterior *parent, BspViewCell *viewCell);

	/** @return true since it is an interior node 
	*/
	bool IsLeaf() const;
	
	/** Returns pointer of view cell.
	*/
	BspViewCell *GetViewCell() const;

	/** Sets pointer to view cell.
	*/
	void SetViewCell(BspViewCell *viewCell);

	/** Adds ray sample contributions to the PVS.
		@param sampleContributions the number contributions of the samples
		@param contributingSampels the number of contributing rays
		
	*/
	void AddToPvs(const RayInfoContainer &rays, 
				  int &sampleContributions,
				  int &contributingSamples, 
				  bool storeLeavesWithRays = false);

protected:

	/// if NULL this does not correspond to feasible viewcell
	BspViewCell *mViewCell;
};

/** Implementation of the view cell BSP tree. 
*/
class VspBspTree 
{
public:
	
	/** Additional data which is passed down the BSP tree during traversal.
	*/
	struct VspBspTraversalData
	{  
		/// the current node
		VspBspNode *mNode;
		/// polygonal data for splitting
		PolygonContainer *mPolygons;
		/// current depth
		int mDepth;
		/// the view cell associated with this subdivsion
		ViewCell *mViewCell;
		/// rays piercing this node
		RayInfoContainer *mRays;
		/// area of current node
		float mArea;
		/// geometry of current node induced by split planes
		VspBspNodeGeometry *mGeometry;

		/// pvs size
		int mPvs;
		
		/** Returns average ray contribution.
		*/
		float GetAvgRayContribution() const
		{
			return (float)mPvs / ((float)mRays->size() + Limits::Small);
		}


		VspBspTraversalData():
		mNode(NULL),
		mPolygons(NULL),
		mDepth(0),
		mViewCell(NULL),
		mRays(NULL),
		mPvs(0),
		mArea(0.0),
		mGeometry(NULL)
		{}
		
		VspBspTraversalData(VspBspNode *node, 
						 PolygonContainer *polys, 
						 const int depth, 
						 ViewCell *viewCell,
						 RayInfoContainer *rays,
						 int pvs,
						 float area,
						 VspBspNodeGeometry *cell): 
		mNode(node), 
		mPolygons(polys), 
		mDepth(depth), 
		mViewCell(viewCell),
		mRays(rays),
		mPvs(pvs),
		mArea(area),
		mGeometry(cell)
		{}
    };
	
	typedef std::stack<VspBspTraversalData> VspBspTraversalStack;

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

	~VspBspTree();

	const VspBspTreeStatistics &GetStatistics() const; 
  

	/** Constructs the tree from a given set of rays.
		@param sampleRays the set of sample rays the construction is based on
		@param viewCells if not NULL, new view cells are 
		created in the leafs and stored in the conatainer
	*/
	void Construct(const VssRayContainer &sampleRays);

	/** Returns list of BSP leaves.
	*/
	void CollectLeaves(vector<VspBspLeaf *> &leaves) const;

	/** Returns box which bounds the whole tree.
	*/
	AxisAlignedBox3 GetBoundingBox()const;

	/** Returns root of BSP tree.
	*/
	VspBspNode *GetRoot() const;

	/** Exports VspBsp tree to file.
	*/
	bool Export(const string filename);

	/** Collects the leaf view cells of the tree
		@param viewCells returns the view cells 
	*/
	void CollectViewCells(ViewCellContainer &viewCells) 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);

	/// bsp tree construction types
	enum {FROM_INPUT_VIEW_CELLS, FROM_SCENE_GEOMETRY, FROM_SAMPLES};

	/** Returns statistics.
	*/
	VspBspTreeStatistics &GetStat();

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

	/** Constructs geometry associated with the half space intersections 
		leading to this node.
	*/
	void ConstructGeometry(VspBspNode *n, PolygonContainer &cell) const;

	/** Constructs geometry associated with the half space intersections 
		leading to this node.
	*/
	void ConstructGeometry(BspViewCell *vc, PolygonContainer &cell) const;

	/** Construct geometry and stores it in a geometry node container.
	*/
	void ConstructGeometry(VspBspNode *n, VspBspNodeGeometry &cell) const;

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

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

	/** Returns true if merge criteria are reached.
	*/
    bool ShouldMerge(VspBspLeaf *front, VspBspLeaf *back) const;

	/** Merges view cells based on some criteria
	    E.g., empty view cells can pe purged, view cells which have 
		a very similar PVS can be merged to one larger view cell.

		@returns true if merge was successful.
	*/
	bool MergeViewCells(VspBspLeaf *front, VspBspLeaf *back) const;

	/** Traverses tree and counts all view cells as well as their PVS size.
	*/
	void EvaluateViewCellsStats(VspBspViewCellsStatistics &stat) const;


	/** Returns view cell corresponding to unbounded space.
	*/
	BspViewCell *GetRootCell() const;

protected:

	// --------------------------------------------------------------
	// For sorting objects
	// --------------------------------------------------------------
	struct SortableEntry
	{
		enum {POLY_MIN, POLY_MAX};
    
		int type;
		float value;
		Polygon3 *poly;
		SortableEntry() {}
		SortableEntry(const int t, const float v, Polygon3 *poly): 
		type(t), value(v), poly(poly) {}
		
		bool operator<(const SortableEntry &b) const 
		{
			return value < b.value;
		}  
	};

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

	/** Subdivides node with respect to the traversal data.
	    @param tStack current traversal stack
		@param tData traversal data also holding node to be subdivided
		@returns new root of the subtree
	*/
	VspBspNode *Subdivide(VspBspTraversalStack &tStack, VspBspTraversalData &tData);

	/** Constructs the tree from the given list of polygons and rays.
		@param polys stores set of polygons on which subdivision may be based
		@param rays storesset of rays on which subdivision may be based
	*/
	void Construct(PolygonContainer *polys, RayInfoContainer *rays);

	/** Selects the best possible splitting plane. 
		@param leaf the leaf to be split
		@param polys the polygon list on which the split decition is based
		@param rays ray container on which selection may be based
		@note the polygons can be reordered in the process
		@returns the split plane
	*/
	Plane3 SelectPlane(VspBspLeaf *leaf, 
					   VspBspTraversalData &data);

	
	/** Strategies where the effect of the split plane is tested
	    on all input rays.

		@returns the cost of the candidate split plane
	*/
	float SplitPlaneCost(const Plane3 &candidatePlane, 
						 const VspBspTraversalData &data);



	/** Subdivide 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
	*/

	VspBspInterior *SubdivideNode(VspBspTraversalData &tData,
							   VspBspTraversalData &frontData,
							   VspBspTraversalData &backData,
							   PolygonContainer &coincident);

	/** Selects the split plane in order to construct a tree with
		certain characteristics (e.g., balanced tree, least splits, 
		2.5d aligned)
		@param polygons container of polygons
		@param rays bundle of rays on which the split can be based
	*/
	Plane3 SelectPlaneHeuristics(VspBspLeaf *leaf,
								 VspBspTraversalData &data);

	/** Extracts the meshes of the objects and adds them to polygons. 
		Adds object aabb to the aabb of the tree.
		@param maxPolys the maximal number of objects to be stored as polygons
		@returns the number of polygons
	*/
	int AddToPolygonSoup(const ObjectContainer &objects, 
						 PolygonContainer &polys, 
						 int maxObjects = 0);

	/** Extracts the meshes of the view cells and and adds them to polygons.
		Adds view cell aabb to the aabb of the tree.
		@param maxPolys the maximal number of objects to be stored as polygons
		@returns the number of polygons
	*/
	int AddToPolygonSoup(const ViewCellContainer &viewCells, 
						 PolygonContainer &polys, 
						 int maxObjects = 0);

	/** Extract polygons of this mesh and add to polygon container.
		@param mesh the mesh that drives the polygon construction
		@param parent the parent intersectable this polygon is constructed from
		@returns number of polygons
	*/
	int AddMeshToPolygons(Mesh *mesh, PolygonContainer &polys, MeshInstance *parent);

	/** returns next candidate index and reorders polygons so no candidate is chosen two times
		@param the current candidate index
		@param max the range of candidates
	*/
	int GetNextCandidateIdx(int currentIdx, PolygonContainer &polys);
	
	/** Computes best cost ratio for the suface area heuristics for axis aligned
		splits. This heuristics minimizes the cost for ray traversal.
		@param polys the polygons guiding the ratio computation
		@param box the bounding box of the leaf
		@param axis the current split axis
		@param position returns the split position
		@param objectsBack the number of objects in the back of the split plane
		@param objectsFront the number of objects in the front of the split plane
	*/
	float BestCostRatio(const PolygonContainer &polys,
						const AxisAlignedBox3 &box,
						const int axis,
						float &position,
						int &objectsBack,
						int &objectsFront) const;
	
	/** Sorts split candidates for surface area heuristics for axis aligned splits.
		@param polys the input for choosing split candidates
		@param axis the current split axis
		@param splitCandidates returns sorted list of split candidates
	*/
	void SortSplitCandidates(const PolygonContainer &polys, 
							 const int axis, 
							 vector<SortableEntry> &splitCandidates) const;

	/** Selects an axis aligned split plane.
		Returns true if split is valied
	*/
	bool SelectAxisAlignedPlane(Plane3 &plane, const PolygonContainer &polys) const;

	/** Bounds ray and returns minT and maxT.
		@returns true if ray hits BSP tree bounding box
	*/
	bool BoundRay(const Ray &ray, float &minT, float &maxT) const;

	/** Subdivides the rays into front and back rays according to the split plane.
		
		@param plane the split plane
		@param rays contains the rays to be split. The rays are 
			   distributed into front and back rays.
		@param frontRays returns rays on the front side of the plane
		@param backRays returns rays on the back side of the plane
		
		@returns the number of splits
	*/
	int SplitRays(const Plane3 &plane,
				  RayInfoContainer &rays, 
			      RayInfoContainer &frontRays, 
				  RayInfoContainer &backRays);


	/** Extracts the split planes representing the space bounded by node n.
	*/
	void ExtractHalfSpaces(VspBspNode *n, vector<Plane3> &halfSpaces) const;

	/** Adds the object to the pvs of the front and back leaf with a given classification.

		@param obj the object to be added
		@param cf the ray classification regarding the split plane
		@param frontPvs returns the PVS of the front partition
		@param backPvs returns the PVS of the back partition
	
	*/
	void AddObjToPvs(Intersectable *obj, const int cf, int &frontPvs, int &backPvs) const;
	
	/** Computes PVS size induced by the rays.
	*/
	int ComputePvsSize(const RayInfoContainer &rays) const;

	/** Returns true if tree can be terminated.
	*/
	inline bool TerminationCriteriaMet(const VspBspTraversalData &data) const;

	/** Computes accumulated ray lenght of this rays.
	*/
	float AccumulatedRayLength(const RayInfoContainer &rays) const;



	/// Pointer to the root of the tree
	VspBspNode *mRoot;
		
	VspBspTreeStatistics mStat;

	/// Strategies for choosing next split plane.
	enum {NO_STRATEGY = 0,
		  RANDOM_POLYGON = 1, 
		  AXIS_ALIGNED = 2,
		  LEAST_SPLITS = 4, 
		  BALANCED_POLYS = 8,
		  BALANCED_VIEW_CELLS = 16,
		  LARGEST_POLY_AREA = 32,
		  VERTICAL_AXIS = 64,
		  BLOCKED_RAYS = 128,
		  LEAST_RAY_SPLITS = 256,
		  BALANCED_RAYS = 512,
		  PVS = 1024
		};

	/// box around the whole view domain
	AxisAlignedBox3 mBox;

	/// view cell corresponding to unbounded space
	BspViewCell *mRootCell;

	/// minimal number of rays before subdivision termination
	int mTermMinRays;
	/// maximal possible depth
	int mTermMaxDepth;
	/// mininum area
	float mTermMinArea;
	/// mininum PVS
	int mTermMinPvs;

	/// minimal number of rays for axis aligned split
	int mTermMinRaysForAxisAligned;
	/// minimal number of objects for axis aligned split
	int mTermMinObjectsForAxisAligned;
	/// maximal contribution per ray
	float mTermMaxRayContribution;
	/// minimal accumulated ray length
	float mTermMinAccRayLength;


	/// strategy to get the best split plane
	int mSplitPlaneStrategy;
	/// number of candidates evaluated for the next split plane
	int mMaxPolyCandidates;
	/// number of candidates for split planes evaluated using the rays
	int mMaxRayCandidates;
	
	float mCtDivCi;

	/// axis aligned split criteria
	float mAaCtDivCi;
	float mSplitBorder;
	float mMaxCostRatio;

	// factors guiding the split plane heuristics
	float mBlockedRaysFactor;
	float mLeastRaySplitsFactor;
	float mBalancedRaysFactor;
	float mPvsFactor;
	float mLeastSplitsFactor;

	//-- thresholds used for view cells merge
	int mMinPvsDif;
	int mMinPvs;
	int mMaxPvs;

	/// if area or accumulated ray lenght should be used for PVS heuristics
	bool mPvsUseArea;

private:
	
	static const float sLeastRaySplitsTable[5];
	/** Evaluates split plane classification with respect to the plane's 
		contribution for balanced rays.
	*/
	static const float sBalancedRaysTable[5];

	/// Generates unique ids for PVS criterium
	static void GenerateUniqueIdsForPvs();

	//-- unique ids for PVS criterium
	static int sFrontId; 
	static int sBackId;
	static int sFrontAndBackId;
};

#endif