/** Small helper classes to optimise finding vertizes close to a given location */
#ifndef AI_SPATIALSORT_H_INC
#define AI_SPATIALSORT_H_INC

#include <vector>
#include "../include/aiVector3D.h"

namespace Assimp
{

// ------------------------------------------------------------------------------------------------
/** A little helper class to quickly find all vertices in the epsilon environment of a given
 * position. Construct an instance with an array of positions. The class stores the given positions
 * by their indices and sorts them by their distance to an arbitrary chosen plane.
 * You can then query the instance for all vertices close to a given position in an average O(log n) 
 * time, with O(n) worst case complexity when all vertices lay on the plane. The plane is chosen
 * so that it avoids common planes in usual data sets.
 */
class SpatialSort
{
public:

	SpatialSort() {/* This is unintialized. This is evil. This is OK. */}

	/** Constructs a spatially sorted representation from the given position array.
	 * Supply the positions in its layout in memory, the class will only refer to them
	 * by index.
	 * @param pPositions Pointer to the first position vector of the array.
	 * @param pNumPositions Number of vectors to expect in that array.
	 * @param pElementOffset Offset in bytes from the beginning of one vector in memory to the beginning of the next vector.
	 */
	SpatialSort( const aiVector3D* pPositions, unsigned int pNumPositions, unsigned int pElementOffset);

	/** Destructor */
	~SpatialSort();

	/** Returns an iterator for all positions close to the given position.
	 * @param pPosition The position to look for vertices.
	 * @param pRadius Maximal distance from the position a vertex may have to be counted in.
	 * @param poResults The container to store the indices of the found positions. Will be emptied
	 *   by the call so it may contain anything.
	 * @return An iterator to iterate over all vertices in the given area.
	 */
	void FindPositions( const aiVector3D& pPosition, float pRadius, std::vector<unsigned int>& poResults) const;

protected:
	/** Normal of the sorting plane, normalized. The center is always at (0, 0, 0) */
	aiVector3D mPlaneNormal;

	/** An entry in a spatially sorted position array. Consists of a vertex index,
	 * its position and its precalculated distance from the reference plane */
	struct Entry
	{
		unsigned int mIndex; ///< The vertex referred by this entry
		aiVector3D mPosition; ///< Position
		float mDistance; ///< Distance of this vertex to the sorting plane

		Entry() { /** intentionally not initialized.*/ }
		Entry( unsigned int pIndex, const aiVector3D& pPosition, float pDistance) 
			: mPosition( pPosition), mIndex( pIndex), mDistance( pDistance)
		{ 	}

		bool operator < (const Entry& e) const { return mDistance < e.mDistance; }
	};

	// all positions, sorted by distance to the sorting plane
	std::vector<Entry> mPositions;
};

} // end of namespace Assimp

#endif // AI_SPATIALSORT_H_INC