/*=========================================================================

  Program:   Visualization Toolkit
  Module:    vtkSimpleScalarTree.h

  Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
  All rights reserved.
  See Copyright.txt or http://www.kitware.com/Copyright.htm for details.

     This software is distributed WITHOUT ANY WARRANTY; without even
     the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
     PURPOSE.  See the above copyright notice for more information.

=========================================================================*/
// .NAME vtkSimpleScalarTree - organize data according to scalar values (used to accelerate contouring operations)
// .SECTION Description
// vtkSimpleScalarTree creates a pointerless binary tree that helps search
// for cells that lie within a particular scalar range. This object is used
// to accelerate some contouring (and other scalar-based techniques).
//
// The tree consists of an array of (min,max) scalar range pairs per
// node in the tree. The (min,max) range is determined from looking at
// the range of the children of the tree node. If the node is a leaf,
// then the range is determined by scanning the range of scalar data
// in n cells in the dataset. The n cells are determined by arbitrary
// selecting cell ids from id(i) to id(i+n), and where n is specified
// using the BranchingFactor ivar. Note that leaf node i=0 contains
// the scalar range computed from cell ids (0,n-1); leaf node i=1
// contains the range from cell ids (n,2n-1); and so on. The
// implication is that there are no direct lists of cell ids per leaf
// node, instead the cell ids are implicitly known. Despite the
// arbitrary grouping of cells, in practice this scalar tree actually
// performs quite well due to spatial/data coherence.
//
// This class has an API that supports both serial and parallel
// operation.  The parallel API enables the using class to grab arrays
// (or batches) of cells that potentially intersect the
// isocontour. These batches can then be processed in separate
// threads.

// .SECTION See Also
// vtkSpanSpace

#ifndef vtkSimpleScalarTree_h
#define vtkSimpleScalarTree_h

#include "vtkCommonExecutionModelModule.h" // For export macro
#include "vtkScalarTree.h"

class vtkScalarNode;

class VTKCOMMONEXECUTIONMODEL_EXPORT vtkSimpleScalarTree : public vtkScalarTree
{
public:
  // Description:
  // Instantiate scalar tree with maximum level of 20 and branching
  // factor of three.
  static vtkSimpleScalarTree *New();

  // Description:
  // Standard type related macros and PrintSelf() method.
  vtkTypeMacro(vtkSimpleScalarTree,vtkScalarTree);
  void PrintSelf(ostream& os, vtkIndent indent) VTK_OVERRIDE;

  // Description:
  // Set the branching factor for the tree. This is the number of
  // children per tree node. Smaller values (minimum is 2) mean deeper
  // trees and more memory overhead. Larger values mean shallower
  // trees, less memory usage, but worse performance.
  vtkSetClampMacro(BranchingFactor,int,2,VTK_INT_MAX);
  vtkGetMacro(BranchingFactor,int);

  // Description:
  // Get the level of the scalar tree. This value may change each time the
  // scalar tree is built and the branching factor changes.
  vtkGetMacro(Level,int);

  // Description:
  // Set the maximum allowable level for the tree.
  vtkSetClampMacro(MaxLevel,int,1,VTK_INT_MAX);
  vtkGetMacro(MaxLevel,int);

  // Description:
  // Construct the scalar tree from the dataset provided. Checks build times
  // and modified time from input and reconstructs the tree if necessary.
  virtual void BuildTree();

  // Description:
  // Initialize locator. Frees memory and resets object as appropriate.
  virtual void Initialize();

  // Description:
  // Begin to traverse the cells based on a scalar value. Returned cells
  // will likely have scalar values that span the scalar value specified.
  virtual void InitTraversal(double scalarValue);

  // Description:
  // Return the next cell that may contain scalar value specified to
  // initialize traversal. The value NULL is returned if the list is
  // exhausted. Make sure that InitTraversal() has been invoked first or
  // you'll get erratic behavior.
  virtual vtkCell *GetNextCell(vtkIdType &cellId, vtkIdList* &ptIds,
                               vtkDataArray *cellScalars);

  // The following methods supports parallel (threaded)
  // applications. Basically batches of cells (which represent a
  // portion of the whole dataset) are available for processing in a
  // parallel For() operation.

  // Description:
  // Get the number of cell batches available for processing. Note
  // that this methods should be called after InitTraversal(). This is
  // because the number of batches available is typically a function
  // of the isocontour value. Note that the cells found in
  // [0...(NumberOfCellBatches-1)] will contain all the cells
  // potentially containing the isocontour.
  virtual vtkIdType GetNumberOfCellBatches();

  // Description:
  // Return the array of cell ids in the specified batch. The method
  // also returns the number of cell ids in the array. Make sure to
  // call InitTraversal() beforehand.
  virtual const vtkIdType* GetCellBatch(vtkIdType batchNum,
                                        vtkIdType& numCells);

protected:
  vtkSimpleScalarTree();
  ~vtkSimpleScalarTree();

  int MaxLevel;
  int Level;
  int BranchingFactor; //number of children per node
  vtkScalarNode *Tree; //pointerless scalar range tree
  int TreeSize; //allocated size of tree
  vtkIdType LeafOffset; //offset to leaf nodes of tree

private:
  vtkIdType NumCells; //the number of cells in this dataset
  vtkIdType TreeIndex; //traversal location within tree
  int       ChildNumber; //current child in traversal
  vtkIdType CellId; //current cell id being examined
  int       FindStartLeaf(vtkIdType index, int level);
  int       FindNextLeaf(vtkIdType index,int level);

  vtkIdType *CandidateCells; //to support parallel computing
  vtkIdType  NumCandidates;

private:
  vtkSimpleScalarTree(const vtkSimpleScalarTree&) VTK_DELETE_FUNCTION;
  void operator=(const vtkSimpleScalarTree&) VTK_DELETE_FUNCTION;
};

#endif
