// Created on: 2014-01-09
// Created by: Denis BOGOLEPOV
// Copyright (c) 2013-2014 OPEN CASCADE SAS
//
// This file is part of Open CASCADE Technology software library.
//
// This library is free software; you can redistribute it and/or modify it under
// the terms of the GNU Lesser General Public License version 2.1 as published
// by the Free Software Foundation, with special exception defined in the file
// OCCT_LGPL_EXCEPTION.txt. Consult the file LICENSE_LGPL_21.txt included in OCCT
// distribution for complete text of the license and disclaimer of any warranty.
//
// Alternatively, this file may be used under the terms of Open CASCADE
// commercial license or contractual agreement.

#include <BVH_Sorter.hxx>

// =======================================================================
// function : BVH_SweepPlaneBuilder
// purpose  :
// =======================================================================
template<class T, int N>
BVH_SweepPlaneBuilder<T, N>::BVH_SweepPlaneBuilder (const Standard_Integer theLeafNodeSize,
                                                    const Standard_Integer theMaxTreeDepth)
: BVH_Builder<T, N> (theLeafNodeSize,
                     theMaxTreeDepth)
{
  //
}

// =======================================================================
// function : ~BVH_SweepPlaneBuilder
// purpose  :
// =======================================================================
template<class T, int N>
BVH_SweepPlaneBuilder<T, N>::~BVH_SweepPlaneBuilder()
{
  //
}

// =======================================================================
// function : BuildNode
// purpose  :
// =======================================================================
template<class T, int N>
void BVH_SweepPlaneBuilder<T, N>::BuildNode (BVH_Set<T, N>*         theSet,
                                             BVH_Tree<T, N>*        theBVH,
                                             const Standard_Integer theNode)
{
  const Standard_Integer aNodeBegPrimitive = theBVH->BegPrimitive (theNode);
  const Standard_Integer aNodeEndPrimitive = theBVH->EndPrimitive (theNode);
  const Standard_Integer aNodeNbPrimitives = theBVH->NbPrimitives (theNode);

  if (aNodeEndPrimitive - aNodeBegPrimitive < BVH_Builder<T, N>::myLeafNodeSize)
  {
    return; // node does not require partitioning
  }

  // Parameters for storing best split
  Standard_Integer aMinSplitAxis = -1;
  Standard_Integer aMinSplitIndex = 0;

  Standard_Real* aLftSet = new Standard_Real[aNodeNbPrimitives];
  Standard_Real* aRghSet = new Standard_Real[aNodeNbPrimitives];

  Standard_Real aMinSplitCost = std::numeric_limits<Standard_Real>::max();

  // Find best split
  for (Standard_Integer anAxis = 0; anAxis < (N < 4 ? N : 3); ++anAxis)
  {
    const T aNodeSize = BVHTools::VecComp<T, N>::Get (theBVH->MaxPoint (theNode), anAxis) -
                        BVHTools::VecComp<T, N>::Get (theBVH->MinPoint (theNode), anAxis);
    if (aNodeSize <= THE_NODE_MIN_SIZE)
    {
      continue;
    }

    BVH_Sorter<T, N>::Perform (theSet, anAxis, aNodeBegPrimitive, aNodeEndPrimitive);

    BVH_Box<T, N> aLftBox;
    BVH_Box<T, N> aRghBox;

    *aLftSet = std::numeric_limits<T>::max();
    *aRghSet = std::numeric_limits<T>::max();

    // Sweep from left
    for (Standard_Integer anIndex = 1; anIndex < aNodeNbPrimitives; ++anIndex)
    {
      aLftBox.Combine (theSet->Box (anIndex + aNodeBegPrimitive - 1));

      aLftSet[anIndex] = static_cast<Standard_Real> (aLftBox.Area());
    }

    // Sweep from right
    for (Standard_Integer anIndex = 1; anIndex < aNodeNbPrimitives; ++anIndex)
    {
      aRghBox.Combine (theSet->Box (aNodeEndPrimitive - anIndex + 1));

      aRghSet[anIndex] = static_cast<Standard_Real> (aRghBox.Area());
    }

    // Find best split using simplified SAH
    for (Standard_Integer aNbLft = 1, aNbRgh = aNodeNbPrimitives - 1; aNbLft < aNodeNbPrimitives; ++aNbLft, --aNbRgh)
    {
      Standard_Real aCost = (aLftSet[aNbLft] /* / aNodeArea */) * aNbLft +
                            (aRghSet[aNbRgh] /* / aNodeArea */) * aNbRgh;

      if (aCost < aMinSplitCost)
      {
        aMinSplitCost = aCost;
        aMinSplitAxis = anAxis;
        aMinSplitIndex = aNbLft;
      }
    }
  }

  if (aMinSplitAxis == -1)
  {
    return;
  }

  theBVH->SetInner (theNode);

  if (aMinSplitAxis != (N < 4 ? N - 1 : 2))
  {
    BVH_Sorter<T, N>::Perform (theSet, aMinSplitAxis, aNodeBegPrimitive, aNodeEndPrimitive);
  }

  BVH_Box<T, N> aMinSplitBoxLft;
  BVH_Box<T, N> aMinSplitBoxRgh;

  // Compute bounding boxes for selected split plane
  for (Standard_Integer anIndex = aNodeBegPrimitive; anIndex < aMinSplitIndex + aNodeBegPrimitive; ++anIndex)
  {
    aMinSplitBoxLft.Combine (theSet->Box (anIndex));
  }

  for (Standard_Integer anIndex = aNodeEndPrimitive; anIndex >= aMinSplitIndex + aNodeBegPrimitive; --anIndex)
  {
    aMinSplitBoxRgh.Combine (theSet->Box (anIndex));
  }

  const Standard_Integer aMiddle = aNodeBegPrimitive + aMinSplitIndex;

  static const Standard_Integer aLftNode = 1;
  static const Standard_Integer aRghNode = 2;

  // Setting up tasks for child nodes
  for (Standard_Integer aSide = aLftNode; aSide <= aRghNode; ++aSide)
  {
    typename BVH_Box<T, N>::BVH_VecNt aChildMinPoint = (aSide == aLftNode)
                                                     ? aMinSplitBoxLft.CornerMin()
                                                     : aMinSplitBoxRgh.CornerMin();
    typename BVH_Box<T, N>::BVH_VecNt aChildMaxPoint = (aSide == aLftNode)
                                                     ? aMinSplitBoxLft.CornerMax()
                                                     : aMinSplitBoxRgh.CornerMax();

    Standard_Integer aChildBegPrimitive = (aSide == aLftNode)
                                        ? aNodeBegPrimitive
                                        : aMiddle;
    Standard_Integer aChildEndPrimitive = (aSide == aLftNode)
                                        ? aMiddle - 1
                                        : aNodeEndPrimitive;

    Standard_Integer aChildIndex = theBVH->AddLeafNode (aChildMinPoint, aChildMaxPoint,
                                                        aChildBegPrimitive, aChildEndPrimitive);

    theBVH->Level (aChildIndex) = theBVH->Level (theNode) + 1;

    // Check to see if child node must be split
    const Standard_Integer aChildNbPimitives = (aSide == aLftNode)
                                             ? aMiddle - aNodeBegPrimitive
                                             : aNodeEndPrimitive - aMiddle + 1;

    if (aSide == aLftNode)
      theBVH->LeftChild (theNode) = aChildIndex;
    else
      theBVH->RightChild (theNode) = aChildIndex;

    const Standard_Boolean isLeaf = aChildNbPimitives <= BVH_Builder<T, N>::myLeafNodeSize
                                 || theBVH->Level (aChildIndex) >= BVH_Builder<T, N>::myMaxTreeDepth;

    if (!isLeaf)
    {
      BVH_Builder<T, N>::myTasksQueue.Append (aChildIndex);
    }

    BVH_Builder<T, N>::UpdateDepth (theBVH, theBVH->Level (aChildIndex));
  }
}