/*
 * This file belongs to the Galois project, a C++ library for exploiting parallelism.
 * The code is being released under the terms of the 3-Clause BSD License (a
 * copy is located in LICENSE.txt at the top-level directory).
 *
 * Copyright (C) 2018, The University of Texas at Austin. All rights reserved.
 * UNIVERSITY EXPRESSLY DISCLAIMS ANY AND ALL WARRANTIES CONCERNING THIS
 * SOFTWARE AND DOCUMENTATION, INCLUDING ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR ANY PARTICULAR PURPOSE, NON-INFRINGEMENT AND WARRANTIES OF
 * PERFORMANCE, AND ANY WARRANTY THAT MIGHT OTHERWISE ARISE FROM COURSE OF
 * DEALING OR USAGE OF TRADE.  NO WARRANTY IS EITHER EXPRESS OR IMPLIED WITH
 * RESPECT TO THE USE OF THE SOFTWARE OR DOCUMENTATION. Under no circumstances
 * shall University be liable for incidental, special, indirect, direct or
 * consequential damages or loss of profits, interruption of business, or
 * related expenses which may arise from use of Software or Documentation,
 * including but not limited to those resulting from defects in Software and/or
 * Documentation, or loss or inaccuracy of data of any kind.
 */

#ifndef KD_TREE_MEDIAN_SPLIT_H
#define KD_TREE_MEDIAN_SPLIT_H

template <bool CONCURRENT, typename T, typename GetPointFunc, typename DistFunc>
class KDtree {

public:
  static const unsigned SPLIT_X = 0;
  static const unsigned SPLIT_Y = 1;
  static const unsigned SPLIT_Z = 2;

  static const unsigned MAX_POINTS_IN_CELL = 8;

protected:
  using DataArray = galois::LargeArray<T*>;
  using AI        = typename DataArray::iterator;

  struct KDcell {
    unsigned mSplitType;
    double mSplitVal;
    AI mBeg;
    AI mEnd;
    KDtree* mLeftChild;
    KDtree* mRightChild;
  };

  using CellAlloc =
      typename std::conditional<CONCURRENT, galois::FixedSizeAllocator<KDcell>,
                                std::allocator<KDCell>>::type;

  using PushBag = galois::PerThreadBag<T*>;

  GetPointFunc mGetPtFunc;
  DistFunc mDistFunc;

  KDcell* mRoot;

  PushBag mNextBag;
  DataArray mDataArray;
  CellAlloc mCellAlloc;

  KDcell* createCell(AI beg, AI end {
    KDcell* node = mCellAlloc.allocate(1);
    assert(node);
    mCellAlloc.construct(node, SPLIT_X, 0.0, beg, end, nullptr, nullptr);
  }

public:

  explicit KDtree(const GetPointFunc& getPtFunc=GetPointFunc(), const DistFunc& distFunc=DistFunc())
    :
      mGetPtFunc(getPtFunc),
      mDistFunc(distFunc),
      mRoot(nullptr)
  {}


  void pushNext(T* item) {
    mNextBag.push(item);
  }

  void buildNext(void) {
    copyBagToArray(); // TODO: implement

    KDcell* root = createCell(mDataArray.begin(), mDataArray.end());
    mRoot        = node;

    galois::for_each(galois::iterate({root}),
                     [&](KDcell* cell, auto& ctx) {
                       auto sz = std::distance(cell->mBeg, cell->mEnd);

                       if (sz > MAX_POINTS_IN_CELL) {

                         KDcell* left = createCell(...);
                       }
                     },
                     galois::no_aborts());


    
  }
};

#endif // KD_TREE_MEDIAN_SPLIT_H
