// Copyright 2020-2021 Intel Corporation
// SPDX-License-Identifier: Apache-2.0

#pragma once

// ---------------------------------------------------------------------------
// Step through a DDA hierarchy.
//
// Note: We generate files HDDA_level>.ih from this 
//       template using CMake.
// ---------------------------------------------------------------------------

#if (@VKL_VDB_NEXT_LEVEL@) < VKL_VDB_NUM_LEVELS
  #include "HDDA_@VKL_VDB_NEXT_LEVEL@.ih"
#endif

/*
 * Step once in the hierarchy.
 * This potentially steps once on each level.
 *
 * Precondition: desc points to a voxel on some level. The goal
 * of hddaStep is to leave this voxel.
 */
#if @VKL_VDB_LEVEL@ == 0
void hddaStep(const VdbGrid *uniform grid, 
              const VdbVoxelDescriptor &desc,
              DdaState &dda)
{
#else
bool hddaStep_@VKL_VDB_LEVEL@(const VdbGrid *uniform grid, 
                              const VdbVoxelDescriptor &desc,
                              DdaState &dda)
{
#endif

  // We traverse depth-first to step on the lowest level possible.
  const bool lowestLevel = (desc.level == @VKL_VDB_LEVEL@);
  bool stepped = false;

  // First case: we can potentially descend to the next level.
#if @VKL_VDB_NEXT_LEVEL@ < @VKL_VDB_NUM_LEVELS@
  const uniform uint32 ox = DDA_STATE_X_OFFSET(@VKL_VDB_LEVEL@);
  const uniform uint32 oy = DDA_STATE_Y_OFFSET(@VKL_VDB_LEVEL@);
  const uniform uint32 oz = DDA_STATE_Z_OFFSET(@VKL_VDB_LEVEL@);
  if (lowestLevel)
  {
    const int32 oldx = dda.idx[ox];
    const int32 oldy = dda.idx[oy];
    const int32 oldz = dda.idx[oz];
    ddaStep(dda, @VKL_VDB_LEVEL@);
    stepped = true;

    if (@VKL_VDB_LEVEL@ < dda.level)
    {
      // We are on the same level as the voxel described by desc, 
      // but that is NOT the lowest level dda state.
      // Reinitialize the lower levels to keep them consistent.
      // This keeps the dda state consistent towards the leaf level.
      // If this level moved in x-dimension, then all lower levels
      // will move by the same amount in x-dimension. y and z must be 
      // recomputed, however, as must tNext for x and y.
      const int32 dx = dda.idx[ox]-oldx;
      const int32 dy = dda.idx[oy]-oldy;
      const int32 dz = dda.idx[oz]-oldz;
      ddaReinitBelow(dda, @VKL_VDB_LEVEL@, dx, dy, dz);
    }
  }
  else
  {
    if (hddaStep_@VKL_VDB_NEXT_LEVEL@(grid, desc, dda))
    {
      // We check if the child has left our domain and follow it if it has.
      // This keeps the dda state consistent towards the root node.
      const uniform int32 cellRes = VKL_VDB_RES_@VKL_VDB_NEXT_LEVEL@;
      const uniform uint32 cox = DDA_STATE_X_OFFSET(@VKL_VDB_NEXT_LEVEL@);
      const uniform uint32 coy = DDA_STATE_Y_OFFSET(@VKL_VDB_NEXT_LEVEL@);
      const uniform uint32 coz = DDA_STATE_Z_OFFSET(@VKL_VDB_NEXT_LEVEL@);
      const bool childHasLeftDomain = dda.idx[cox] < dda.idx[ox]
                                   || dda.idx[coy] < dda.idx[oy]
                                   || dda.idx[coz] < dda.idx[oz]
                                   || dda.idx[cox] >= (dda.idx[ox] + cellRes)
                                   || dda.idx[coy] >= (dda.idx[oy] + cellRes)
                                   || dda.idx[coz] >= (dda.idx[oz] + cellRes);
      if (childHasLeftDomain) {
        ddaStep(dda, @VKL_VDB_LEVEL@);
        stepped = true;
      }
    }
  }

  // Second case: We cannot descend because there is no next level.
#else // @VKL_VDB_NEXT_LEVEL@ < @VKL_VDB_NUM_LEVELS@
  assert(lowestLevel);
  ddaStep(dda, @VKL_VDB_LEVEL@);
  stepped = true;
#endif

#if @VKL_VDB_LEVEL@ > 0
  return stepped;
#endif
}