/*=========================================================================
 *
 *  Copyright NumFOCUS
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *         https://www.apache.org/licenses/LICENSE-2.0.txt
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 *=========================================================================*/
#ifndef itkUniformRandomSpatialNeighborSubsampler_hxx
#define itkUniformRandomSpatialNeighborSubsampler_hxx
#include <set>

namespace itk
{
namespace Statistics
{

template <typename TSample, typename TRegion>
UniformRandomSpatialNeighborSubsampler<TSample, TRegion>::UniformRandomSpatialNeighborSubsampler()
{
  m_RandomNumberGenerator = RandomGeneratorType::New();
  m_UseClockForSeed = false;
  m_RandomNumberGenerator->SetSeed(this->m_Seed);
  m_NumberOfResultsRequested = 0;
}

template <typename TSample, typename TRegion>
typename LightObject::Pointer
UniformRandomSpatialNeighborSubsampler<TSample, TRegion>::InternalClone() const
{
  typename LightObject::Pointer loPtr = Superclass::InternalClone();

  typename Self::Pointer rval = dynamic_cast<Self *>(loPtr.GetPointer());
  if (rval.IsNull())
  {
    itkExceptionMacro("downcast to type " << this->GetNameOfClass() << " failed.");
  }

  rval->m_NumberOfResultsRequested = this->m_NumberOfResultsRequested;
  rval->SetSeed(this->m_Seed);
  rval->SetUseClockForSeed(this->m_UseClockForSeed);
  return loPtr;
}

template <typename TSample, typename TRegion>
void
UniformRandomSpatialNeighborSubsampler<TSample, TRegion>::Search(const InstanceIdentifier & query,
                                                                 SubsamplePointer &         results)
{
  if (!this->m_RadiusInitialized)
  {
    itkExceptionMacro("Radius not set.");
  }
  if (!this->m_SampleRegionInitialized)
  {
    itkExceptionMacro("Sample region not set.");
  }
  if (!this->GetRegionConstraintInitialized())
  {
    this->SetRegionConstraint(this->m_SampleRegion);
  }

  results->Clear();
  results->SetSample(this->m_Sample);

  IndexType searchStartIndex;
  IndexType searchEndIndex;

  IndexType constraintIndex = this->m_RegionConstraint.GetIndex();
  SizeType  constraintSize = this->m_RegionConstraint.GetSize();

  IndexType                            queryIndex;
  typename RegionType::OffsetTableType offsetTable;
  this->m_SampleRegion.ComputeOffsetTable(offsetTable);
  ImageHelperType::ComputeIndex(this->m_SampleRegion.GetIndex(), query, offsetTable, queryIndex);

  unsigned int numberOfPoints = 1;

  for (unsigned int dim = 0; dim < RegionType::ImageDimension; ++dim)
  {
    if (queryIndex[dim] < static_cast<IndexValueType>(this->m_Radius[dim]))
    {
      searchStartIndex[dim] = std::max(IndexValueType{}, constraintIndex[dim]);
    }
    else
    {
      searchStartIndex[dim] =
        std::max(static_cast<IndexValueType>(queryIndex[dim] - this->m_Radius[dim]), constraintIndex[dim]);
    }

    if (queryIndex[dim] + this->m_Radius[dim] < constraintIndex[dim] + constraintSize[dim])
    {
      searchEndIndex[dim] = queryIndex[dim] + this->m_Radius[dim];
    }
    else
    {
      searchEndIndex[dim] = (constraintIndex[dim] + constraintSize[dim]) - 1;
    }
    numberOfPoints = numberOfPoints * (searchEndIndex[dim] - searchStartIndex[dim] + 1);
  }

  if (!this->m_RegionConstraint.IsInside(queryIndex))
  {
    itkWarningMacro("query point (" << query << ") corresponding to index (" << queryIndex
                                    << ") is not inside the given image region (" << this->m_RegionConstraint
                                    << ").  No matching points found.");
    return;
  }

  if (!this->m_RequestMaximumNumberOfResults && (m_NumberOfResultsRequested < numberOfPoints))
  {
    numberOfPoints = m_NumberOfResultsRequested;
  }

  unsigned int pointsFound = 0;

  std::set<InstanceIdentifier>         usedIds;
  typename RegionType::OffsetValueType offset;

  // The trouble with decoupling the region from the sample is that
  // there is an implicit assumption that the instance identifiers in the sample
  // are ordered as if someone was iterating forward through the region
  // TODO Is this a safe assumption to make?
  if (this->m_CanSelectQuery)
  {
    // This case will be faster since it doesn't need to check
    // whether the selected index matches the query index
    while (pointsFound < numberOfPoints)
    {
      // randomly select an index
      IndexType index;
      for (unsigned int dim = 0; dim < RegionType::ImageDimension; ++dim)
      {
        index[dim] = this->GetIntegerVariate(searchStartIndex[dim], searchEndIndex[dim], queryIndex[dim]);
      }
      offset = 0;
      ImageHelperType::ComputeOffset(this->m_SampleRegion.GetIndex(), index, offsetTable, offset);

      results->AddInstance(static_cast<InstanceIdentifier>(offset));
      ++pointsFound;
    }
  }
  else
  {
    while (pointsFound < numberOfPoints)
    {
      // randomly select an index
      IndexType index;
      for (unsigned int dim = 0; dim < RegionType::ImageDimension; ++dim)
      {
        index[dim] = this->GetIntegerVariate(searchStartIndex[dim], searchEndIndex[dim], queryIndex[dim]);
      }
      // only include this index if it is not the query point
      if (index != queryIndex)
      {
        offset = 0;
        ImageHelperType::ComputeOffset(this->m_SampleRegion.GetIndex(), index, offsetTable, offset);
        results->AddInstance(static_cast<InstanceIdentifier>(offset));
        ++pointsFound;
      }
    }
  }
} // end Search method

template <typename TSample, typename TRegion>
auto
UniformRandomSpatialNeighborSubsampler<TSample, TRegion>::GetIntegerVariate(RandomIntType lowerBound,
                                                                            RandomIntType upperBound,
                                                                            RandomIntType itkNotUsed(mean))
  -> RandomIntType
{
  RandomIntType sizeRange = upperBound - lowerBound;
  // mean ignored since we are uniformly sampling
  return lowerBound + m_RandomNumberGenerator->GetIntegerVariate(sizeRange);
}

template <typename TSample, typename TRegion>
void
UniformRandomSpatialNeighborSubsampler<TSample, TRegion>::PrintSelf(std::ostream & os, Indent indent) const
{
  Superclass::PrintSelf(os, indent);

  os << indent << "Number of results requested: " << m_NumberOfResultsRequested << std::endl;
  os << indent << "Use clock for seed: " << m_UseClockForSeed << std::endl;
  os << std::endl;
}

} // end namespace Statistics
} // end namespace itk

#endif