/*=========================================================================
 *
 *  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.
 *
 *=========================================================================*/
#include "itkThreadedIndexedContainerPartitioner.h"
#include "itkMath.h"

namespace itk
{

ThreadedIndexedContainerPartitioner::ThreadedIndexedContainerPartitioner() = default;

ThreadedIndexedContainerPartitioner::~ThreadedIndexedContainerPartitioner() = default;

ThreadIdType
ThreadedIndexedContainerPartitioner::PartitionDomain(const ThreadIdType threadId,
                                                     const ThreadIdType requestedTotal,
                                                     const DomainType & completeIndexRange,
                                                     DomainType &       subIndexRange) const
{
  // completeIndexRange and subIndexRange are inclusive

  // determine the actual number of pieces that will be generated
  const auto         count = static_cast<double>(completeIndexRange[1] - completeIndexRange[0] + 1);
  auto               valuesPerThread = Math::Ceil<ThreadIdType>(count / static_cast<double>(requestedTotal));
  const ThreadIdType maxThreadIdUsed = Math::Ceil<ThreadIdType>(count / static_cast<double>(valuesPerThread)) - 1;

  // Split the index range
  if (threadId < maxThreadIdUsed)
  {
    subIndexRange[0] = completeIndexRange[0] + threadId * valuesPerThread;
    subIndexRange[1] = subIndexRange[0] + valuesPerThread - 1;
  }
  if (threadId == maxThreadIdUsed)
  {
    subIndexRange[0] = completeIndexRange[0] + threadId * valuesPerThread;
    // last thread needs to process the "rest" of the range
    subIndexRange[1] = completeIndexRange[1];
  }

  itkDebugMacro("ThreadedIndexedContainerPartitioner:  Split : " << subIndexRange);

  return maxThreadIdUsed + 1;
}

} // end namespace itk
