/*=========================================================================
 *
 *  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
 *
 *         http://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 itkVnlInverseFFTImageFilter_hxx
#define itkVnlInverseFFTImageFilter_hxx

#include "itkProgressReporter.h"
#include "itkVnlFFTCommon.h"
#include "itkVnlInverseFFTImageFilter.h"

namespace itk
{

template <typename TInputImage, typename TOutputImage>
void
VnlInverseFFTImageFilter<TInputImage, TOutputImage>::GenerateData()
{
  // Get pointers to the input and output.
  typename InputImageType::ConstPointer inputPtr = this->GetInput();
  typename OutputImageType::Pointer     outputPtr = this->GetOutput();

  if (!inputPtr || !outputPtr)
  {
    return;
  }

  // We don't have a nice progress to report, but at least this simple line
  // reports the beginning and the end of the process.
  ProgressReporter progress(this, 0, 1);

  const OutputSizeType outputSize = outputPtr->GetLargestPossibleRegion().GetSize();

  // Allocate output buffer memory
  outputPtr->SetBufferedRegion(outputPtr->GetRequestedRegion());
  outputPtr->Allocate();

  const InputPixelType * in = inputPtr->GetBufferPointer();

  unsigned int vectorSize = 1;
  for (unsigned int i = 0; i < ImageDimension; i++)
  {
    if (!VnlFFTCommon::IsDimensionSizeLegal(outputSize[i]))
    {
      itkExceptionMacro(<< "Cannot compute FFT of image with size " << outputSize
                        << ". VnlInverseFFTImageFilter operates "
                        << "only on images whose size in each dimension has"
                        << "only a combination of 2,3, and 5 as prime factors.");
    }
    vectorSize *= outputSize[i];
  }

  SignalVectorType signal(vectorSize);
  for (unsigned int i = 0; i < vectorSize; i++)
  {
    signal[i] = in[i];
  }

  OutputPixelType * out = outputPtr->GetBufferPointer();

  // call the proper transform, based on compile type template parameter
  VnlFFTCommon::VnlFFTTransform<OutputImageType> vnlfft(outputSize);
  vnlfft.transform(signal.data_block(), 1);

  // Copy the VNL output back to the ITK image.
  // Extract the real part of the signal.
  // Ideally, the normalization by the number of elements
  // should have been accounted for by the VNL inverse Fourier transform,
  // but it is not.  So, we take care of it by dividing the signal by
  // the vectorSize.
  for (unsigned int i = 0; i < vectorSize; i++)
  {
    out[i] = signal[i].real() / vectorSize;
  }
}

template <typename TInputImage, typename TOutputImage>
SizeValueType
VnlInverseFFTImageFilter<TInputImage, TOutputImage>::GetSizeGreatestPrimeFactor() const
{
  return VnlFFTCommon::GREATEST_PRIME_FACTOR;
}

} // namespace itk
#endif
