/*=========================================================================
 *
 *  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 itkSobelEdgeDetectionImageFilter_hxx
#define itkSobelEdgeDetectionImageFilter_hxx

#include "itkNeighborhoodOperatorImageFilter.h"
#include "itkSobelOperator.h"
#include "itkNaryAddImageFilter.h"
#include "itkMultiplyImageFilter.h"
#include "itkSqrtImageFilter.h"

namespace itk
{
template <typename TInputImage, typename TOutputImage>
void
SobelEdgeDetectionImageFilter<TInputImage, TOutputImage>::GenerateInputRequestedRegion()
{
  // call the superclass' implementation of this method. this should
  // copy the output requested region to the input requested region
  Superclass::GenerateInputRequestedRegion();

  // get pointers to the input and output
  const InputImagePointer inputPtr = const_cast<TInputImage *>(this->GetInput());

  if (!inputPtr)
  {
    return;
  }

  // Build an operator so that we can determine the kernel size
  SobelOperator<OutputPixelType, ImageDimension> oper;
  oper.CreateDirectional();

  // get a copy of the input requested region (should equal the output
  // requested region)
  typename TInputImage::RegionType inputRequestedRegion = inputPtr->GetRequestedRegion();

  // pad the input requested region by the operator radius
  inputRequestedRegion.PadByRadius(oper.GetRadius());

  // crop the input requested region at the input's largest possible region
  if (inputRequestedRegion.Crop(inputPtr->GetLargestPossibleRegion()))
  {
    inputPtr->SetRequestedRegion(inputRequestedRegion);
    return;
  }

  // Couldn't crop the region (requested region is outside the largest
  // possible region).  Throw an exception.

  // store what we tried to request (prior to trying to crop)
  inputPtr->SetRequestedRegion(inputRequestedRegion);

  // build an exception
  InvalidRequestedRegionError e(__FILE__, __LINE__);
  e.SetLocation(ITK_LOCATION);
  e.SetDescription("Requested region is (at least partially) outside the largest possible region.");
  e.SetDataObject(inputPtr);
  throw e;
}

template <typename TInputImage, typename TOutputImage>
void
SobelEdgeDetectionImageFilter<TInputImage, TOutputImage>::GenerateData()
{
  // Test whether the output pixel type (or its components) are not of type
  // float or double:
  if (NumericTraits<OutputPixelType>::is_integer)
  {
    itkWarningMacro("Output pixel type MUST be float or double to prevent computational errors");
  }

  // Define the filter types used.
  using OpFilter = NeighborhoodOperatorImageFilter<InputImageType, OutputImageType>;
  using MultFilter = MultiplyImageFilter<OutputImageType, OutputImageType, OutputImageType>;
  using AddFilter = NaryAddImageFilter<OutputImageType, OutputImageType>;
  using SqrtFilter = SqrtImageFilter<OutputImageType, OutputImageType>;

  const typename TOutputImage::Pointer output = this->GetOutput();
  output->SetBufferedRegion(output->GetRequestedRegion());
  output->Allocate();

  // Create the Sobel operator
  SobelOperator<OutputPixelType, ImageDimension> opers[ImageDimension];
  ZeroFluxNeumannBoundaryCondition<TInputImage>  nbc;

  // Setup mini-pipelines along each axis.
  typename OpFilter::Pointer   opFilter[ImageDimension];
  typename MultFilter::Pointer multFilter[ImageDimension];
  auto                         addFilter = AddFilter::New();
  auto                         sqrtFilter = SqrtFilter::New();
  for (unsigned int i = 0; i < ImageDimension; ++i)
  {
    // Create the filters for this axis.
    opFilter[i] = OpFilter::New();
    multFilter[i] = MultFilter::New();

    // Set boundary condition and operator for this axis.
    opers[i].UseLegacyCoefficients(m_UseLegacyOperatorCoefficients);
    opers[i].SetDirection(i);
    opers[i].CreateDirectional();
    opFilter[i]->OverrideBoundaryCondition(&nbc);
    opFilter[i]->SetOperator(opers[i]);

    // Setup the mini-pipeline for this axis.
    opFilter[i]->SetInput(this->GetInput());
    multFilter[i]->SetInput1(opFilter[i]->GetOutput());
    multFilter[i]->SetInput2(opFilter[i]->GetOutput());

    // All axes' mini-pipelines come together in addFilter.
    addFilter->SetInput(i, multFilter[i]->GetOutput());
  }

  // calculate the gradient magnitude
  sqrtFilter->SetInput(addFilter->GetOutput());

  // setup the mini-pipeline to calculate the correct regions and
  // write to the appropriate bulk data block
  sqrtFilter->GraftOutput(this->GetOutput());

  // execute the mini-pipeline
  sqrtFilter->Update();

  // graft the mini-pipeline output back onto this filter's output.
  // this is needed to get the appropriate regions passed back.
  this->GraftOutput(sqrtFilter->GetOutput());
}
} // end namespace itk

#endif
