/*=========================================================================
 *
 *  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 itkVectorInterpolateImageFunction_h
#define itkVectorInterpolateImageFunction_h

#include "itkImageFunction.h"
#include "itkFixedArray.h"

namespace itk
{

/**
 * \class VectorInterpolateImageFunction
 * \brief Base class for all vector image interpolators.
 *
 * VectorInterpolateImageFunction is the base for all ImageFunctions that
 * interpolates image with vector pixel types. This function outputs
 * a return value of type Vector<double,Dimension>.
 *
 * This class is templated input image type and the coordinate
 * representation type.
 *
 * \warning This hierarchy of functions work only for images
 * with Vector-based pixel types. For scalar images use
 * InterpolateImageFunction.
 *
 * \sa InterpolateImageFunction
 * \ingroup ImageFunctions ImageInterpolators
 * \ingroup ITKImageFunction
 */
template <typename TInputImage, typename TCoordRep = double>
class ITK_TEMPLATE_EXPORT VectorInterpolateImageFunction
  : public ImageFunction<TInputImage, typename NumericTraits<typename TInputImage::PixelType>::RealType, TCoordRep>
{
public:
  ITK_DISALLOW_COPY_AND_MOVE(VectorInterpolateImageFunction);

  /** Extract the vector dimension from the pixel template parameter. */
  static constexpr unsigned int Dimension = TInputImage::PixelType::Dimension;

  /** Dimension underlying input image. */
  static constexpr unsigned int ImageDimension = TInputImage::ImageDimension;

  /** Standard class type aliases. */
  using Self = VectorInterpolateImageFunction;
  using Superclass =
    ImageFunction<TInputImage, typename NumericTraits<typename TInputImage::PixelType>::RealType, TCoordRep>;

  using Pointer = SmartPointer<Self>;
  using ConstPointer = SmartPointer<const Self>;

  /** \see LightObject::GetNameOfClass() */
  itkOverrideGetNameOfClassMacro(VectorInterpolateImageFunction);

  /** InputImageType type alias support */
  using typename Superclass::InputImageType;
  using PixelType = typename InputImageType::PixelType;
  using ValueType = typename PixelType::ValueType;
  using RealType = typename NumericTraits<ValueType>::RealType;

  /** Point type alias support */
  using typename Superclass::PointType;

  /** Index type alias support */
  using typename Superclass::IndexType;

  /** ContinuousIndex type alias support */
  using typename Superclass::ContinuousIndexType;

  /** Output type is RealType of TInputImage::PixelType. */
  using typename Superclass::OutputType;

  /** CoordRep type alias support */
  using CoordRepType = TCoordRep;

  /** Returns the interpolated image intensity at a
   * specified point position. No bounds checking is done.
   * The point is assume to lie within the image buffer.
   * ImageFunction::IsInsideBuffer() can be used to check bounds before
   * calling the method. */
  OutputType
  Evaluate(const PointType & point) const override
  {
    const ContinuousIndexType index =
      this->GetInputImage()->template TransformPhysicalPointToContinuousIndex<TCoordRep>(point);
    return (this->EvaluateAtContinuousIndex(index));
  }

  /** Interpolate the image at a continuous index position
   *
   * Returns the interpolated image intensity at a
   * specified index position. No bounds checking is done.
   * The point is assume to lie within the image buffer.
   *
   * Subclasses must override this method.
   *
   * ImageFunction::IsInsideBuffer() can be used to check bounds before
   * calling the method. */
  OutputType
  EvaluateAtContinuousIndex(const ContinuousIndexType & index) const override = 0;

  /** Interpolate the image at an index position.
   * Simply returns the image value at the
   * specified index position. No bounds checking is done.
   * The point is assume to lie within the image buffer.
   *
   * ImageFunction::IsInsideBuffer() can be used to check bounds before
   * calling the method. */
  OutputType
  EvaluateAtIndex(const IndexType & index) const override
  {
    OutputType output;
    PixelType  input = this->GetInputImage()->GetPixel(index);

    for (unsigned int k = 0; k < this->GetInputImage()->GetNumberOfComponentsPerPixel(); ++k)
    {
      output[k] = static_cast<double>(input[k]);
    }
    return (output);
  }

protected:
  VectorInterpolateImageFunction() = default;
  ~VectorInterpolateImageFunction() override = default;
};
} // end namespace itk

#endif