/*=========================================================================
 *
 *  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 itkObjectToObjectMultiMetricv4_hxx
#define itkObjectToObjectMultiMetricv4_hxx

#include "itkCompositeTransform.h"

namespace itk
{

template <unsigned int TFixedDimension,
          unsigned int TMovingDimension,
          typename TVirtualImage,
          typename TInternalComputationValueType>
ObjectToObjectMultiMetricv4<TFixedDimension, TMovingDimension, TVirtualImage, TInternalComputationValueType>::
  ObjectToObjectMultiMetricv4()
{
  this->m_MetricQueue.clear();

  // We want the moving transform to be nullptr by default
  this->m_MovingTransform = nullptr;
}

template <unsigned int TFixedDimension,
          unsigned int TMovingDimension,
          typename TVirtualImage,
          typename TInternalComputationValueType>
void
ObjectToObjectMultiMetricv4<TFixedDimension, TMovingDimension, TVirtualImage, TInternalComputationValueType>::AddMetric(
  MetricType * metric)
{
  this->m_MetricQueue.push_back(metric);
}

template <unsigned int TFixedDimension,
          unsigned int TMovingDimension,
          typename TVirtualImage,
          typename TInternalComputationValueType>
void
ObjectToObjectMultiMetricv4<TFixedDimension, TMovingDimension, TVirtualImage, TInternalComputationValueType>::
  ClearMetricQueue()
{
  this->m_MetricQueue.clear();
}

template <unsigned int TFixedDimension,
          unsigned int TMovingDimension,
          typename TVirtualImage,
          typename TInternalComputationValueType>
itk::SizeValueType
ObjectToObjectMultiMetricv4<TFixedDimension, TMovingDimension, TVirtualImage, TInternalComputationValueType>::
  GetNumberOfMetrics() const
{
  return static_cast<itk::SizeValueType>(this->m_MetricQueue.size());
}

template <unsigned int TFixedDimension,
          unsigned int TMovingDimension,
          typename TVirtualImage,
          typename TInternalComputationValueType>
void
ObjectToObjectMultiMetricv4<TFixedDimension, TMovingDimension, TVirtualImage, TInternalComputationValueType>::
  SetMovingTransform(MovingTransformType * transform)
{
  if (this->GetNumberOfMetrics() == 0)
  {
    itkExceptionMacro("No metrics are assigned. Cannot assign transform.");
  }
  Superclass::SetMovingTransform(transform);
  for (SizeValueType j = 0; j < this->GetNumberOfMetrics(); ++j)
  {
    this->m_MetricQueue[j]->SetMovingTransform(transform);
  }
}

template <unsigned int TFixedDimension,
          unsigned int TMovingDimension,
          typename TVirtualImage,
          typename TInternalComputationValueType>
void
ObjectToObjectMultiMetricv4<TFixedDimension, TMovingDimension, TVirtualImage, TInternalComputationValueType>::
  SetFixedTransform(FixedTransformType * transform)
{
  if (this->GetNumberOfMetrics() == 0)
  {
    itkExceptionMacro("No metrics are assigned. Cannot assign transform.");
  }
  Superclass::SetFixedTransform(transform);
  for (SizeValueType j = 0; j < this->GetNumberOfMetrics(); ++j)
  {
    this->m_MetricQueue[j]->SetFixedTransform(transform);
  }
}

template <unsigned int TFixedDimension,
          unsigned int TMovingDimension,
          typename TVirtualImage,
          typename TInternalComputationValueType>
void
ObjectToObjectMultiMetricv4<TFixedDimension, TMovingDimension, TVirtualImage, TInternalComputationValueType>::
  Initialize()
{
  if (this->GetNumberOfMetrics() == 0)
  {
    itkExceptionMacro("No metrics are assigned. Cannot evaluate.");
  }

  /* Verify derivative weights and initialize if appropriate */
  if (this->m_MetricWeights.Size() > 0)
  {
    if (this->m_MetricWeights.Size() != this->GetNumberOfMetrics())
    {
      itkExceptionMacro("The derivative weights are not of the proper size. "
                        "Number of metrics: "
                        << this->GetNumberOfMetrics()
                        << ", "
                           "Number of weights: "
                        << this->m_MetricWeights.Size());
    }
    /* normalize the weights */
    WeightValueType sum{};
    for (SizeValueType j = 0; j < this->GetNumberOfMetrics(); ++j)
    {
      sum += this->m_MetricWeights[j];
    }
    if (sum <= NumericTraits<WeightValueType>::epsilon())
    {
      itkExceptionMacro("The derivative weights are too small: " << this->m_MetricWeights);
    }
    for (SizeValueType j = 0; j < this->GetNumberOfMetrics(); ++j)
    {
      this->m_MetricWeights[j] = this->m_MetricWeights[j] / sum;
    }
  }
  else
  {
    /* Initialize to defaults */
    this->m_MetricWeights.SetSize(this->GetNumberOfMetrics());
    this->m_MetricWeights.Fill(NumericTraits<WeightValueType>::OneValue() /
                               static_cast<WeightValueType>(this->GetNumberOfMetrics()));
  }

  /* resize */
  this->m_MetricValueArray.SetSize(this->GetNumberOfMetrics());

  /* Verify the same transform is in all metrics. */
  const MovingTransformType * firstTransform = nullptr;
  for (SizeValueType j = 0; j < this->GetNumberOfMetrics(); ++j)
  {
    const MovingTransformType * transform = this->m_MetricQueue[j]->GetMovingTransform();
    // Check if it's a composite. If so, there must be only one transform set to be
    // optimized, and it must be the same as in other metrics.
    using CompositeType = CompositeTransform<typename MovingTransformType::ScalarType, TFixedDimension>;
    const auto * composite = dynamic_cast<const CompositeType *>(transform);
    if (composite != nullptr)
    {
      SizeValueType count = 0;
      for (size_t n = 0; n < composite->GetNumberOfTransforms(); ++n)
      {
        if (composite->GetNthTransformToOptimize(static_cast<SizeValueType>(n)))
        {
          ++count;
          transform = composite->GetNthTransformConstPointer(static_cast<SizeValueType>(n));
        }
      }
      if (count != 1)
      {
        itkExceptionMacro(
          "Expected exactly one transform set to be optimized within the composite transform. Error with metric "
          << j << '.');
      }
    }

    if (j == 0)
    {
      firstTransform = transform;
    }
    else
    {
      if (transform != firstTransform)
      {
        itkExceptionMacro("One or more component metrics have different active transforms. "
                          "Each metric must be using the same transform object. For CompositeTransform, "
                          "there must be only one transform set to optimize, and it must be the same "
                          "as other metric transforms.");
      }
    }
  }

  /* Assign local pointers to common transforms */
  if (this->m_MovingTransform.IsNull())
  {
    Superclass::SetMovingTransform(const_cast<MovingTransformType *>(this->m_MetricQueue[0]->GetMovingTransform()));
  }
  if (this->m_FixedTransform.IsNull())
  {
    Superclass::SetFixedTransform(const_cast<MovingTransformType *>(this->m_MetricQueue[0]->GetFixedTransform()));
  }

  /* Initialize individual metrics. */
  for (SizeValueType j = 0; j < this->GetNumberOfMetrics(); ++j)
  {
    try
    {
      this->m_MetricQueue[j]->Initialize();
    }
    catch (const ExceptionObject & exc)
    {
      std::string msg("Caught exception initializing metric: \n");
      msg += exc.what();
      ExceptionObject err(__FILE__, __LINE__, msg);
      throw err;
    }
  }

  /* Get the first valid virtual domain and assign
   * it to this metric as a common virtual domain,
   * for direct use by calling classes. */
  for (SizeValueType j = 0; j < this->GetNumberOfMetrics(); ++j)
  {
    if (this->m_MetricQueue[j]->GetVirtualImage())
    {
      this->SetVirtualDomainFromImage(this->m_MetricQueue[j]->GetVirtualImage());
      break;
    }
  }

  /* Do this after we've setup local copy of virtual domain */
  Superclass::Initialize();
}

template <unsigned int TFixedDimension,
          unsigned int TMovingDimension,
          typename TVirtualImage,
          typename TInternalComputationValueType>
typename ObjectToObjectMultiMetricv4<TFixedDimension,
                                     TMovingDimension,
                                     TVirtualImage,
                                     TInternalComputationValueType>::MeasureType
ObjectToObjectMultiMetricv4<TFixedDimension, TMovingDimension, TVirtualImage, TInternalComputationValueType>::GetValue()
  const
{
  for (SizeValueType j = 0; j < this->GetNumberOfMetrics(); ++j)
  {
    this->m_MetricValueArray[j] = this->m_MetricQueue[j]->GetValue();
  }

  MeasureType firstValue = this->m_MetricValueArray[0];
  this->m_Value = firstValue;
  return firstValue;
}

template <unsigned int TFixedDimension,
          unsigned int TMovingDimension,
          typename TVirtualImage,
          typename TInternalComputationValueType>
void
ObjectToObjectMultiMetricv4<TFixedDimension, TMovingDimension, TVirtualImage, TInternalComputationValueType>::
  GetDerivative(DerivativeType & derivativeResult) const
{
  MeasureType firstValue;
  this->GetValueAndDerivative(firstValue, derivativeResult);
}

template <unsigned int TFixedDimension,
          unsigned int TMovingDimension,
          typename TVirtualImage,
          typename TInternalComputationValueType>
void
ObjectToObjectMultiMetricv4<TFixedDimension, TMovingDimension, TVirtualImage, TInternalComputationValueType>::
  GetValueAndDerivative(MeasureType & firstValue, DerivativeType & derivativeResult) const
{
  if (derivativeResult.GetSize() != this->GetNumberOfParameters())
  {
    derivativeResult.SetSize(this->GetNumberOfParameters());
  }
  derivativeResult.Fill(DerivativeValueType{});

  DerivativeType metricDerivative;
  MeasureType    metricValue{};

  // Loop over metrics
  DerivativeValueType totalMagnitude{};
  for (SizeValueType j = 0; j < this->GetNumberOfMetrics(); ++j)
  {
    this->m_MetricQueue[j]->GetValueAndDerivative(metricValue, metricDerivative);
    this->m_MetricValueArray[j] = metricValue;

    DerivativeValueType magnitude = metricDerivative.magnitude();
    DerivativeValueType weightOverMagnitude{};
    totalMagnitude += magnitude;

    if (magnitude > NumericTraits<DerivativeValueType>::epsilon())
    {
      weightOverMagnitude = this->m_MetricWeights[j] / magnitude;
    }
    // derivative = \sum_j w_j * (dM_j / ||dM_j||)
    for (NumberOfParametersType p = 0; p < this->GetNumberOfParameters(); ++p)
    {
      // roll our own loop to avoid temporary variable that could be large when using displacement fields.
      derivativeResult[p] += (metricDerivative[p] * weightOverMagnitude);
    }
  }

  // Scale by totalMagnitude to prevent what amounts to implicit step estimation from magnitude scaling.
  // This keeps the behavior of this metric the same as a regular metric, with respect to derivative
  // magnitudes.
  totalMagnitude /= this->GetNumberOfMetrics();
  for (NumberOfParametersType p = 0; p < this->GetNumberOfParameters(); ++p)
  {
    derivativeResult[p] *= totalMagnitude;
  }

  firstValue = this->m_MetricValueArray[0];
  this->m_Value = firstValue;
}

template <unsigned int TFixedDimension,
          unsigned int TMovingDimension,
          typename TVirtualImage,
          typename TInternalComputationValueType>
typename ObjectToObjectMultiMetricv4<TFixedDimension, TMovingDimension, TVirtualImage, TInternalComputationValueType>::
  MetricValueArrayType
  ObjectToObjectMultiMetricv4<TFixedDimension, TMovingDimension, TVirtualImage, TInternalComputationValueType>::
    GetValueArray() const
{
  return this->m_MetricValueArray;
}

template <unsigned int TFixedDimension,
          unsigned int TMovingDimension,
          typename TVirtualImage,
          typename TInternalComputationValueType>
typename ObjectToObjectMultiMetricv4<TFixedDimension, TMovingDimension, TVirtualImage, TInternalComputationValueType>::
  MeasureType
  ObjectToObjectMultiMetricv4<TFixedDimension, TMovingDimension, TVirtualImage, TInternalComputationValueType>::
    GetWeightedValue() const
{
  MeasureType value{};

  for (SizeValueType j = 0; j < this->GetNumberOfMetrics(); ++j)
  {
    // value = sum_j w_j * M_j
    value += this->m_MetricValueArray[j] * this->m_MetricWeights[j];
  }
  return value;
}

template <unsigned int TFixedDimension,
          unsigned int TMovingDimension,
          typename TVirtualImage,
          typename TInternalComputationValueType>
const typename ObjectToObjectMultiMetricv4<TFixedDimension,
                                           TMovingDimension,
                                           TVirtualImage,
                                           TInternalComputationValueType>::MetricQueueType &
ObjectToObjectMultiMetricv4<TFixedDimension, TMovingDimension, TVirtualImage, TInternalComputationValueType>::
  GetMetricQueue() const
{
  return this->m_MetricQueue;
}


template <unsigned int TFixedDimension,
          unsigned int TMovingDimension,
          typename TVirtualImage,
          typename TInternalComputationValueType>
bool
ObjectToObjectMultiMetricv4<TFixedDimension, TMovingDimension, TVirtualImage, TInternalComputationValueType>::
  SupportsArbitraryVirtualDomainSamples() const
{
  for (SizeValueType j = 0; j < this->GetNumberOfMetrics(); ++j)
  {
    if (!this->m_MetricQueue[j]->SupportsArbitraryVirtualDomainSamples())
    {
      return false;
    }
  }
  return true;
}

template <unsigned int TFixedDimension,
          unsigned int TMovingDimension,
          typename TVirtualImage,
          typename TInternalComputationValueType>
void
ObjectToObjectMultiMetricv4<TFixedDimension, TMovingDimension, TVirtualImage, TInternalComputationValueType>::PrintSelf(
  std::ostream & os,
  Indent         indent) const
{
  os << indent << "Weights of metric derivatives: " << this->m_MetricWeights << std::endl;
  os << indent << "The multivariate contains the following metrics: " << std::endl << std::endl;
  for (SizeValueType i = 0; i < this->GetNumberOfMetrics(); ++i)
  {
    os << indent << "~~~ Metric " << i << " ~~~" << std::endl;
    this->m_MetricQueue[i]->Print(os, indent.GetNextIndent());
  }
}

} // end namespace itk

#endif // itkObjectToObjectMultiMetricv4_hxx
