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

namespace itk::Statistics
{
MaximumRatioDecisionRule::MaximumRatioDecisionRule() = default;

void
MaximumRatioDecisionRule::PrintSelf(std::ostream & os, Indent indent) const
{
  Superclass::PrintSelf(os, indent);

  os << "Prior probabilities: ";
  PriorProbabilityVectorType::size_type N = 10;
  if (m_PriorProbabilities.size() < N)
  {
    N = m_PriorProbabilities.size();
  }
  os << '[' << std::endl;
  for (PriorProbabilityVectorType::size_type i = 0; i < N; ++i)
  {
    os << m_PriorProbabilities[i];
    if (i + 1 < N)
    {
      os << ", ";
    }
  }
  if (!m_PriorProbabilities.empty() && m_PriorProbabilities.size() < N)
  {
    os << ", ...";
  }
  os << ']' << std::endl;
}

void
MaximumRatioDecisionRule::SetPriorProbabilities(const PriorProbabilityVectorType & p)
{
  if (p.size() != m_PriorProbabilities.size())
  {
    m_PriorProbabilities = p;
    this->Modified();
  }
  else
  {
    auto pit = p.begin();
    for (auto it = m_PriorProbabilities.begin(); pit != p.end(); ++pit, ++it)
    {
      if (itk::Math::Absolute(*pit - *it) > itk::Math::eps)
      {
        break;
      }
    }
    if (pit != p.end())
    {
      m_PriorProbabilities = p;
      this->Modified();
    }
  }
}

MaximumRatioDecisionRule::ClassIdentifierType
MaximumRatioDecisionRule::Evaluate(const MembershipVectorType & discriminantScores) const
{
  bool uniformPrior = false;
  if (discriminantScores.size() != m_PriorProbabilities.size())
  {
    itkWarningMacro("Size mismatch between discriminant scores (" << discriminantScores.size() << ") and priors ("
                                                                  << m_PriorProbabilities.size()
                                                                  << "). Reverting to a uniform prior.");
    uniformPrior = true;
  }

  if (uniformPrior)
  {
    // find the maximum discriminant score. if list is empty, return 0.
    ClassIdentifierType besti = 0;
    MembershipValueType best = NumericTraits<MembershipValueType>::NonpositiveMin();
    for (ClassIdentifierType i = 0; i < discriminantScores.size(); ++i)
    {
      if (discriminantScores[i] > best)
      {
        best = discriminantScores[i];
        besti = i;
      }
    }
    return besti;
  }

  // Non-uniform prior case
  // find the maximum p(x|i)*p(i)
  ClassIdentifierType besti = 0;
  MembershipValueType best = NumericTraits<MembershipValueType>::NonpositiveMin();
  for (ClassIdentifierType i = 0; i < discriminantScores.size(); ++i)
  {
    const MembershipValueType temp = discriminantScores[i] * m_PriorProbabilities[i];
    if (temp > best)
    {
      best = temp;
      besti = i;
    }
  }
  return besti;
}
} // namespace itk::Statistics
