/*=========================================================================
 *
 *  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 "itkOneWayEquivalencyTable.h"

namespace itk
{
bool
OneWayEquivalencyTable::Add(unsigned long a, unsigned long b)
{
  //
  // Unlike EquivalencyTable, the order of the equivalence is important.
  //
  std::pair<Iterator, bool> result;
  if (a == b)
  {
    return false;
  }
  result = m_HashMap.insert(ValueType(a, b));

  return result.second;
}

// void OneWayEquivalencyTable::PrintHashTable()
//{
//  ConstIterator it = this->Begin();
//  while (it != this->End() )
//    {
//      std::cout << it->first << " = " << it->second << std::endl;
//      ++it;
//    }
//}

void
OneWayEquivalencyTable::Flatten()
{
  auto it = this->Begin();

  while (it != this->End())
  {
    it->second = this->RecursiveLookup(it->first);
    ++it;
  }
}

unsigned long
OneWayEquivalencyTable::RecursiveLookup(const unsigned long a) const
{
  unsigned long ans = a;
  unsigned long last_ans = a;

  ConstIterator it;
  auto          hashEnd = m_HashMap.end();

  while ((it = m_HashMap.find(ans)) != hashEnd)
  {
    ans = it->second;
    if (ans == a)
    {
      return last_ans; // about to cycle again.
    }
    last_ans = ans;
  }

  return ans;
}

void
OneWayEquivalencyTable::PrintSelf(std::ostream & os, Indent indent) const
{
  Superclass::PrintSelf(os, indent);
}
} // end namespace itk
