/*=========================================================================
 *
 *  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 itkLeafTreeIterator_h
#define itkLeafTreeIterator_h

#include "itkPreOrderTreeIterator.h"

namespace itk
{
template <typename TTreeType>
class ITK_TEMPLATE_EXPORT LeafTreeIterator : public TreeIteratorBase<TTreeType>
{
public:
  /** Typedefs */
  using Self = LeafTreeIterator;
  using Superclass = TreeIteratorBase<TTreeType>;
  using TreeType = TTreeType;
  using ValueType = typename TreeType::ValueType;
  using typename Superclass::TreeNodeType;
  using typename Superclass::NodeType;

  /** Constructor */
  LeafTreeIterator(const TreeType * tree);

  /** Constructor */
  LeafTreeIterator(TreeType * tree);

  /** Destructor */
  ~LeafTreeIterator() override;

  /** Return the type of iterator */
  NodeType
  GetType() const override;

  /** Clone function */
  TreeIteratorBase<TTreeType> *
  Clone() override;

protected:
  /** Return the next value */
  const ValueType &
  Next() override;

  /** Return true if the next value exists */
  bool
  HasNext() const override;

private:
  /** Find the next node */
  const TreeNodeType *
  FindNextNode() const;
};

/** Constructor */
template <typename TTreeType>
LeafTreeIterator<TTreeType>::LeafTreeIterator(const TTreeType * tree)
  : TreeIteratorBase<TTreeType>(tree, nullptr)
{
  this->m_Begin = const_cast<TreeNodeType *>(this->FindNextNode()); //
                                                                    //
                                                                    // Position
                                                                    // the
                                                                    //
                                                                    // iterator
                                                                    // to
                                                                    // the
                                                                    // first
                                                                    // leaf;
}

/** Constructor */
template <typename TTreeType>
LeafTreeIterator<TTreeType>::LeafTreeIterator(TTreeType * tree)
  : TreeIteratorBase<TTreeType>(tree, nullptr)
{
  this->m_Begin = const_cast<TreeNodeType *>(this->FindNextNode()); //
                                                                    //
                                                                    // Position
                                                                    // the
                                                                    //
                                                                    // iterator
                                                                    // to
                                                                    // the
                                                                    // first
                                                                    // leaf;
}

/** Destructor */
template <typename TTreeType>
LeafTreeIterator<TTreeType>::~LeafTreeIterator() = default;

/** Return the type of iterator */
template <typename TTreeType>
auto
LeafTreeIterator<TTreeType>::GetType() const -> NodeType
{
  return TreeIteratorBaseEnums::TreeIteratorBaseNode::LEAF;
}

/** Return true if the next value exists */
template <typename TTreeType>
bool
LeafTreeIterator<TTreeType>::HasNext() const
{
  if (this->m_Position == nullptr)
  {
    return false;
  }
  if (const_cast<TreeNodeType *>(FindNextNode()) != nullptr)
  {
    return true;
  }
  return false;
}

/** Return the next node */
template <typename TTreeType>
const typename LeafTreeIterator<TTreeType>::ValueType &
LeafTreeIterator<TTreeType>::Next()
{
  this->m_Position = const_cast<TreeNodeType *>(FindNextNode());
  if (this->m_Position == nullptr)
  {
    return this->m_Root->Get(); // value irrelevant, but we have to return something
  }
  return this->m_Position->Get();
}

/** Find the next node given the position */
template <typename TTreeType>
const typename LeafTreeIterator<TTreeType>::TreeNodeType *
LeafTreeIterator<TTreeType>::FindNextNode() const
{
  PreOrderTreeIterator<TTreeType> it(this->m_Tree, this->m_Position);
  it.m_Root = this->m_Root;
  ++it; // go next
  if (it.IsAtEnd())
  {
    return nullptr;
  }

  if (!it.HasChild())
  {
    return it.GetNode();
  }

  while (!it.IsAtEnd())
  {
    if (!it.HasChild())
    {
      return it.GetNode();
    }
    ++it;
  }

  return nullptr;
}

/** Clone function */
template <typename TTreeType>
TreeIteratorBase<TTreeType> *
LeafTreeIterator<TTreeType>::Clone()
{
  auto * clone = new LeafTreeIterator<TTreeType>(this->m_Tree);
  *clone = *this;
  return clone;
}
} // end namespace itk

#endif