/*
 * Copyright (C) 2013 Google Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above
 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
 *     * Neither the name of Google Inc. nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef TreeNode_h
#define TreeNode_h

#include "wtf/Assertions.h"

namespace WTF {

//
// TreeNode is generic, ContainerNode-like linked tree data structure.
// There are a few notable difference between TreeNode and Node:
//
//  * Each TreeNode node is NOT ref counted. The user have to retain its
//    lifetime somehow.
//    FIXME: lifetime management could be parameterized so that ref counted
//    implementations can be used.
//  * It ASSERT()s invalid input. The callers have to ensure that given
//    parameter is sound.
//  * There is no branch-leaf difference. Every node can be a parent of other
//    node.
//
// FIXME: oilpan: Trace tree node edges to ensure we don't have dangling
// pointers.
// As it is used in HTMLImport it is safe since they all die together.
template <class T>
class TreeNode {
 public:
  typedef T NodeType;

  TreeNode()
      : m_next(0),
        m_previous(0),
        m_parent(0),
        m_firstChild(0),
        m_lastChild(0) {}

  NodeType* next() const { return m_next; }
  NodeType* previous() const { return m_previous; }
  NodeType* parent() const { return m_parent; }
  NodeType* firstChild() const { return m_firstChild; }
  NodeType* lastChild() const { return m_lastChild; }
  NodeType* here() const {
    return static_cast<NodeType*>(const_cast<TreeNode*>(this));
  }

  bool orphan() const {
    return !m_parent && !m_next && !m_previous && !m_firstChild && !m_lastChild;
  }
  bool hasChildren() const { return m_firstChild; }

  void insertBefore(NodeType* newChild, NodeType* refChild) {
    ASSERT(!newChild->parent());
    ASSERT(!newChild->next());
    ASSERT(!newChild->previous());

    ASSERT(!refChild || this == refChild->parent());

    if (!refChild) {
      appendChild(newChild);
      return;
    }

    NodeType* newPrevious = refChild->previous();
    newChild->m_parent = here();
    newChild->m_next = refChild;
    newChild->m_previous = newPrevious;
    refChild->m_previous = newChild;
    if (newPrevious)
      newPrevious->m_next = newChild;
    else
      m_firstChild = newChild;
  }

  void appendChild(NodeType* child) {
    ASSERT(!child->parent());
    ASSERT(!child->next());
    ASSERT(!child->previous());

    child->m_parent = here();

    if (!m_lastChild) {
      ASSERT(!m_firstChild);
      m_lastChild = m_firstChild = child;
      return;
    }

    ASSERT(!m_lastChild->m_next);
    NodeType* oldLast = m_lastChild;
    m_lastChild = child;

    child->m_previous = oldLast;
    oldLast->m_next = child;
  }

  NodeType* removeChild(NodeType* child) {
    ASSERT(child->parent() == this);

    if (m_firstChild == child)
      m_firstChild = child->next();
    if (m_lastChild == child)
      m_lastChild = child->previous();

    NodeType* oldNext = child->next();
    NodeType* oldPrevious = child->previous();
    child->m_parent = child->m_next = child->m_previous = 0;

    if (oldNext)
      oldNext->m_previous = oldPrevious;
    if (oldPrevious)
      oldPrevious->m_next = oldNext;

    return child;
  }

  void takeChildrenFrom(NodeType* oldParent) {
    ASSERT(oldParent != this);
    while (oldParent->hasChildren()) {
      NodeType* child = oldParent->firstChild();
      oldParent->removeChild(child);
      this->appendChild(child);
    }
  }

 private:
  NodeType* m_next;
  NodeType* m_previous;
  NodeType* m_parent;
  NodeType* m_firstChild;
  NodeType* m_lastChild;
};

template <class T>
inline typename TreeNode<T>::NodeType* traverseNext(
    const TreeNode<T>* current,
    const TreeNode<T>* stayWithin = 0) {
  if (typename TreeNode<T>::NodeType* next = current->firstChild())
    return next;
  if (current == stayWithin)
    return 0;
  if (typename TreeNode<T>::NodeType* next = current->next())
    return next;
  for (typename TreeNode<T>::NodeType* parent = current->parent(); parent;
       parent = parent->parent()) {
    if (parent == stayWithin)
      return 0;
    if (typename TreeNode<T>::NodeType* next = parent->next())
      return next;
  }

  return 0;
}

template <class T>
inline typename TreeNode<T>::NodeType* traverseFirstPostOrder(
    const TreeNode<T>* current) {
  typename TreeNode<T>::NodeType* first = current->here();
  while (first->firstChild())
    first = first->firstChild();
  return first;
}

template <class T>
inline typename TreeNode<T>::NodeType* traverseNextPostOrder(
    const TreeNode<T>* current,
    const TreeNode<T>* stayWithin = 0) {
  if (current == stayWithin)
    return 0;

  typename TreeNode<T>::NodeType* next = current->next();
  if (!next)
    return current->parent();
  while (next->firstChild())
    next = next->firstChild();
  return next;
}

}  // namespace WTF

using WTF::TreeNode;
using WTF::traverseNext;
using WTF::traverseNextPostOrder;

#endif