/*

 * Copyright (c) 2016, 2019, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

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 */

#ifndef SHARE_JFR_UTILITIES_JFRDOUBLYLINKEDLIST_HPP

#define SHARE_JFR_UTILITIES_JFRDOUBLYLINKEDLIST_HPP

#include "memory/allocation.hpp"

template <typename T>

class JfrDoublyLinkedList {

 private:

  T* _head;

  T* _tail;

  size_t _count;

  T** list_head() { return &_head; }

  T** list_tail() { return &_tail; }

 public:

  typedef T Node;

  JfrDoublyLinkedList() : _head(NULL), _tail(NULL), _count(0) {}

  T* head() const { return _head; }

  T* tail() const { return _tail; }

  size_t count() const { return _count; }

  T* clear(bool return_tail = false);

  T* remove(T* const node);

  void prepend(T* const node);

  void append(T* const node);

  void append_list(T* const head_node, T* const tail_node, size_t count);

};

template <typename T>

inline void JfrDoublyLinkedList<T>::prepend(T* const node) {

  assert(node != NULL, "invariant");

  node->set_prev(NULL);

  assert(!in_list(node), "already in list error");

  T** lh = list_head();

  if (*lh != NULL) {

    (*lh)->set_prev(node);

    node->set_next(*lh);

  } else {

    T** lt = list_tail();

    assert(*lt == NULL, "invariant");

    *lt = node;

    node->set_next(NULL);

    assert(tail() == node, "invariant");

    assert(node->next() == NULL, "invariant");

  }

  *lh = node;

  ++_count;

  assert(head() == node, "head error");

  assert(in_list(node), "not in list error");

  assert(node->prev() == NULL, "invariant");

}

template <typename T>

void JfrDoublyLinkedList<T>::append(T* const node) {

  assert(node != NULL, "invariant");

  node->set_next(NULL);

  assert(!in_list(node), "already in list error");

  T** lt = list_tail();

  if (*lt != NULL) {

    // already an existing tail

    node->set_prev(*lt);

    (*lt)->set_next(node);

  } else {

    // if no tail, also update head

    assert(*lt == NULL, "invariant");

    T** lh = list_head();

    assert(*lh == NULL, "invariant");

    node->set_prev(NULL);

    *lh = node;

    assert(head() == node, "invariant");

  }

  *lt = node;

  ++_count;

  assert(tail() == node, "invariant");

  assert(in_list(node), "not in list error");

  assert(node->next() == NULL, "invariant");

}

template <typename T>

T* JfrDoublyLinkedList<T>::remove(T* const node) {

  assert(node != NULL, "invariant");

  assert(in_list(node), "invariant");

  T* const prev = (T*)node->prev();

  T* const next = (T*)node->next();

  if (prev == NULL) {

    assert(head() == node, "head error");

    if (next != NULL) {

      next->set_prev(NULL);

    } else {

      assert(next == NULL, "invariant");

      assert(tail() == node, "tail error");

      T** lt = list_tail();

      *lt = NULL;

      assert(tail() == NULL, "invariant");

    }

    T** lh = list_head();

    *lh = next;

    assert(head() == next, "invariant");

  } else {

    assert(prev != NULL, "invariant");

    if (next == NULL) {

      assert(tail() == node, "tail error");

      T** lt = list_tail();

      *lt = prev;

      assert(tail() == prev, "invariant");

    } else {

       next->set_prev(prev);

    }

    prev->set_next(next);

  }

  --_count;

  assert(_count >= 0, "invariant");

  assert(!in_list(node), "still in list error");

  return node;

}

template <typename T>

T* JfrDoublyLinkedList<T>::clear(bool return_tail /* false */) {

  T* const node = return_tail ? tail() : head();

  T** l = list_head();

  *l = NULL;

  l = list_tail();

  *l = NULL;

  _count = 0;

  assert(head() == NULL, "invariant");

  assert(tail() == NULL, "invariant");

  return node;

}

template <typename T>

bool JfrDoublyLinkedList<T>::locate(const T* node, const T* const target) const {

  assert(target != NULL, "invariant");

  while (node != NULL) {

    if (node == target) {

      return true;

    }

    node = (T*)node->next();

  }

  return false;

}

template <typename T>

bool JfrDoublyLinkedList<T>::in_list(const T* const target) const {

  assert(target != NULL, "invariant");

  return locate(head(), target);

}

template <typename T>

inline void validate_count_param(T* node, size_t count_param) {

  assert(node != NULL, "invariant");

  size_t count = 0;

  while (node) {

    ++count;

    node = (T*)node->next();

  }

  assert(count_param == count, "invariant");

}

template <typename T>

void JfrDoublyLinkedList<T>::append_list(T* const head_node, T* const tail_node, size_t count) {

  assert(head_node != NULL, "invariant");

  assert(!in_list(head_node), "already in list error");

  assert(tail_node != NULL, "invariant");

  assert(!in_list(tail_node), "already in list error");

  assert(tail_node->next() == NULL, "invariant");

  // ensure passed in list nodes are connected

  assert(locate(head_node, tail_node), "invariant");

  T** lt = list_tail();

  if (*lt != NULL) {

    head_node->set_prev(*lt);

    (*lt)->set_next(head_node);

  } else {

    // no head

    assert(*lt == NULL, "invariant");

    T** lh = list_head();

    assert(*lh == NULL, "invariant");

    head_node->set_prev(NULL);

    *lh = head_node;

    assert(head() == head_node, "invariant");

  }

  *lt = tail_node;

  const T* node = head_node;

  debug_only(validate_count_param(node, count);)

    _count += count;

  assert(tail() == tail_node, "invariant");

  assert(in_list(tail_node), "not in list error");

  assert(in_list(head_node), "not in list error");

}

#endif // SHARE_JFR_UTILITIES_JFRDOUBLYLINKEDLIST_HPP