/*

 * Copyright (c) 2016, 2018, 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

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 */

#ifndef SHARE_VM_JFR_UTILITIES_JFRLISTITERATOR_HPP

#define SHARE_VM_JFR_UTILITIES_JFRLISTITERATOR_HPP

#include "memory/allocation.hpp"

enum jfr_iter_direction {

  forward = 1,

  backward

};

template <typename Node>

class StopOnNullCondition : public AllStatic {

 public:

  static bool has_next(const Node* node) {

    return node != NULL;

  }

};

template <typename List, template <typename> class ContinuationPredicate>

class Navigator {

 public:

  typedef typename List::Node Node;

  typedef jfr_iter_direction Direction;

  Navigator(List& list, Direction direction) :

    _list(list), _node(direction == forward ? list.head() : list.tail()), _direction(direction) {}

  bool has_next() const {

    return ContinuationPredicate<Node>::has_next(_node);

  }

  bool direction_forward() const {

    return _direction == forward;

  }

  Node* next() const {

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

    Node* temp = _node;

    _node = direction_forward() ? (Node*)_node->next() : (Node*)_node->prev();

    return temp;

  }

  void set_direction(Direction direction) {

    _direction = direction;

  }

  void reset(Direction direction) {

    set_direction(direction);

    _node = direction_forward() ? _list.head() : _list.tail();

  }

 private:

  List& _list;

  mutable Node* _node;

  Direction _direction;

};

template <typename List>

class NavigatorStopOnNull : public Navigator<List, StopOnNullCondition> {

 public:

  NavigatorStopOnNull(List& list, jfr_iter_direction direction = forward) : Navigator<List, StopOnNullCondition>(list, direction) {}

};

template<typename List, template <typename> class Navigator, typename AP = StackObj>

class IteratorHost : public AP {

 private:

  Navigator<List> _navigator;

 public:

  typedef typename List::Node Node;

  typedef jfr_iter_direction Direction;

  IteratorHost(List& list, Direction direction = forward) : AP(), _navigator(list, direction) {}

  void reset(Direction direction = forward) { _navigator.reset(direction); }

  bool has_next() const { return _navigator.has_next(); }

  Node* next() const { return _navigator.next(); }

  void set_direction(Direction direction) { _navigator.set_direction(direction); }

};

template<typename List, typename AP = StackObj>

class StopOnNullIterator : public IteratorHost<List, NavigatorStopOnNull, AP> {

 public:

  StopOnNullIterator(List& list, jfr_iter_direction direction = forward) : IteratorHost<List, NavigatorStopOnNull, AP>(list, direction) {}

};

#endif // SHARE_VM_JFR_UTILITIES_JFRLISTITERATOR_HPP