/*
 * Copyright (C) 2011 Apple 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:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. 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.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS 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 APPLE INC. OR ITS 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, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
 * THE POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef DoublyLinkedList_h
#define DoublyLinkedList_h

namespace WTF {

template <typename Node> class DoublyLinkedList {
public:
    DoublyLinkedList();
    
    bool isEmpty();

    Node* head();

    void append(Node*);
    void remove(Node*);

private:
    Node* m_head;
    Node* m_tail;
};

template <typename Node> inline DoublyLinkedList<Node>::DoublyLinkedList()
    : m_head(0)
    , m_tail(0)
{
}

template <typename Node> inline bool DoublyLinkedList<Node>::isEmpty()
{
    return !m_head;
}

template <typename Node> inline Node* DoublyLinkedList<Node>::head()
{
    return m_head;
}

template <typename Node> inline void DoublyLinkedList<Node>::append(Node* node)
{
    if (!m_tail) {
        ASSERT(!m_head);
        m_head = node;
        m_tail = node;
        node->setPrev(0);
        node->setNext(0);
        return;
    }

    ASSERT(m_head);
    m_tail->setNext(node);
    node->setPrev(m_tail);
    node->setNext(0);
    m_tail = node;
}

template <typename Node> inline void DoublyLinkedList<Node>::remove(Node* node)
{
    if (node->prev()) {
        ASSERT(node != m_head);
        node->prev()->setNext(node->next());
    } else {
        ASSERT(node == m_head);
        m_head = node->next();
    }

    if (node->next()) {
        ASSERT(node != m_tail);
        node->next()->setPrev(node->prev());
    } else {
        ASSERT(node == m_tail);
        m_tail = node->prev();
    }
}

} // namespace WTF

using WTF::DoublyLinkedList;

#endif