/*

 *  This file is part of the KDE libraries

 *  Copyright (C) 2003 Apple Computer, Inc.

 *

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

 *  modify it under the terms of the GNU Library General Public

 *  License as published by the Free Software Foundation; either

 *  version 2 of the License, or (at your option) any later version.

 *

 *  This library 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

 *  Library General Public License for more details.

 *

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

 *  along with this library; see the file COPYING.LIB.  If not, write to

 *  the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,

 *  Boston, MA 02110-1301, USA.

 *

 */

#ifndef KJS_SCOPE_CHAIN_H

#define KJS_SCOPE_CHAIN_H

#include <assert.h>

namespace KJS {

    class JSObject;

    class ExecState;

    class ScopeChainNode {

    public:

        ScopeChainNode(ScopeChainNode *n, JSObject *o)

            : next(n), object(o), refCount(1) { }

        ScopeChainNode *next;

        JSObject *object;

        int refCount;

    };

    class ScopeChainIterator {

    public:

        ScopeChainIterator(ScopeChainNode *node) : m_node(node) {}

        JSObject * const & operator*() const { return m_node->object; }

        JSObject * const * operator->() const { return &(operator*()); }

        ScopeChainIterator& operator++() { m_node = m_node->next; return *this; }

        // postfix ++ intentionally omitted

        bool operator==(const ScopeChainIterator& other) const { return m_node == other.m_node; }

        bool operator!=(const ScopeChainIterator& other) const { return m_node != other.m_node; }

    private:

        ScopeChainNode *m_node;

    };

    class ScopeChain {

    public:

        ScopeChain() : _node(0) { }

        ~ScopeChain() { deref(); }

        ScopeChain(const ScopeChain &c) : _node(c._node)

            { if (_node) ++_node->refCount; }

        ScopeChain &operator=(const ScopeChain &);

        bool isEmpty() const { return !_node; }

        JSObject *top() const { return _node->object; }

        JSObject *bottom() const;

        ScopeChainIterator begin() const { return ScopeChainIterator(_node); }

        ScopeChainIterator end() const { return ScopeChainIterator(0); }

        void clear() { deref(); _node = 0; }

        void push(JSObject *);

        void push(const ScopeChain &);

        void pop();

        void mark();

#ifndef NDEBUG        

        void print();

#endif

    private:

        ScopeChainNode *_node;

        void deref() { if (_node && --_node->refCount == 0) release(); }

        void ref() const;

        void release();

    };

inline void ScopeChain::ref() const

{

    for (ScopeChainNode *n = _node; n; n = n->next) {

        if (n->refCount++ != 0)

            break;

    }

}

inline ScopeChain &ScopeChain::operator=(const ScopeChain &c)

{

    c.ref();

    deref();

    _node = c._node;

    return *this;

}

inline JSObject *ScopeChain::bottom() const

{

    ScopeChainNode *last = 0;

    for (ScopeChainNode *n = _node; n; n = n->next)

        last = n;

    if (!last)

        return 0;

    return last->object;

}

inline void ScopeChain::push(JSObject *o)

{

    assert(o);

    _node = new ScopeChainNode(_node, o);

}

inline void ScopeChain::pop()

{

    ScopeChainNode *oldNode = _node;

    assert(oldNode);

    ScopeChainNode *newNode = oldNode->next;

    _node = newNode;

    if (--oldNode->refCount != 0) {

        if (newNode)

            ++newNode->refCount;

    } else {

        delete oldNode;

    }

}

} // namespace KJS

#endif // KJS_SCOPE_CHAIN_H