#ifndef _QUEUE_HPP
#define _QUEUE_HPP

template<class Item>
class QueueIterator;


template<class Item>
class Queue {
public:
        Queue() : firstIterator(0) {}
        virtual ~Queue() {}

        virtual void put(const Item &i) =0;
        virtual Item get() =0;
        virtual Item peek() const =0;
        virtual void clear() =0;

        virtual int isEmpty() const =0;
        virtual unsigned length() const =0;
        virtual const Item& itemAt(unsigned at) const =0;

private:
        QueueIterator<Item> *firstIterator;
protected:
        void cleared();
        void itemInserted(unsigned before);
        void itemAppended(unsigned after);
        void itemRemoved(unsigned at, unsigned ql);

        friend class QueueIterator<Item>;
        class QLock {
                Queue<Item> *q;
        public: QLock(const Queue<Item> *queue) : q((Queue<Item>*)queue) { q->lock(); }
                ~QLock() { q->unlock(); }
        };

        friend class QLock;
        virtual lock() {}
        virtual unlock() {}
};

template<class Item>
class QueueIterator {
        QueueIterator(const QueueIterator<Item>&);     //dont copy
        operator=(const QueueIterator<Item>&);         //dont copy
public:
        QueueIterator(const Queue<Item> &queue);
        virtual ~QueueIterator();

        virtual int isDone();
        virtual const Item* currentItem();
        virtual int advance();
        virtual void reset();

private:
        QueueIterator<Item> *prev,*next;
        const Queue<Item> &q;
        int currentIndex,nextIndex;

        friend class Queue<Item>;
        void queueCleared();
        void queueItemInserted(unsigned before);
        void queueItemAppended(unsigned after);
        void queueItemRemoved(unsigned at, unsigned ql);
};

#include "queue.cpp"

#endif