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#ifndef __TBB__flow_graph_item_buffer_impl_H
#define __TBB__flow_graph_item_buffer_impl_H

#ifndef __TBB_flow_graph_H
#error Do not #include this internal file directly; use public TBB headers instead.
#endif

#include "tbb/internal/_flow_graph_types_impl.h"  // for aligned_pair

// in namespace tbb::flow::interfaceX (included in _flow_graph_node_impl.h)

    //! Expandable buffer of items.  The possible operations are push, pop,
    //* tests for empty and so forth.  No mutual exclusion is built in.
    //* objects are constructed into and explicitly-destroyed.  get_my_item gives
    // a read-only reference to the item in the buffer.  set_my_item may be called
    // with either an empty or occupied slot.

    using internal::aligned_pair;
    using internal::alignment_of;

namespace internal {

    template <typename T, typename A=cache_aligned_allocator<T> >
    class item_buffer {
    public:
        typedef T item_type;
        enum buffer_item_state { no_item=0, has_item=1, reserved_item=2 };
    protected:
        typedef size_t size_type;
        typedef typename aligned_pair<item_type, buffer_item_state>::type buffer_item_type;
        typedef typename A::template rebind<buffer_item_type>::other allocator_type;

        buffer_item_type *my_array;
        size_type my_array_size;
        static const size_type initial_buffer_size = 4;
        size_type my_head;
        size_type my_tail;

        bool buffer_empty() const { return my_head == my_tail; }

        buffer_item_type &item(size_type i) {
            __TBB_ASSERT(!(size_type(&(my_array[i&(my_array_size-1)].second))%alignment_of<buffer_item_state>::value),NULL);
            __TBB_ASSERT(!(size_type(&(my_array[i&(my_array_size-1)].first))%alignment_of<item_type>::value), NULL);
            return my_array[i & (my_array_size - 1) ];
        }

        const buffer_item_type &item(size_type i) const {
            __TBB_ASSERT(!(size_type(&(my_array[i&(my_array_size-1)].second))%alignment_of<buffer_item_state>::value), NULL);
            __TBB_ASSERT(!(size_type(&(my_array[i&(my_array_size-1)].first))%alignment_of<item_type>::value), NULL);
            return my_array[i & (my_array_size-1)];
        }

        bool my_item_valid(size_type i) const { return (i < my_tail) && (i >= my_head) && (item(i).second != no_item); }
        bool my_item_reserved(size_type i) const { return item(i).second == reserved_item; }

        // object management in buffer
        const item_type &get_my_item(size_t i) const {
            __TBB_ASSERT(my_item_valid(i),"attempt to get invalid item");
            item_type *itm = (tbb::internal::punned_cast<item_type *>(&(item(i).first)));
            return *(const item_type *)itm;
        }

        // may be called with an empty slot or a slot that has already been constructed into.
        void set_my_item(size_t i, const item_type &o) {
            if(item(i).second != no_item) {
                destroy_item(i);
            }
            new(&(item(i).first)) item_type(o);
            item(i).second = has_item;
        }

        // destructively-fetch an object from the buffer
        void fetch_item(size_t i, item_type &o) {
            __TBB_ASSERT(my_item_valid(i), "Trying to fetch an empty slot");
            o = get_my_item(i);  // could have std::move assign semantics
            destroy_item(i);
        }

        // move an existing item from one slot to another.  The moved-to slot must be unoccupied,
        // the moved-from slot must exist and not be reserved.  The after, from will be empty,
        // to will be occupied but not reserved
        void move_item(size_t to, size_t from) {
            __TBB_ASSERT(!my_item_valid(to), "Trying to move to a non-empty slot");
            __TBB_ASSERT(my_item_valid(from), "Trying to move from an empty slot");
            set_my_item(to, get_my_item(from));   // could have std::move semantics
            destroy_item(from);

        }

        // put an item in an empty slot.  Return true if successful, else false
        bool place_item(size_t here, const item_type &me) {
#if !TBB_DEPRECATED_SEQUENCER_DUPLICATES
            if(my_item_valid(here)) return false;
#endif
            set_my_item(here, me);
            return true;
        }

        // could be implemented with std::move semantics
        void swap_items(size_t i, size_t j) {
            __TBB_ASSERT(my_item_valid(i) && my_item_valid(j), "attempt to swap invalid item(s)");
            item_type temp = get_my_item(i);
            set_my_item(i, get_my_item(j));
            set_my_item(j, temp);
        }

        void destroy_item(size_type i) {
            __TBB_ASSERT(my_item_valid(i), "destruction of invalid item");
            (tbb::internal::punned_cast<item_type *>(&(item(i).first)))->~item_type();
            item(i).second = no_item;
        }

        // returns the front element
        const item_type& front() const
        {
            __TBB_ASSERT(my_item_valid(my_head), "attempt to fetch head non-item");
            return get_my_item(my_head);
        }

        // returns  the back element
        const item_type& back() const
        {
            __TBB_ASSERT(my_item_valid(my_tail - 1), "attempt to fetch head non-item");
            return get_my_item(my_tail - 1);
        }

        // following methods are for reservation of the front of a bufffer.
        void reserve_item(size_type i) { __TBB_ASSERT(my_item_valid(i) && !my_item_reserved(i), "item cannot be reserved"); item(i).second = reserved_item; }
        void release_item(size_type i) { __TBB_ASSERT(my_item_reserved(i), "item is not reserved"); item(i).second = has_item; }

        void destroy_front() { destroy_item(my_head); ++my_head; }
        void destroy_back() { destroy_item(my_tail-1); --my_tail; }

        // we have to be able to test against a new tail value without changing my_tail
        // grow_array doesn't work if we change my_tail when the old array is too small
        size_type size(size_t new_tail = 0) { return (new_tail ? new_tail : my_tail) - my_head; }
        size_type capacity() { return my_array_size; }
        // sequencer_node does not use this method, so we don't
        // need a version that passes in the new_tail value.
        bool buffer_full() { return size() >= capacity(); }

        //! Grows the internal array.
        void grow_my_array( size_t minimum_size ) {
            // test that we haven't made the structure inconsistent.
            __TBB_ASSERT(capacity() >= my_tail - my_head, "total items exceed capacity");
            size_type new_size = my_array_size ? 2*my_array_size : initial_buffer_size;
            while( new_size<minimum_size )
                new_size*=2;

            buffer_item_type* new_array = allocator_type().allocate(new_size);

            // initialize validity to "no"
            for( size_type i=0; i<new_size; ++i ) { new_array[i].second = no_item; }

            for( size_type i=my_head; i<my_tail; ++i) {
                if(my_item_valid(i)) {  // sequencer_node may have empty slots
                    // placement-new copy-construct; could be std::move
                    char *new_space = (char *)&(new_array[i&(new_size-1)].first);
                    (void)new(new_space) item_type(get_my_item(i));
                    new_array[i&(new_size-1)].second = item(i).second;
                }
            }

            clean_up_buffer(/*reset_pointers*/false);

            my_array = new_array;
            my_array_size = new_size;
        }

        bool push_back(item_type &v) {
            if(buffer_full()) {
                grow_my_array(size() + 1);
            }
            set_my_item(my_tail, v);
            ++my_tail;
            return true;
        }

        bool pop_back(item_type &v) {
            if (!my_item_valid(my_tail-1)) {
                return false;
            }
            v = this->back();
            destroy_back();
            return true;
        }

        bool pop_front(item_type &v) {
            if(!my_item_valid(my_head)) {
                return false;
            }
            v = this->front();
            destroy_front();
            return true;
        }

        // This is used both for reset and for grow_my_array.  In the case of grow_my_array
        // we want to retain the values of the head and tail.
        void clean_up_buffer(bool reset_pointers) {
            if (my_array) {
                for( size_type i=my_head; i<my_tail; ++i ) {
                    if(my_item_valid(i))
                        destroy_item(i);
                }
                allocator_type().deallocate(my_array,my_array_size);
            }
            my_array = NULL;
            if(reset_pointers) {
                my_head = my_tail = my_array_size = 0;
            }
        }

    public:
        //! Constructor
        item_buffer( ) : my_array(NULL), my_array_size(0),
            my_head(0), my_tail(0) {
            grow_my_array(initial_buffer_size);
        }

        ~item_buffer() {
            clean_up_buffer(/*reset_pointers*/true);
        }

        void reset() { clean_up_buffer(/*reset_pointers*/true); grow_my_array(initial_buffer_size); }

    };

    //! item_buffer with reservable front-end.  NOTE: if reserving, do not
    //* complete operation with pop_front(); use consume_front().
    //* No synchronization built-in.
    template<typename T, typename A=cache_aligned_allocator<T> >
    class reservable_item_buffer : public item_buffer<T, A> {
    protected:
        using item_buffer<T, A>::my_item_valid;
        using item_buffer<T, A>::my_head;

    public:
        reservable_item_buffer() : item_buffer<T, A>(), my_reserved(false) {}
        void reset() {my_reserved = false; item_buffer<T,A>::reset(); }
    protected:

        bool reserve_front(T &v) {
            if(my_reserved || !my_item_valid(this->my_head)) return false;
            my_reserved = true;
            // reserving the head
            v = this->front();
            this->reserve_item(this->my_head);
            return true;
        }

        void consume_front() {
            __TBB_ASSERT(my_reserved, "Attempt to consume a non-reserved item");
            this->destroy_front();
            my_reserved = false;
        }

        void release_front() {
            __TBB_ASSERT(my_reserved, "Attempt to release a non-reserved item");
            this->release_item(this->my_head);
            my_reserved = false;
        }

        bool my_reserved;
    };

}  // namespace internal

#endif // __TBB__flow_graph_item_buffer_impl_H
