#pragma once

/* <editor-fold desc="MIT License">

Copyright(c) 2024 Robert Osfield

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

</editor-fold> */

#include <vsg/threading/ActivityStatus.h>
#include <vsg/utils/SharedObjects.h>

#include <condition_variable>
#include <list>

namespace vsg
{

    /// Thread safe queue deleting nodes/subgraphs as batches, typically done from a background thread.
    class VSG_DECLSPEC DeleteQueue : public Inherit<Object, DeleteQueue>
    {
    public:
        explicit DeleteQueue(ref_ptr<ActivityStatus> status);

        struct ObjectToDelete
        {
            uint64_t frameCount = 0;
            ref_ptr<Object> object;
        };

        using ObjectsToDelete = std::list<ObjectToDelete>;

        std::atomic_uint64_t frameCount = 0;
        uint64_t retainForFrameCount = 3;
        std::atomic_uint64_t deletedCount = 0;

        ActivityStatus* getStatus() { return _status; }
        const ActivityStatus* getStatus() const { return _status; }

        void advance(ref_ptr<FrameStamp> frameStamp);

        void add(ref_ptr<Object> object)
        {
            std::scoped_lock lock(_mutex);
            _objectsToDelete.push_back(ObjectToDelete{frameCount + retainForFrameCount, object});
            _cv.notify_one();
        }

        template<typename T>
        void add(T& objects)
        {
            std::scoped_lock lock(_mutex);

            // register the Objects to delete
            for (auto& object : objects)
            {
                _objectsToDelete.emplace_back(ObjectToDelete{frameCount + retainForFrameCount, object});
            }

            _cv.notify_one();
        }

        void prune(ref_ptr<SharedObjects> sharedObjects)
        {
            std::scoped_lock lock(_mutex);

            // register the SharedObjects to call prune on
            if (std::find(_sharedObjectsToPrune.begin(), _sharedObjectsToPrune.end(), sharedObjects) == _sharedObjectsToPrune.end())
            {
                _sharedObjectsToPrune.push_back(sharedObjects);
            }

            _cv.notify_one();
        }

        template<typename T>
        void prune(T& sharedObjectsList)
        {
            std::scoped_lock lock(_mutex);

            // register the Objects to delete
            for (auto& sharedObjects : sharedObjectsList)
            {
                if (std::find(_sharedObjectsToPrune.begin(), _sharedObjectsToPrune.end(), sharedObjects) == _sharedObjectsToPrune.end())
                    _sharedObjectsToPrune.push_back(sharedObjects);
            }

            _cv.notify_one();
        }

        template<typename T, typename R>
        void add_prune(T& objects, R& sharedObjectsList)
        {
            std::scoped_lock lock(_mutex);

            // register the Objects to delete
            for (auto& object : objects)
            {
                _objectsToDelete.emplace_back(ObjectToDelete{frameCount + retainForFrameCount, object});
            }

            // register the SharedObjects to call prune on
            for (auto& sharedObjects : sharedObjectsList)
            {
                if (std::find(_sharedObjectsToPrune.begin(), _sharedObjectsToPrune.end(), sharedObjects) == _sharedObjectsToPrune.end())
                    _sharedObjectsToPrune.push_back(sharedObjects);
            }
            _cv.notify_one();
        }

        /// wait till there are items to delete then delete objects scheduled for deletion more than retainForFrameCount,
        /// return number of objects assigned directly to DeleteQeue that have been deleted (doesn't count children deleted.)
        size_t wait_then_clear();

        /// immediately delete objects scheduled for deletion for more than retainForFrameCount,
        /// return number of objects assigned directly to DeleteQeue that have been deleted (doesn't count children deleted.)
        size_t clear();

    protected:
        ~DeleteQueue() override;

        std::mutex _mutex;
        std::condition_variable _cv;
        ObjectsToDelete _objectsToDelete;
        std::list<ref_ptr<SharedObjects>> _sharedObjectsToPrune;

        ref_ptr<ActivityStatus> _status;
    };
    VSG_type_name(vsg::DeleteQueue);

} // namespace vsg
