#pragma once

#include <mutex>
#include <shared_mutex>
#include <vector>
#include <unordered_map>
#include <unordered_set>

#include "opengl/resource_management/reference_counter.hpp"
namespace zgl
{


template<typename StoreID, typename MetaData>
class resource_manager : public reference_counter
{
public:
	using gl_id_type = GLuint;
	using size_type = std::uint64_t;
	using resource_entry_type = std::pair<gl_id_type, MetaData>;

	friend class resource_handle;

	bool has_resource(StoreID store_id);

	std::optional<std::pair<resource_handle, MetaData>> get_resource(StoreID store_id);

	void collect_garbage();

	void add_resource(StoreID store_id, gl_id_type gl_id, MetaData meta);

	[[nodiscard]] size_type count_garbage();

	void extract_garbage(std::vector<gl_id_type>& dst);

	void add_reference(gl_id_type id) override;

	void remove_reference(gl_id_type id) override;

private:
	static constexpr size_type unused_resource_flag = size_type{ 1 } << (sizeof(size_type) * 8 - 1);

	size_type max_unused_collection_cycle_count;

	std::shared_mutex m_lock;
	std::unordered_map<StoreID, resource_entry_type> m_resource_lookup;
	std::unordered_map<gl_id_type, size_type> m_reference_counters;
	std::unordered_set<gl_id_type> m_unused_handles;
};

}

#define INCLUDE_RESOURCE_MANAGER_IMPLEMENTATION
#include "opengl/resource_management/resource_manager.ipp"
#undef INCLUDE_RESOURCE_MANAGER_IMPLEMENTATION