gplib/include/gp/vfs/vfs.hpp

#pragma once

#include "gp_config.hpp"

#include "gp/allocator/aggregator.hpp"
#include "gp/buffer.hpp"
#include "gp/optional.hpp"
#include "gp/variant.hpp"
#include "gp/vfs/fs_types.hpp"

#include <stddef.h>

namespace gp {
	class vfs {
	private:
		struct virtual_fs
		{
			virtual ~virtual_fs() = default;
			virtual fs::open_return open(buffer<char>, fs::file_flags, fs::file_permissions) = 0;
			virtual fs::read_return read(gp_config::file_descriptor_t, buffer<char>) = 0;
			virtual fs::write_return write(gp_config::file_descriptor_t, buffer<char>, size_t) = 0;
			virtual fs::close_return close(gp_config::file_descriptor_t) = 0;
		};

		template<typename concrete>
		class abstract_fs final : public virtual_fs{
			concrete internal_representation;
		public:
			abstract_fs(abstract_fs& v) = delete;
			abstract_fs(abstract_fs&& v)
			: internal_representation{v.internal_representation}
			{}

			abstract_fs(concrete& v) = delete;
			abstract_fs(concrete&& v)
			: internal_representation{v}
			{}
			
			virtual ~abstract_fs() override = default;

			virtual fs::open_return open(buffer<char> path, fs::file_flags flags, fs::file_permissions perms) override {
				return internal_representation.open(path, flags, perms);
			}


			virtual fs::read_return read(gp_config::file_descriptor_t fd, buffer<char> buff) override {
				return internal_representation.read(fd, buff);
			}

			virtual fs::write_return write(gp_config::file_descriptor_t fd, buffer<char> buff, size_t offset) override {
				return internal_representation.write(fd, buff, offset);
			}

			virtual fs::close_return close(gp_config::file_descriptor_t fd) override {
				return internal_representation.close(fd);
			}
		};

		reference_wrapper<aggregator> allocator;
		virtual_fs* file_system;

	public:
		template<typename T>
		vfs(T&& v, reference_wrapper<aggregator> _ref)
		: allocator{_ref}
		, file_system{new(allocator.get().allocate(sizeof(T))) T(gp::move(v))}
		{}

		fs::open_return open(buffer<char> path, fs::file_flags flags, fs::file_permissions perms) {
			return file_system->open(path, flags, perms);
		}


		fs::read_return read(gp_config::file_descriptor_t fd, buffer<char> buff) {
			return file_system->read(fd, buff);
		}

		fs::write_return write(gp_config::file_descriptor_t fd, buffer<char> buff, size_t offset) {
			return file_system->write(fd, buff, offset);
		}

		fs::close_return close(gp_config::file_descriptor_t fd) {
			return file_system->close(fd);
		}

		~vfs() {
			file_system->~virtual_fs();
			allocator.get().deallocate(file_system);
		}
	};
}