// sol3

// The MIT License (MIT)

// Copyright (c) 2013-2020 Rapptz, ThePhD and contributors

// 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.

#ifndef SOL_STATE_VIEW_HPP
#define SOL_STATE_VIEW_HPP

#include <sol/error.hpp>
#include <sol/table.hpp>
#include <sol/environment.hpp>
#include <sol/load_result.hpp>
#include <sol/state_handling.hpp>

#include <memory>
#include <cstddef>

namespace sol {

	class state_view {
	private:
		lua_State* L;
		table reg;
		global_table global;

		optional<object> is_loaded_package(const std::string& key) {
			auto loaded = reg.traverse_get<optional<object>>("_LOADED", key);
			bool is53mod = loaded && !(loaded->is<bool>() && !loaded->as<bool>());
			if (is53mod)
				return loaded;
#if SOL_LUA_VERSION <= 501
			auto loaded51 = global.traverse_get<optional<object>>("package", "loaded", key);
			bool is51mod = loaded51 && !(loaded51->is<bool>() && !loaded51->as<bool>());
			if (is51mod)
				return loaded51;
#endif
			return nullopt;
		}

		template <typename T>
		void ensure_package(const std::string& key, T&& sr) {
#if SOL_LUA_VERSION <= 501
			auto pkg = global["package"];
			if (!pkg.valid()) {
				pkg = create_table_with("loaded", create_table_with(key, sr));
			}
			else {
				auto ld = pkg["loaded"];
				if (!ld.valid()) {
					ld = create_table_with(key, sr);
				}
				else {
					ld[key] = sr;
				}
			}
#endif
			auto loaded = reg["_LOADED"];
			if (!loaded.valid()) {
				loaded = create_table_with(key, sr);
			}
			else {
				loaded[key] = sr;
			}
		}

		template <typename Fx>
		object require_core(const std::string& key, Fx&& action, bool create_global = true) {
			optional<object> loaded = is_loaded_package(key);
			if (loaded && loaded->valid())
				return std::move(*loaded);
			action();
			stack_reference sr(L, -1);
			if (create_global)
				set(key, sr);
			ensure_package(key, sr);
			return stack::pop<object>(L);
		}

	public:
		using iterator = typename global_table::iterator;
		using const_iterator = typename global_table::const_iterator;

		state_view(lua_State* Ls) : L(Ls), reg(Ls, LUA_REGISTRYINDEX), global(Ls, detail::global_) {
		}

		state_view(this_state Ls) : state_view(Ls.L) {
		}

		lua_State* lua_state() const {
			return L;
		}

		template <typename... Args>
		void open_libraries(Args&&... args) {
			static_assert(meta::all_same<lib, meta::unqualified_t<Args>...>::value, "all types must be libraries");
			if constexpr (sizeof...(args) == 0) {
				luaL_openlibs(L);
				return;
			}
			else {
				lib libraries[1 + sizeof...(args)] = { lib::count, std::forward<Args>(args)... };

				for (auto&& library : libraries) {
					switch (library) {
#if SOL_LUA_VERSION <= 501 && defined(SOL_LUAJIT)
					case lib::coroutine:
#endif // luajit opens coroutine base stuff
					case lib::base:
						luaL_requiref(L, "base", luaopen_base, 1);
						lua_pop(L, 1);
						break;
					case lib::package:
						luaL_requiref(L, "package", luaopen_package, 1);
						lua_pop(L, 1);
						break;
#if !defined(SOL_LUAJIT)
					case lib::coroutine:
#if SOL_LUA_VERSION > 501
						luaL_requiref(L, "coroutine", luaopen_coroutine, 1);
						lua_pop(L, 1);
#endif // Lua 5.2+ only
						break;
#endif // Not LuaJIT - comes builtin
					case lib::string:
						luaL_requiref(L, "string", luaopen_string, 1);
						lua_pop(L, 1);
						break;
					case lib::table:
						luaL_requiref(L, "table", luaopen_table, 1);
						lua_pop(L, 1);
						break;
					case lib::math:
						luaL_requiref(L, "math", luaopen_math, 1);
						lua_pop(L, 1);
						break;
					case lib::bit32:
#ifdef SOL_LUAJIT
						luaL_requiref(L, "bit32", luaopen_bit, 1);
						lua_pop(L, 1);
#elif (SOL_LUA_VERSION == 502) || defined(LUA_COMPAT_BITLIB) || defined(LUA_COMPAT_5_2)
						luaL_requiref(L, "bit32", luaopen_bit32, 1);
						lua_pop(L, 1);
#else
#endif // Lua 5.2 only (deprecated in 5.3 (503)) (Can be turned on with Compat flags)
						break;
					case lib::io:
						luaL_requiref(L, "io", luaopen_io, 1);
						lua_pop(L, 1);
						break;
					case lib::os:
						luaL_requiref(L, "os", luaopen_os, 1);
						lua_pop(L, 1);
						break;
					case lib::debug:
						luaL_requiref(L, "debug", luaopen_debug, 1);
						lua_pop(L, 1);
						break;
					case lib::utf8:
#if SOL_LUA_VERSION > 502 && !defined(SOL_LUAJIT)
						luaL_requiref(L, "utf8", luaopen_utf8, 1);
						lua_pop(L, 1);
#endif // Lua 5.3+ only
						break;
					case lib::ffi:
#ifdef SOL_LUAJIT
						luaL_requiref(L, "ffi", luaopen_ffi, 1);
						lua_pop(L, 1);
#endif // LuaJIT only
						break;
					case lib::jit:
#ifdef SOL_LUAJIT
						luaL_requiref(L, "jit", luaopen_jit, 0);
						lua_pop(L, 1);
#endif // LuaJIT Only
						break;
					case lib::count:
					default:
						break;
					}
				}
			}
		}

		object require(const std::string& key, lua_CFunction open_function, bool create_global = true) {
			luaL_requiref(L, key.c_str(), open_function, create_global ? 1 : 0);
			return stack::pop<object>(L);
		}

		object require_script(const std::string& key, const string_view& code, bool create_global = true,
		     const std::string& chunkname = detail::default_chunk_name(), load_mode mode = load_mode::any) {
			auto action = [this, &code, &chunkname, &mode]() { stack::script(L, code, chunkname, mode); };
			return require_core(key, action, create_global);
		}

		object require_file(const std::string& key, const std::string& filename, bool create_global = true, load_mode mode = load_mode::any) {
			auto action = [this, &filename, &mode]() { stack::script_file(L, filename, mode); };
			return require_core(key, action, create_global);
		}

		void clear_package_loaders() {
			optional<table> maybe_package = this->global["package"];
			if (!maybe_package) {
				// package lib wasn't opened
				// open package lib
				return;
			}
			table& package = *maybe_package;
			// yay for version differences...
			// one day Lua 5.1 will die a peaceful death
			// and its old bones will find blissful rest
			auto loaders_proxy = package
#if SOL_LUA_VERSION < 502
			     ["loaders"]
#else
			     ["searchers"]
#endif
			     ;
			if (!loaders_proxy.valid()) {
				// nothing to clear
				return;
			}
			// we need to create the table for loaders
			// table does not exist, so create and move forward
			loaders_proxy = new_table(1, 0);
		}

		template <typename Fx>
		void add_package_loader(Fx&& fx, bool clear_all_package_loaders = false) {
			optional<table> maybe_package = this->global["package"];
			if (!maybe_package) {
				// package lib wasn't opened
				// open package lib
				return;
			}
			table& package = *maybe_package;
			// yay for version differences...
			// one day Lua 5.1 will die a peaceful death
			// and its old bones will find blissful rest
			auto loaders_proxy = package
#if SOL_LUA_VERSION < 502
			     ["loaders"]
#else
			     ["searchers"]
#endif
			     ;
			bool make_new_table = clear_all_package_loaders || !loaders_proxy.valid();
			if (make_new_table) {
				// we need to create the table for loaders
				// table does not exist, so create and move forward
				loaders_proxy = new_table(1, 0);
			}
			optional<table> maybe_loaders = loaders_proxy;
			if (!maybe_loaders) {
				// loaders/searches
				// thing exists in package, but it
				// ain't a table or a table-alike...!
				return;
			}
			table loaders = loaders_proxy;
			loaders.add(std::forward<Fx>(fx));
		}

		template <typename E>
		protected_function_result do_reader(lua_Reader reader, void* data, const basic_environment<E>& env,
		     const std::string& chunkname = detail::default_chunk_name(), load_mode mode = load_mode::any) {
			detail::typical_chunk_name_t basechunkname = {};
			const char* chunknametarget = detail::make_chunk_name("lua_Reader", chunkname, basechunkname);
			load_status x = static_cast<load_status>(lua_load(L, reader, data, chunknametarget, to_string(mode).c_str()));
			if (x != load_status::ok) {
				return protected_function_result(L, absolute_index(L, -1), 0, 1, static_cast<call_status>(x));
			}
			stack_aligned_protected_function pf(L, -1);
			set_environment(env, pf);
			return pf();
		}

		protected_function_result do_reader(
		     lua_Reader reader, void* data, const std::string& chunkname = detail::default_chunk_name(), load_mode mode = load_mode::any) {
			detail::typical_chunk_name_t basechunkname = {};
			const char* chunknametarget = detail::make_chunk_name("lua_Reader", chunkname, basechunkname);
			load_status x = static_cast<load_status>(lua_load(L, reader, data, chunknametarget, to_string(mode).c_str()));
			if (x != load_status::ok) {
				return protected_function_result(L, absolute_index(L, -1), 0, 1, static_cast<call_status>(x));
			}
			stack_aligned_protected_function pf(L, -1);
			return pf();
		}

		template <typename E>
		protected_function_result do_string(const string_view& code, const basic_environment<E>& env,
		     const std::string& chunkname = detail::default_chunk_name(), load_mode mode = load_mode::any) {
			detail::typical_chunk_name_t basechunkname = {};
			const char* chunknametarget = detail::make_chunk_name(code, chunkname, basechunkname);
			load_status x = static_cast<load_status>(luaL_loadbufferx(L, code.data(), code.size(), chunknametarget, to_string(mode).c_str()));
			if (x != load_status::ok) {
				return protected_function_result(L, absolute_index(L, -1), 0, 1, static_cast<call_status>(x));
			}
			stack_aligned_protected_function pf(L, -1);
			set_environment(env, pf);
			return pf();
		}

		protected_function_result do_string(
		     const string_view& code, const std::string& chunkname = detail::default_chunk_name(), load_mode mode = load_mode::any) {
			detail::typical_chunk_name_t basechunkname = {};
			const char* chunknametarget = detail::make_chunk_name(code, chunkname, basechunkname);
			load_status x = static_cast<load_status>(luaL_loadbufferx(L, code.data(), code.size(), chunknametarget, to_string(mode).c_str()));
			if (x != load_status::ok) {
				return protected_function_result(L, absolute_index(L, -1), 0, 1, static_cast<call_status>(x));
			}
			stack_aligned_protected_function pf(L, -1);
			return pf();
		}

		template <typename E>
		protected_function_result do_file(const std::string& filename, const basic_environment<E>& env, load_mode mode = load_mode::any) {
			load_status x = static_cast<load_status>(luaL_loadfilex(L, filename.c_str(), to_string(mode).c_str()));
			if (x != load_status::ok) {
				return protected_function_result(L, absolute_index(L, -1), 0, 1, static_cast<call_status>(x));
			}
			stack_aligned_protected_function pf(L, -1);
			set_environment(env, pf);
			return pf();
		}

		protected_function_result do_file(const std::string& filename, load_mode mode = load_mode::any) {
			load_status x = static_cast<load_status>(luaL_loadfilex(L, filename.c_str(), to_string(mode).c_str()));
			if (x != load_status::ok) {
				return protected_function_result(L, absolute_index(L, -1), 0, 1, static_cast<call_status>(x));
			}
			stack_aligned_protected_function pf(L, -1);
			return pf();
		}

		template <typename Fx,
		     meta::disable_any<meta::is_string_constructible<meta::unqualified_t<Fx>>,
		          meta::is_specialization_of<meta::unqualified_t<Fx>, basic_environment>> = meta::enabler>
		protected_function_result safe_script(
		     lua_Reader reader, void* data, Fx&& on_error, const std::string& chunkname = detail::default_chunk_name(), load_mode mode = load_mode::any) {
			protected_function_result pfr = do_reader(reader, data, chunkname, mode);
			if (!pfr.valid()) {
				return on_error(L, std::move(pfr));
			}
			return pfr;
		}

		protected_function_result safe_script(
		     lua_Reader reader, void* data, const std::string& chunkname = detail::default_chunk_name(), load_mode mode = load_mode::any) {
			return safe_script(reader, data, script_default_on_error, chunkname, mode);
		}

		template <typename Fx,
		     meta::disable_any<meta::is_string_constructible<meta::unqualified_t<Fx>>,
		          meta::is_specialization_of<meta::unqualified_t<Fx>, basic_environment>> = meta::enabler>
		protected_function_result safe_script(
		     const string_view& code, Fx&& on_error, const std::string& chunkname = detail::default_chunk_name(), load_mode mode = load_mode::any) {
			protected_function_result pfr = do_string(code, chunkname, mode);
			if (!pfr.valid()) {
				return on_error(L, std::move(pfr));
			}
			return pfr;
		}

		template <typename Fx, typename E>
		protected_function_result safe_script(const string_view& code, const basic_environment<E>& env, Fx&& on_error,
		     const std::string& chunkname = detail::default_chunk_name(), load_mode mode = load_mode::any) {
			protected_function_result pfr = do_string(code, env, chunkname, mode);
			if (!pfr.valid()) {
				return on_error(L, std::move(pfr));
			}
			return pfr;
		}

		template <typename E>
		protected_function_result safe_script(const string_view& code, const basic_environment<E>& env,
		     const std::string& chunkname = detail::default_chunk_name(), load_mode mode = load_mode::any) {
			return safe_script(code, env, script_default_on_error, chunkname, mode);
		}

		protected_function_result safe_script(
		     const string_view& code, const std::string& chunkname = detail::default_chunk_name(), load_mode mode = load_mode::any) {
			return safe_script(code, script_default_on_error, chunkname, mode);
		}

		template <typename Fx,
		     meta::disable_any<meta::is_string_constructible<meta::unqualified_t<Fx>>,
		          meta::is_specialization_of<meta::unqualified_t<Fx>, basic_environment>> = meta::enabler>
		protected_function_result safe_script_file(const std::string& filename, Fx&& on_error, load_mode mode = load_mode::any) {
			protected_function_result pfr = do_file(filename, mode);
			if (!pfr.valid()) {
				return on_error(L, std::move(pfr));
			}
			return pfr;
		}

		template <typename Fx, typename E>
		protected_function_result safe_script_file(
		     const std::string& filename, const basic_environment<E>& env, Fx&& on_error, load_mode mode = load_mode::any) {
			protected_function_result pfr = do_file(filename, env, mode);
			if (!pfr.valid()) {
				return on_error(L, std::move(pfr));
			}
			return pfr;
		}

		template <typename E>
		protected_function_result safe_script_file(const std::string& filename, const basic_environment<E>& env, load_mode mode = load_mode::any) {
			return safe_script_file(filename, env, script_default_on_error, mode);
		}

		protected_function_result safe_script_file(const std::string& filename, load_mode mode = load_mode::any) {
			return safe_script_file(filename, script_default_on_error, mode);
		}

		template <typename E>
		unsafe_function_result unsafe_script(lua_Reader reader, void* data, const basic_environment<E>& env,
		     const std::string& chunkname = detail::default_chunk_name(), load_mode mode = load_mode::any) {
			detail::typical_chunk_name_t basechunkname = {};
			const char* chunknametarget = detail::make_chunk_name("lua_Reader", chunkname, basechunkname);
			int index = lua_gettop(L);
			if (lua_load(L, reader, data, chunknametarget, to_string(mode).c_str())) {
				lua_error(L);
			}
			set_environment(env, stack_reference(L, raw_index(index + 1)));
			if (lua_pcall(L, 0, LUA_MULTRET, 0)) {
				lua_error(L);
			}
			int postindex = lua_gettop(L);
			int returns = postindex - index;
			return unsafe_function_result(L, (std::max)(postindex - (returns - 1), 1), returns);
		}

		unsafe_function_result unsafe_script(
		     lua_Reader reader, void* data, const std::string& chunkname = detail::default_chunk_name(), load_mode mode = load_mode::any) {
			int index = lua_gettop(L);
			stack::script(L, reader, data, chunkname, mode);
			int postindex = lua_gettop(L);
			int returns = postindex - index;
			return unsafe_function_result(L, (std::max)(postindex - (returns - 1), 1), returns);
		}

		template <typename E>
		unsafe_function_result unsafe_script(const string_view& code, const basic_environment<E>& env,
		     const std::string& chunkname = detail::default_chunk_name(), load_mode mode = load_mode::any) {
			detail::typical_chunk_name_t basechunkname = {};
			const char* chunknametarget = detail::make_chunk_name(code, chunkname, basechunkname);
			int index = lua_gettop(L);
			if (luaL_loadbufferx(L, code.data(), code.size(), chunknametarget, to_string(mode).c_str())) {
				lua_error(L);
			}
			set_environment(env, stack_reference(L, raw_index(index + 1)));
			if (lua_pcall(L, 0, LUA_MULTRET, 0)) {
				lua_error(L);
			}
			int postindex = lua_gettop(L);
			int returns = postindex - index;
			return unsafe_function_result(L, (std::max)(postindex - (returns - 1), 1), returns);
		}

		unsafe_function_result unsafe_script(
		     const string_view& code, const std::string& chunkname = detail::default_chunk_name(), load_mode mode = load_mode::any) {
			int index = lua_gettop(L);
			stack::script(L, code, chunkname, mode);
			int postindex = lua_gettop(L);
			int returns = postindex - index;
			return unsafe_function_result(L, (std::max)(postindex - (returns - 1), 1), returns);
		}

		template <typename E>
		unsafe_function_result unsafe_script_file(const std::string& filename, const basic_environment<E>& env, load_mode mode = load_mode::any) {
			int index = lua_gettop(L);
			if (luaL_loadfilex(L, filename.c_str(), to_string(mode).c_str())) {
				lua_error(L);
			}
			set_environment(env, stack_reference(L, raw_index(index + 1)));
			if (lua_pcall(L, 0, LUA_MULTRET, 0)) {
				lua_error(L);
			}
			int postindex = lua_gettop(L);
			int returns = postindex - index;
			return unsafe_function_result(L, (std::max)(postindex - (returns - 1), 1), returns);
		}

		unsafe_function_result unsafe_script_file(const std::string& filename, load_mode mode = load_mode::any) {
			int index = lua_gettop(L);
			stack::script_file(L, filename, mode);
			int postindex = lua_gettop(L);
			int returns = postindex - index;
			return unsafe_function_result(L, (std::max)(postindex - (returns - 1), 1), returns);
		}

		template <typename Fx,
		     meta::disable_any<meta::is_string_constructible<meta::unqualified_t<Fx>>,
		          meta::is_specialization_of<meta::unqualified_t<Fx>, basic_environment>> = meta::enabler>
		protected_function_result script(
		     const string_view& code, Fx&& on_error, const std::string& chunkname = detail::default_chunk_name(), load_mode mode = load_mode::any) {
			return safe_script(code, std::forward<Fx>(on_error), chunkname, mode);
		}

		template <typename Fx,
		     meta::disable_any<meta::is_string_constructible<meta::unqualified_t<Fx>>,
		          meta::is_specialization_of<meta::unqualified_t<Fx>, basic_environment>> = meta::enabler>
		protected_function_result script_file(const std::string& filename, Fx&& on_error, load_mode mode = load_mode::any) {
			return safe_script_file(filename, std::forward<Fx>(on_error), mode);
		}

		template <typename Fx, typename E>
		protected_function_result script(const string_view& code, const basic_environment<E>& env, Fx&& on_error,
		     const std::string& chunkname = detail::default_chunk_name(), load_mode mode = load_mode::any) {
			return safe_script(code, env, std::forward<Fx>(on_error), chunkname, mode);
		}

		template <typename Fx, typename E>
		protected_function_result script_file(const std::string& filename, const basic_environment<E>& env, Fx&& on_error, load_mode mode = load_mode::any) {
			return safe_script_file(filename, env, std::forward<Fx>(on_error), mode);
		}

		protected_function_result script(
		     const string_view& code, const environment& env, const std::string& chunkname = detail::default_chunk_name(), load_mode mode = load_mode::any) {
			return safe_script(code, env, script_default_on_error, chunkname, mode);
		}

		protected_function_result script_file(const std::string& filename, const environment& env, load_mode mode = load_mode::any) {
			return safe_script_file(filename, env, script_default_on_error, mode);
		}

#if SOL_IS_ON(SOL_SAFE_FUNCTION_OBJECTS_I_)
		protected_function_result script(
		     lua_Reader reader, void* data, const std::string& chunkname = detail::default_chunk_name(), load_mode mode = load_mode::any) {
			return safe_script(reader, data, chunkname, mode);
		}

		protected_function_result script(
		     const string_view& code, const std::string& chunkname = detail::default_chunk_name(), load_mode mode = load_mode::any) {
			return safe_script(code, chunkname, mode);
		}

		protected_function_result script_file(const std::string& filename, load_mode mode = load_mode::any) {
			return safe_script_file(filename, mode);
		}
#else
		unsafe_function_result script(const string_view& code, const std::string& chunkname = detail::default_chunk_name(), load_mode mode = load_mode::any) {
			return unsafe_script(code, chunkname, mode);
		}

		unsafe_function_result script_file(const std::string& filename, load_mode mode = load_mode::any) {
			return unsafe_script_file(filename, mode);
		}
#endif
		load_result load(const string_view& code, const std::string& chunkname = detail::default_chunk_name(), load_mode mode = load_mode::any) {
			detail::typical_chunk_name_t basechunkname = {};
			const char* chunknametarget = detail::make_chunk_name(code, chunkname, basechunkname);
			load_status x = static_cast<load_status>(luaL_loadbufferx(L, code.data(), code.size(), chunknametarget, to_string(mode).c_str()));
			return load_result(L, absolute_index(L, -1), 1, 1, x);
		}

		load_result load_buffer(const char* buff, size_t size, const std::string& chunkname = detail::default_chunk_name(), load_mode mode = load_mode::any) {
			return load(string_view(buff, size), chunkname, mode);
		}

		load_result load_buffer(
		     const std::byte* buff, size_t size, const std::string& chunkname = detail::default_chunk_name(), load_mode mode = load_mode::any) {
			return load(string_view(reinterpret_cast<const char*>(buff), size), chunkname, mode);
		}

		load_result load_file(const std::string& filename, load_mode mode = load_mode::any) {
			load_status x = static_cast<load_status>(luaL_loadfilex(L, filename.c_str(), to_string(mode).c_str()));
			return load_result(L, absolute_index(L, -1), 1, 1, x);
		}

		load_result load(lua_Reader reader, void* data, const std::string& chunkname = detail::default_chunk_name(), load_mode mode = load_mode::any) {
			detail::typical_chunk_name_t basechunkname = {};
			const char* chunknametarget = detail::make_chunk_name("lua_Reader", chunkname, basechunkname);
			load_status x = static_cast<load_status>(lua_load(L, reader, data, chunknametarget, to_string(mode).c_str()));
			return load_result(L, absolute_index(L, -1), 1, 1, x);
		}

		iterator begin() const {
			return global.begin();
		}

		iterator end() const {
			return global.end();
		}

		const_iterator cbegin() const {
			return global.cbegin();
		}

		const_iterator cend() const {
			return global.cend();
		}

		global_table globals() const {
			// if we return a reference
			// we'll be screwed a bit
			return global;
		}

		global_table& globals() {
			return global;
		}

		table registry() const {
			return reg;
		}

		std::size_t memory_used() const {
			return total_memory_used(lua_state());
		}

		int stack_top() const {
			return stack::top(L);
		}

		int stack_clear() {
			int s = stack_top();
			lua_pop(L, s);
			return s;
		}

		bool supports_gc_mode(gc_mode mode) const noexcept {
#if SOL_LUA_VERSION >= 504
			// supports all modes
			(void)mode;
			return true;
#endif
			return mode == gc_mode::default_value;
		}

		bool is_gc_on() const {
			return lua_gc(lua_state(), LUA_GCISRUNNING, 0) == 1;
		}

		void collect_garbage() {
			lua_gc(lua_state(), LUA_GCCOLLECT, 0);
		}

		void collect_gc() {
			collect_garbage();
		}

		bool step_gc(int step_size_kilobytes) {
			// THOUGHT: std::chrono-alikes to map "kilobyte size" here...?
			// Make it harder to give MB or KB to a B parameter...?
			// Probably overkill for now.
#if SOL_LUA_VERSION >= 504
			// The manual implies that this function is almost always successful...
			// is it?? It could depend on the GC mode...
			return lua_gc(lua_state(), LUA_GCSTEP, step_size_kilobytes) != 0;
#else
			return lua_gc(lua_state(), LUA_GCSTEP, step_size_kilobytes) == 1;
#endif
		}

		void restart_gc() {
			lua_gc(lua_state(), LUA_GCRESTART, 0);
		}

		void stop_gc() {
			lua_gc(lua_state(), LUA_GCSTOP, 0);
		}

		// Returns the old GC mode. Check support using the supports_gc_mode function.
		gc_mode change_gc_mode_incremental(int pause, int step_multiplier, int step_byte_size) {
			// "What the fuck does any of this mean??"
			// http://www.lua.org/manual/5.4/manual.html#2.5.1

			// THOUGHT: std::chrono-alikes to map "byte size" here...?
			// Make it harder to give MB or KB to a B parameter...?
			// Probably overkill for now.
#if SOL_LUA_VERSION >= 504
			int old_mode = lua_gc(lua_state(), LUA_GCINC, pause, step_multiplier, step_byte_size);
			if (old_mode == LUA_GCGEN) {
				return gc_mode::generational;
			}
			else if (old_mode == LUA_GCINC) {
				return gc_mode::incremental;
			}
#else
			lua_gc(lua_state(), LUA_GCSETPAUSE, pause);
			lua_gc(lua_state(), LUA_GCSETSTEPMUL, step_multiplier);
			(void)step_byte_size; // means nothing in older versions
#endif
			return gc_mode::default_value;
		}

		// Returns the old GC mode. Check support using the supports_gc_mode function.
		gc_mode change_gc_mode_generational(int minor_multiplier, int major_multiplier) {
#if SOL_LUA_VERSION >= 504
			// "What does this shit mean?"
			// http://www.lua.org/manual/5.4/manual.html#2.5.2
			int old_mode = lua_gc(lua_state(), LUA_GCGEN, minor_multiplier, major_multiplier);
			if (old_mode == LUA_GCGEN) {
				return gc_mode::generational;
			}
			else if (old_mode == LUA_GCINC) {
				return gc_mode::incremental;
			}
#endif
			return gc_mode::default_value;
		}

		operator lua_State*() const {
			return lua_state();
		}

		void set_panic(lua_CFunction panic) {
			lua_atpanic(lua_state(), panic);
		}

		void set_exception_handler(exception_handler_function handler) {
			set_default_exception_handler(lua_state(), handler);
		}

		template <typename... Args, typename... Keys>
		decltype(auto) get(Keys&&... keys) const {
			return global.get<Args...>(std::forward<Keys>(keys)...);
		}

		template <typename T, typename Key>
		decltype(auto) get_or(Key&& key, T&& otherwise) const {
			return global.get_or(std::forward<Key>(key), std::forward<T>(otherwise));
		}

		template <typename T, typename Key, typename D>
		decltype(auto) get_or(Key&& key, D&& otherwise) const {
			return global.get_or<T>(std::forward<Key>(key), std::forward<D>(otherwise));
		}

		template <typename... Args>
		state_view& set(Args&&... args) {
			global.set(std::forward<Args>(args)...);
			return *this;
		}

		template <typename T, typename... Keys>
		decltype(auto) traverse_get(Keys&&... keys) const {
			return global.traverse_get<T>(std::forward<Keys>(keys)...);
		}

		template <typename... Args>
		state_view& traverse_set(Args&&... args) {
			global.traverse_set(std::forward<Args>(args)...);
			return *this;
		}

		template <typename Class, typename... Args>
		usertype<Class> new_usertype(const std::string& name, Args&&... args) {
			return global.new_usertype<Class>(name, std::forward<Args>(args)...);
		}

		template <bool read_only = true, typename... Args>
		state_view& new_enum(const string_view& name, Args&&... args) {
			global.new_enum<read_only>(name, std::forward<Args>(args)...);
			return *this;
		}

		template <typename T, bool read_only = true>
		state_view& new_enum(const string_view& name, std::initializer_list<std::pair<string_view, T>> items) {
			global.new_enum<T, read_only>(name, std::move(items));
			return *this;
		}

		template <typename Fx>
		void for_each(Fx&& fx) {
			global.for_each(std::forward<Fx>(fx));
		}

		template <typename T>
		table_proxy<global_table&, detail::proxy_key_t<T>> operator[](T&& key) {
			return global[std::forward<T>(key)];
		}

		template <typename T>
		table_proxy<const global_table&, detail::proxy_key_t<T>> operator[](T&& key) const {
			return global[std::forward<T>(key)];
		}

		template <typename Sig, typename... Args, typename Key>
		state_view& set_function(Key&& key, Args&&... args) {
			global.set_function<Sig>(std::forward<Key>(key), std::forward<Args>(args)...);
			return *this;
		}

		template <typename... Args, typename Key>
		state_view& set_function(Key&& key, Args&&... args) {
			global.set_function(std::forward<Key>(key), std::forward<Args>(args)...);
			return *this;
		}

		template <typename Name>
		table create_table(Name&& name, int narr = 0, int nrec = 0) {
			return global.create(std::forward<Name>(name), narr, nrec);
		}

		template <typename Name, typename Key, typename Value, typename... Args>
		table create_table(Name&& name, int narr, int nrec, Key&& key, Value&& value, Args&&... args) {
			return global.create(std::forward<Name>(name), narr, nrec, std::forward<Key>(key), std::forward<Value>(value), std::forward<Args>(args)...);
		}

		template <typename Name, typename... Args>
		table create_named_table(Name&& name, Args&&... args) {
			table x = global.create_with(std::forward<Args>(args)...);
			global.set(std::forward<Name>(name), x);
			return x;
		}

		table create_table(int narr = 0, int nrec = 0) {
			return create_table(lua_state(), narr, nrec);
		}

		template <typename Key, typename Value, typename... Args>
		table create_table(int narr, int nrec, Key&& key, Value&& value, Args&&... args) {
			return create_table(lua_state(), narr, nrec, std::forward<Key>(key), std::forward<Value>(value), std::forward<Args>(args)...);
		}

		template <typename... Args>
		table create_table_with(Args&&... args) {
			return create_table_with(lua_state(), std::forward<Args>(args)...);
		}

		static inline table create_table(lua_State* L, int narr = 0, int nrec = 0) {
			return global_table::create(L, narr, nrec);
		}

		template <typename Key, typename Value, typename... Args>
		static inline table create_table(lua_State* L, int narr, int nrec, Key&& key, Value&& value, Args&&... args) {
			return global_table::create(L, narr, nrec, std::forward<Key>(key), std::forward<Value>(value), std::forward<Args>(args)...);
		}

		template <typename... Args>
		static inline table create_table_with(lua_State* L, Args&&... args) {
			return global_table::create_with(L, std::forward<Args>(args)...);
		}
	};
} // namespace sol

#endif // SOL_STATE_VIEW_HPP