/**
	This file is a part of rexy's general purpose library
	Copyright (C) 2022 rexy712

	This program is free software: you can redistribute it and/or modify
	it under the terms of the GNU General Public License as published by
	the Free Software Foundation, either version 3 of the License, or
	(at your option) any later version.

	This program is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
	GNU General Public License for more details.

	You should have received a copy of the GNU General Public License
	along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#ifndef REXY_DETAIL_FORMAT_FORMAT_ARGS_HPP
#define REXY_DETAIL_FORMAT_FORMAT_ARGS_HPP

#include <cstddef> //size_t
#include <variant> //monostate

#include "storage.hpp" //storage_type
#include "basic_types.hpp" //arg_info
#include "arg_store.hpp"
#include "traits.hpp"

#include "../../string_view.hpp"

namespace rexy::fmt{

	//Type erasure of single argument.
	//Context is an instantiation of 'basic_format_context'
	template<class Context>
	class basic_format_arg
	{
	public:
		using char_type = typename Context::char_type;

	public:
		//Handles call to formatter for a user defined type
		//type erase the user defined values
		class handle
		{
		public:
			using format_ptr_t = void(handle::*)(basic_format_parse_context<char_type>&, Context&)const;
		public:
			const void* m_data;
			format_ptr_t m_format_impl;
		public:
			template<class T>
			explicit handle(T&& t);
			template<class T>
			void format_impl(basic_format_parse_context<char_type>& parse_ctx, Context& format_ctx)const;
			void format(basic_format_parse_context<char_type>& parse_ctx, Context& format_ctx)const;
		};

		union{
			std::monostate none_v = {};
			bool bool_v;
			char_type char_v;
			int int_v;
			unsigned int uint_v;
			long long long_long_v;
			unsigned long long ulong_long_v;
			float float_v;
			double double_v;
			long double long_double_v;
			const char_type* char_ptr_v;
			basic_string_view<char_type> string_v;
			const void* ptr_v;
			handle custom_v;
		};
		detail::storage_type active_member = detail::storage_type::none_t;

		//initialize std::variant equivalent to std::monostate
		basic_format_arg(void)noexcept{}

		explicit basic_format_arg(bool b)noexcept;
		explicit basic_format_arg(char_type b)noexcept;
		explicit basic_format_arg(int b)noexcept;
		explicit basic_format_arg(unsigned int b)noexcept;
		explicit basic_format_arg(long long b)noexcept;
		explicit basic_format_arg(unsigned long long b)noexcept;
		explicit basic_format_arg(float b)noexcept;
		explicit basic_format_arg(double b)noexcept;
		explicit basic_format_arg(long double b)noexcept;
		explicit basic_format_arg(const char_type* b)noexcept;
		explicit basic_format_arg(basic_string_view<char_type> b)noexcept;
		explicit basic_format_arg(const void* b)noexcept;
		explicit basic_format_arg(const handle b)noexcept;

		detail::storage_type type(void)const;

		explicit operator bool(void)const noexcept;
	};

	//Holds list of arguments, erasing concrete types.
	//Context is an instantiation of 'basic_format_context'
	template<class Context>
	class basic_format_args
	{
	public:
		using char_type = detail::extract_char_type_from_context_t<Context>;
	private:
		//TODO less pointers
		const detail::arg_info* m_info = nullptr;
		const unsigned char* m_data = nullptr;
		const std::size_t m_num_args = 0;

	public:
		basic_format_args(void)noexcept = default;

		constexpr basic_format_args(const detail::basic_format_arg_store<Context>& store)noexcept;
		template<class... Args>
		basic_format_args(const detail::basic_format_arg_store<Context,Args...>& store)noexcept;

		basic_format_arg<Context> get(std::size_t i)const noexcept;
		basic_format_arg<Context> get(const char_type* first, const char_type* last)const;
		std::size_t get_index(const char_type* first, const char_type* last)const;
	};

	//Visitor for basic_format_arg
	template<class Fun, class Context>
	decltype(auto) visit_format_arg(Fun&& fun, const basic_format_arg<Context>& arg);
}

#endif