/**
	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_COMPAT_CPP20_STRING_BASE_HPP
#define REXY_COMPAT_CPP20_STRING_BASE_HPP

#include "../../string_base.hpp"

#include <concepts> //convertible_to
#include <utility> //forward, as_const
#include <type_traits> //decay, is_nothrow_assignable

namespace rexy{

	template<class T>
	concept BasicString = requires(const T& a){
		{std::as_const(a).length()} -> std::convertible_to<typename std::decay_t<T>::size_type>;
		{std::as_const(a).c_str()} -> std::convertible_to<typename std::decay_t<T>::const_pointer>;
		{std::as_const(a)[0]} -> std::convertible_to<typename std::decay_t<T>::const_reference>;
		{std::as_const(a).begin()} -> std::convertible_to<typename std::decay_t<T>::const_iterator>;
		{std::as_const(a).end()} -> std::convertible_to<typename std::decay_t<T>::const_iterator>;
	};
	template<class T>
	concept StringExpr = rexy::is_template_type<T,string_cat_expr>::value;
	template<class T>
	concept String = BasicString<T> || StringExpr<T>;

	template<class T>
	struct is_string{
		static constexpr bool value = BasicString<T>;
	};
	template<class T>
	static constexpr bool is_string_v = is_string<T>::value;
	template<class... Ts>
	struct are_strings{
		static constexpr bool value = (BasicString<Ts> && ...);
	};
	template<class... Ts>
	static constexpr bool are_strings_v = are_strings<Ts...>::value;
	template<class T>
	struct is_string_expr{
		static constexpr bool value = StringExpr<T>;
	};
	template<class T>
	static constexpr bool is_string_expr_v = is_string_expr<T>::value;
	template<class... Ts>
	struct are_string_expr{
		static constexpr bool value = (StringExpr<Ts> && ...);
	};
	template<class... Ts>
	static constexpr bool are_string_expr_v = are_string_expr<Ts...>::value;

	//Compare
	template<BasicString Str1, BasicString Str2>
	constexpr bool operator==(Str1&& left, Str2&& right){
		if(left.length() != right.length()){
			return false;
		}
		return !detail::string_compare(std::forward<Str1>(left), std::forward<Str2>(right), left.length());
	}
	template<BasicString Str1>
	constexpr bool operator==(Str1&& left, typename std::decay_t<Str1>::const_pointer right){
		if(right == nullptr){
			return false;
		}
		const auto rlen = detail::string_len(right);
		if(rlen != left.length()){
			return false;
		}
		const auto minlen = min(left.length(), rlen);
		return !detail::string_compare(left.c_str(), right, minlen+1);
	}
	template<BasicString Str1>
	constexpr bool operator==(typename std::decay_t<Str1>::const_pointer left, Str1&& right){
		if(left == nullptr){
			return false;
		}
		const auto llen = detail::string_len(left);
		if(llen != right.length()){
			return false;
		}
		const auto minlen = min(right.length(), llen);
		return !detail::string_compare(right.c_str(), left, minlen+1);
	}
	template<BasicString Str1, BasicString Str2>
	constexpr bool operator!=(Str1&& left, Str2&& right){
		return !(std::forward<Str1>(left) == std::forward<Str2>(right));
	}
	template<BasicString Str1>
	constexpr bool operator!=(Str1&& left, typename std::decay_t<Str1>::const_pointer right){
		return !(std::forward<Str1>(left) == right);
	}
	template<BasicString Str1>
	constexpr bool operator!=(typename std::decay_t<Str1>::const_pointer left, Str1&& right){
		return !(left == std::forward<Str1>(right));
	}

	//String + string concat
	template<String Left, String Right>
	constexpr auto operator+(Left&& l, Right&& r)
		//uses deduction guide whereas std::is_nothrow_constructible couldn't
		noexcept(noexcept(::new (nullptr) string_cat_expr(std::forward<Left>(l), std::forward<Right>(r))))
	{
		return string_cat_expr(std::forward<Left>(l), std::forward<Right>(r));
	}
	template<String Right>
	constexpr auto operator+(typename std::decay_t<Right>::const_pointer left, Right&& right)
		noexcept(noexcept(::new (nullptr) string_cat_expr(rexy::basic_string_view(left), std::forward<Right>(right))))
	{
		return string_cat_expr(rexy::basic_string_view(left), std::forward<Right>(right));
	}
	template<String Left>
	constexpr auto operator+(Left&& left, typename std::decay_t<Left>::const_pointer right)
		noexcept(noexcept(::new (nullptr) string_cat_expr(std::forward<Left>(left), rexy::basic_string_view(right))))
	{
		return rexy::string_cat_expr(std::forward<Left>(left), rexy::basic_string_view(right));
	}

	//String concat assign
	template<BasicString Left, String Right>
	constexpr decltype(auto) operator+=(Left& l, Right&& r)
		noexcept(noexcept(l + std::forward<Right>(r)) && std::is_nothrow_assignable<Left, decltype(l + std::forward<Right>(r))>::value)
	{
		return l = (l + std::forward<Right>(r));
	}
	template<BasicString Left>
	constexpr decltype(auto) operator+=(Left& l, typename std::decay_t<Left>::const_pointer r)
		noexcept(noexcept(l + r) && std::is_nothrow_assignable<Left, decltype(l + r)>::value)
	{
		return l = (l + r);
	}

}

#endif