/**
	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 <utility> //forward
#include <type_traits> //decay, is_nothrow_assignable
#include <algorithm> //lexicographically_compare_three_way

#include "../../utility.hpp" //strlen, strncmp

namespace rexy{

	template<class Left, class Right>
	class string_cat_expr;
	template<class Char, REXY_ALLOCATOR_CONCEPT Alloc>
	class basic_string;
	template<class Char>
	class basic_string_view;

	template<class T>
	struct is_basic_string{
		template<class Char, class Alloc>
		static std::true_type check(const basic_string<Char,Alloc>*);
		static std::false_type check(...);

		static constexpr bool value = decltype(check(std::declval<std::remove_cvref_t<T>*>()))::value;
	};

	template<class T>
	struct is_basic_string_view{
		template<class Char>
		static std::true_type check(const basic_string_view<Char>*);
		static std::false_type check(...);

		static constexpr bool value = decltype(check(std::declval<std::remove_cvref_t<T>*>()))::value;
	};

	template<class T>
	struct is_basic_string_expr{
		template<class Left, class Right>
		static std::true_type check(const string_cat_expr<Left,Right>*);
		static std::false_type check(...);

		static constexpr bool value = decltype(check(std::declval<std::remove_cvref_t<T>*>()))::value;
	};

	template<class T>
	concept BasicString = requires(const T& a){
		requires(is_basic_string<T>::value || is_basic_string_view<T>::value);
		{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 = is_basic_string_expr<T>::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 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;

	//Compare
	template<BasicString Str1, BasicString Str2>
	constexpr bool operator==(const Str1& left, const Str2& right){
		if(left.length() != right.length()){
			return false;
		}
		return !rexy::strncmp(left.c_str(), right.c_str(), left.length()+1);
	}
	template<BasicString Str1>
	constexpr bool operator==(const Str1& left, typename std::decay_t<Str1>::const_pointer right)noexcept{
		if(right == nullptr){
			return false;
		}
		const rexy::basic_string_view rstr(right);
		if(rstr.length() != left.length()){
			return false;
		}
		return !rexy::strncmp(left.c_str(), rstr.c_str(), left.length());
	}
	template<BasicString Str1>
	constexpr bool operator==(typename std::decay_t<Str1>::const_pointer left, const Str1& right)noexcept{
		if(left == nullptr){
			return false;
		}
		const rexy::basic_string_view lstr(left);
		if(lstr.length() != right.length()){
			return false;
		}
		return !rexy::strncmp(lstr.c_str(), right.c_str(), right.length());
	}
	template<BasicString Str1, BasicString Str2>
	constexpr bool operator!=(const Str1& left, const Str2& right)noexcept{
		return !(left == right);
	}
	template<BasicString Str1>
	constexpr bool operator!=(const Str1& left, typename std::decay_t<Str1>::const_pointer right)noexcept{
		return !(left == right);
	}
	template<BasicString Str1>
	constexpr bool operator!=(typename std::decay_t<Str1>::const_pointer left, const Str1& right)noexcept{
		return !(left == right);
	}

	template<BasicString Str1, BasicString Str2>
	constexpr auto operator<=>(const Str1& left, const Str2& right)noexcept{
		return std::lexicographical_compare_three_way(left.begin(), left.end(), right.begin(), right.end());
	}

	//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);
	}

	template<BasicString T, class Char>
	constexpr std::size_t find_first_of(T&& t, const Char* c, std::size_t start, std::size_t size){
		if(start > t.length()){
			return rexy::npos;
		}
		for(auto it = t.cbegin() + start;it != t.cend();++it){
			for(std::size_t i = 0;i < size;++i){
				if(*it == c[i]){
					return it - t.cbegin();
				}
			}
		}
		return rexy::npos;
	}

	template<BasicString T, class Char>
	constexpr std::size_t find_last_of(T&& t, const Char* c, std::size_t start, std::size_t size){
		if(start > t.length()){
			return rexy::npos;
		}

		const auto b = t.cend() - 1;
		const auto e = t.cbegin() - 1 - start;

		for(auto it = b;it != e;--it){
			for(std::size_t i = 0;i < size;++i){
				if(*it == c[i]){
					return it - t.cbegin();
				}
			}
		}
		return rexy::npos;
	}

}

#endif