/**
	This file is a part of rexy's general purpose library
	Copyright (C) 2020 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_UTILITY_HPP
#define REXY_UTILITY_HPP

#include <utility> //forward, move
#include <cstdlib> //size_t
#include <type_traits>
#include <cstring> //strlen, strcmp, memcpy
#include <cwchar> //wcslen
#include <string> //char_traits

#include "rexy.hpp"

namespace rexy{

	namespace{
		template<class T>
		constexpr void swap(T& l, T& r)
			noexcept(std::is_nothrow_move_assignable<T>::value &&
			         std::is_nothrow_move_constructible<T>::value)
		{
			T tmp = std::move(l);
			l = std::move(r);
			r = std::move(tmp);
		}
		template<class Iter1, class Iter2>
		constexpr Iter2 swap_ranges(Iter1 start1, Iter1 end1, Iter2 start2)
			noexcept(noexcept(swap(*start1, *start2)))
		{
			while(start1 != end1){
				swap(start1++, start2++);
			}
			return start2;
		}
		template<class T, size_t N>
		constexpr void swap(T (&l)[N], T (&r)[N])
			noexcept(noexcept(swap(*l, *r)))
		{
			swap_ranges(l, l+N, r);
		}

		template<class T, class U = T>
		constexpr T exchange(T& l, U&& r)
			noexcept(std::is_nothrow_assignable<T,U&&>::value &&
			         std::is_nothrow_move_assignable<T>::value)
		{
			T old = std::move(l);
			l = std::forward<U>(r);
			return old;
		}

		template<class T>
		constexpr const T& min(const T& l, const T& r)noexcept{
			return l < r ? l : r;
		}
		template<class T, class Compare>
		constexpr const T& min(const T& l, const T& r, Compare cmp)
			noexcept(std::is_nothrow_invocable<Compare,const T&,const T&>::value)
		{
			return cmp(l, r) ? l : r;
		}
		template<class T>
		constexpr const T& max(const T& l, const T& r)noexcept{
			return l > r ? l : r;
		}
		template<class T, class Compare>
		constexpr const T& max(const T& l, const T& r, Compare cmp)
			noexcept(std::is_nothrow_invocable<Compare,const T&,const T&>::value)
		{
			return cmp(l, r) ? l : r;
		}

#ifdef __cpp_lib_is_constant_evaluated
		template<class T>
		constexpr size_t strlen(const T* c)noexcept{
			return std::char_traits<T>::length(c);
		}
		template<class T>
		constexpr int strcmp(const T* l, const T* r)noexcept{
			if(!std::is_constant_evaluated()){
				if(std::is_same_v<std::remove_cvref_t<T>,char>){
					return std::strcmp(l, r);
				}else if(std::is_same_v<std::remove_cvref_t<T>,wchar_t>){
					return std::wcscmp(l, r);
				}
			}
			for(;*l == *r && *l;++l, ++r);
			return *l - *r;
		}
		template<class T, class Compare>
		constexpr int strcmp(const T* l, const T* r, Compare cmp)noexcept{
			for(;cmp(*l, *r) && *l;++l, ++r);
			return *l - *r;
		}
		constexpr void memcpy(void* l, const void* r, size_t n){
			if(!std::is_constant_evaluated()){
				std::memcpy(l, r, n);
			}else{
				char* ld = static_cast<char*>(l);
				const char* rd = static_cast<const char*>(r);
				for(size_t i = 0;i < n;++i){
					ld[i] = rd[i];
				}
			}
		}
	}
#else //__cpp_lib_is_constant_evaluated
		template<class T>
		constexpr size_t strlen(const T* c)noexcept{
			size_t i = 0;
			for(;c[i];++i);
			return i;
		}
		template<class T>
		constexpr int strcmp(const T* l, const T* r)noexcept{
			for(;*l == *r && *l;++l, ++r);
			return *l - *r;
		}
		template<class T, class Compare>
		constexpr int strcmp(const T* l, const T* r, Compare cmp)noexcept{
			for(;cmp(*l, *r) && *l;++l, ++r);
			return *l - *r;
		}
		constexpr void memcpy(void* l, const void* r, size_t n){
			char* ld = static_cast<char*>(l);
			const char* rd = static_cast<const char*>(r);
			for(size_t i = 0;i < n;++i){
				ld[i] = rd[i];
			}
		}
	}
#endif //__cpp_lib_is_constant_evaluated

}

#endif