/**
	This file is a part of r0nk, atlas_moon, and rexy's matrix client
	Copyright (C) 2019 rexy712

	This program is free software: you can redistribute it and/or modify
	it under the terms of the GNU Affero 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 Affero General Public License for more details.

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

#ifndef RAII_STRING_BASE_HPP
#define RAII_STRING_BASE_HPP

#include <cstddef> //size_t
#include <cstring> //strlen, strcpy
#include <cstdlib> //memcpy
#include <type_traits> //is_same, integral_contant, enable_if, etc
#include <utility> //forward
#include <tuple>

namespace raii{

	class string_expr{};
	class string_base;

	namespace detail{
		std::true_type is_string_helper(string_expr);
		std::false_type is_string_helper(...);
		template<class T>
		struct is_string{
			static constexpr bool value = std::is_same<std::true_type,decltype(is_string_helper(std::declval<T>()))>::value;
		};
		std::true_type is_string_base(string_base*);
		std::false_type is_string_base(...);
		template<class T>
		struct is_concrete_string{
			static constexpr bool value = std::is_same<std::true_type,decltype(is_string_base(std::declval<typename std::decay<T>::type*>()))>::value;
		};
		template<class... Args>
		std::true_type is_tuple_helper(std::tuple<Args...>);
		std::false_type is_tuple_helper(...);
		template<class T>
		struct is_tuple{
			static constexpr bool value = std::is_same<std::true_type,decltype(is_tuple_helper(std::declval<T>()))>::value;
		};
	}



	//Base of all RAII strings. Its use is allowing passing of raii strings to functions without knowing the exact type
	class string_base : public string_expr
	{
	protected:
		size_t m_length = 0;
		char* m_data = nullptr;

	protected:
		constexpr string_base(void) = default;
		//Initialize without copying
		constexpr string_base(char* data, size_t len):
			m_length(len), m_data(data){}
		//Allocate without assigning
		string_base(size_t len);
		//Copy ctor (do nothing)
		string_base(const string_base&){}

	public:
		virtual ~string_base(void) = default;

	public:
		//Copy from c string
		string_base& operator=(const char* c);
		//Copy from other string_base
		string_base& operator=(const string_base& s);
		//Move from other string base
		template<class T, typename std::enable_if<detail::is_string<T>::value && !detail::is_concrete_string<T>::value,void>::type* = nullptr>
		string_base& operator=(T&& t){
			size_t len = t.length();
			char* tmp;
			if(len > m_length){
				tmp = _allocate(len+1);
				_assign(tmp, t.get(), 0);
				_free(m_data);
			}else{
				tmp = m_data;
				_assign(tmp, t.get(), 0);
			}
			m_data = tmp;
			m_data[len] = 0;
			m_length = len;
			return *this;
		}
		//Replace managed pointer. Frees existing value
		void reset(char* val = nullptr);
		//Stop managing stored pointer. Does not free.
		char* release(void);

		//Length of string not including null terminator
		constexpr size_t length(void)const{return m_length;}
		//direct access to managed pointer
		constexpr char* get(void){return m_data;}
		constexpr const char* get(void)const{return m_data;}
		operator char*(void);
		operator const char*(void)const;
		//true if m_data is not null
		operator bool(void)const;

		char& operator[](size_t i);
		const char& operator[](size_t i)const;

	protected:
		string_base& _copy_string(const char* s, size_t len);
		template<class Tup, size_t I = 0>
		static void _assign(char* dest, Tup&& t, size_t offset){
			memcpy(dest+offset, std::get<I>(t), std::get<I+1>(t));
			if constexpr(I+2 < std::tuple_size<Tup>::value){
				_assign<Tup,I+2>(dest, std::forward<Tup>(t), offset+std::get<I+1>(t));
			}
		}
	private:
		virtual char* _allocate(size_t)const = 0;
		virtual void _free(char*)const = 0;
		virtual char* _copy(const char*, size_t)const = 0;
	};



	//Supplies all functions that string_base can't implement
	template<class Allocator>
	class string_intermediary : public string_base
	{
	public:
		using allocator_type = Allocator;

	public:
		string_intermediary(void) = default;
		string_intermediary(char* data, size_t len):
			string_base(data, len){}
		string_intermediary(const char* data):
			string_base(strlen(data))
		{
			m_data = reinterpret_cast<char*>(Allocator::copy(data, m_length+1));
		}
		string_intermediary(size_t len):
			string_base(reinterpret_cast<char*>(Allocator::allocate(len+1)), len){}

		//normal copy and move ctors
		string_intermediary(const string_intermediary& b):
			string_base(reinterpret_cast<char*>(Allocator::copy(b.m_data, b.m_length+1)), b.m_length){}
		string_intermediary(string_intermediary&& s):
			string_base(std::exchange(s.m_data, nullptr), s.m_length){}

		string_intermediary(const string_base& b):
			string_base(reinterpret_cast<char*>(Allocator::copy(b.get(), b.length()+1)), b.length()){}

		//copy from string expression
		template<class T, typename std::enable_if<detail::is_string<T>::value && !detail::is_concrete_string<T>::value,void>::type* = nullptr>
		string_intermediary(T&& t){
			size_t len = t.length();

			char* tmp = reinterpret_cast<char*>(Allocator::allocate(len+1));
			_assign(tmp, t.get(), 0);
			m_data = tmp;
			m_data[len] = 0;
			m_length = len;
		}

		//dtor
		~string_intermediary(void){
			Allocator::free(m_data);
		}

		string_intermediary& operator=(const string_intermediary&) = default;
		string_intermediary& operator=(string_intermediary&& s){
			std::swap(m_data, s.m_data);
			m_length = s.m_length;
			return *this;
		}
		using string_base::operator=;


		string_intermediary operator+(const string_base& s)const{
			string_intermediary tmp(reinterpret_cast<char*>(Allocator::allocate(m_length + s.length() + 1)), m_length+s.length());
			memcpy(tmp.get(), m_data, m_length);
			strcpy(tmp.get()+m_length, s.get());
			return tmp;
		}

		string_intermediary operator+(const char* c)const{
			size_t len = strlen(c);
			string_intermediary tmp(reinterpret_cast<char*>(Allocator::allocate(m_length + len + 1)), m_length+len);
			memcpy(tmp.get(), m_data, m_length);
			strcpy(tmp.get()+m_length, c);
			return tmp;
		}

	private:
		char* _allocate(size_t len)const override final{
			return reinterpret_cast<char*>(Allocator::allocate(len));
		}
		void _free(char* ptr)const override final{
			Allocator::free(ptr);
		}
		char* _copy(const char* ptr, size_t len)const override final{
			return reinterpret_cast<char*>(Allocator::copy(ptr, len));
		}
	};



	//check for member function 'length'
	namespace detail{
		template<class T>
		struct has_len{
			template<class U, class V>
			struct check;

			template<class U>
			static std::true_type test(check<U,decltype(&U::length)>*);
			template<class U>
			static std::false_type test(...);

			static constexpr bool value = std::is_same<std::true_type,decltype(test<T>(0))>::value;
		};

	}



	//Like an expression template but not really
	template<class Left, class Right>
	class string_cat_expr : public string_expr
	{
	private:
		Left m_l;
		Right m_r;

	public:
		template<class T, class U>
		string_cat_expr(T&& l, U&& r):
			m_l(std::forward<Left>(l)),
			m_r(std::forward<Right>(r)){}
		string_cat_expr(const string_cat_expr& s):
			m_l(s.m_l),
			m_r(s.m_r){}
		string_cat_expr(string_cat_expr&& s):
			m_l(s.m_l),
			m_r(s.m_r){}

		size_t length(void)const{
			return _llen() + _rlen();
		}
		auto get(void){
			return std::tuple_cat(_lget(), _rget());
		}
	private:
		auto _lget(void){
			if constexpr(detail::is_string<Left>::value){
				if constexpr(detail::is_tuple<decltype(m_l.get())>::value){
					//string_cat_expr
					return m_l.get();
				}else{
					//string_base
					return std::make_tuple(m_l.get(), m_l.length());
				}
			}else{
				//c string
				return std::make_tuple(m_l, strlen(m_l));
			}
		}
		auto _rget(void){
			if constexpr(detail::is_string<Right>::value){
				if constexpr(detail::is_tuple<decltype(m_r.get())>::value){
					return m_r.get();
				}else{
					return std::make_tuple(m_r.get(), m_r.length());
				}
			}else{
				return std::make_tuple(m_r, strlen(m_r));
			}
		}
		size_t _llen(void)const{
			if constexpr(detail::has_len<typename std::remove_reference<Left>::type>::value){
				return m_l.length();
			}else{
				return strlen(m_l);
			}
		}
		size_t _rlen(void)const{
			if constexpr(detail::has_len<typename std::remove_reference<Right>::type>::value){
				return m_r.length();
			}else{
				return strlen(m_r);
			}
		}
	};

}

template<class Str1, class Str2, typename std::enable_if<raii::detail::is_concrete_string<Str1>::value&&raii::detail::is_concrete_string<Str2>::value,void>::type* = nullptr>
bool operator==(Str1&& left, Str2&& right){
	return left && right && left.length() == right.length() && !strcmp(left.get(), right.get());
}
template<class Str1, class Str2, typename std::enable_if<raii::detail::is_concrete_string<Str1>::value&&raii::detail::is_concrete_string<Str2>::value,void>::type* = nullptr>
bool operator!=(Str1&& left, Str2&& right){
	return !(left == right);
}

template<class Right, typename std::enable_if<raii::detail::is_string<Right>::value,void>::type* = nullptr>
auto operator+(const char* left, Right&& right){
	return raii::string_cat_expr<const char*,decltype(std::forward<Right>(right))>(left, std::forward<Right>(right));
}
template<class Left, typename std::enable_if<raii::detail::is_string<Left>::value,void>::type* = nullptr>
auto operator+(Left&& left, const char* right){
	return raii::string_cat_expr<decltype(std::forward<Left>(left)),const char*>(std::forward<Left>(left), right);
}
template<class Left, class Right, typename std::enable_if<raii::detail::is_string<Left>::value&&raii::detail::is_string<Right>::value,void>::type* = nullptr>
auto operator+(Left&& l, Right&& r){
	return raii::string_cat_expr<decltype(std::forward<Left>(l)),decltype(std::forward<Right>(r))>(std::forward<Left>(l), std::forward<Right>(r));
}
template<class Left, class Right, typename std::enable_if<raii::detail::is_string<Left>::value&&raii::detail::is_string<Right>::value,void>::type* = nullptr>
decltype(auto) operator+=(Left& l, Right&& r){
	return l = (l + std::forward<Right>(r));
}
template<class Left, typename std::enable_if<raii::detail::is_string<Left>::value,void>::type* = nullptr>
decltype(auto) operator+=(Left& l, const char* r){
	return l = (l + r);
}

#endif