/**
	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 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 REXY_STRING_BASE_HPP
#define REXY_STRING_BASE_HPP

#include <type_traits> //is_same, integral_contant, enable_if, etc
#include <utility> //forward
#include <cstddef> //size_t,ptrdiff
#include <cstring> //strlen
#include <climits> //CHAR_BIT

#include "steal.hpp"
#include "cx/utility.hpp"
#include "traits.hpp"
#include "expression.hpp"
#include "detail/string_appender.hpp"
#include "detail/hasallocator.hpp"

namespace rexy{

	//Base of all RAII strings. Its use is allowing passing of rexy strings to functions without knowing the exact type
	template<class Char>
	class string_base
	{
	public:
		using value_type = Char;
		using size_type = size_t;
		using difference_type = ptrdiff_t;
		using pointer = value_type*;
		using const_pointer = const value_type*;
		using reference = value_type&;
		using const_reference = const value_type&;
		using iterator = pointer;
		using const_iterator = const_pointer;

	private:
		static constexpr size_type EXTRA_SDATA_LEN = 0;

		struct ldata{
			unsigned char islong:1;
			size_type capacity:(CHAR_BIT*sizeof(size_type)-1);
			size_type length;
			constexpr ldata(void)noexcept:
				islong(0),
				capacity(0),
				length(0){}
		};

		static constexpr size_type MAX_SHORT_LEN = EXTRA_SDATA_LEN+sizeof(ldata)-2;
		struct sdata{
			unsigned char islong:1;
			unsigned char length:(CHAR_BIT-1);
			value_type data[MAX_SHORT_LEN+1];
			constexpr sdata(void)noexcept:
				islong(0),
				length(0),
				data{}{}
		};
		union combine_data{
			ldata l;
			sdata s;
			constexpr combine_data(void)noexcept:
				l(){}
		}m__data;
		pointer m_raw = m__data.s.data;

	protected:
		constexpr void set_islong_flag(bool b){
			if(b)
				m__data.l.islong = b;
			else
				m__data.s.islong = b;
		}
		constexpr bool islong(void)const{
			//common standard layout union member subsequence, never undefined behavior
			return m__data.l.islong;
		}
		constexpr pointer set_short_ptr(void){
			set_islong_flag(false);
			return m_raw = m__data.s.data;
		}
		constexpr pointer set_long_ptr(pointer ptr){
			set_islong_flag(true);
			return m_raw = ptr;
		}
		constexpr pointer get_long_ptr(void){
			return m_raw;
		}
		constexpr pointer get_short_ptr(void){
			return m_raw;
		}
		constexpr const_pointer get_long_ptr(void)const{
			return m_raw;
		}
		constexpr const_pointer get_short_ptr(void)const{
			return m_raw;
		}
		constexpr pointer get_pointer(void){
			return m_raw;
		}
		constexpr const_pointer get_pointer(void)const{
			return m_raw;
		}
		constexpr void set_long_length(size_type len){
			m__data.l.length = len;
		}
		constexpr size_type get_long_length(void)const{
			return m__data.l.length;
		}
		constexpr void set_short_length(size_type len){
			m__data.s.length = static_cast<unsigned char>(len);
		}
		constexpr size_type get_short_length(void)const{
			return m__data.s.length;
		}
		constexpr void set_long_capacity(size_type cap){
			m__data.l.capacity = cap;
		}
		constexpr void set_short_capacity(size_type){}
		constexpr size_type get_long_capacity(void)const{
			return m__data.l.capacity;
		}
		constexpr size_type get_short_capacity(void)const{
			return MAX_SHORT_LEN;
		}
		constexpr void set_length(size_type s){
			if(islong())
				set_long_length(s);
			else
				set_short_length(s);
		}

	protected:
		constexpr string_base(void)noexcept = default;
		//Initialize without copying
		constexpr string_base(pointer data, size_type len, size_type cap)noexcept{
			if(cap > MAX_SHORT_LEN){
				set_islong_flag(true);
				set_long_ptr(data);
				set_long_length(len);
				set_long_capacity(cap);
			}else if(len){
				set_islong_flag(false);
				pointer raw = set_short_ptr();
				if(len)
					memcpy(raw, data, sizeof(value_type)*len);
				raw[len] = 0;
				set_short_length(len);
				set_short_capacity(cap);
			}
		}
		constexpr string_base(pointer data, size_type len)noexcept:
			string_base(data, len, len){}
		//Copy ctor, copy length+capacity+short string, not long string value
		constexpr string_base(const string_base& s)noexcept:
			m__data(s.m__data){}
		constexpr string_base(string_base&& s)noexcept:
			m__data(std::move(s.m__data)),
			m_raw(s.islong() ? s.m_raw : m__data.s.data)
		{
			s.set_islong_flag(false);
		}
		~string_base(void)noexcept = default;

		constexpr string_base& operator=(string_base&& s)noexcept{
			std::swap(m__data, s.m__data);
			if(this->islong())
				std::swap(m_raw, s.m_raw);
			else{
				s.m_raw = m_raw;
				m_raw = m__data.s.data;
			}
			return *this;
		}

	public:
		//Length of string not including null terminator
		constexpr size_type length(void)const noexcept{
			if(islong())
				return get_long_length();
			else
				return get_short_length();
		}
		constexpr size_type capacity(void)const noexcept{
			if(islong())
				return get_long_capacity();
			else
				return get_short_capacity();
		}
		//direct access to managed pointer
		constexpr pointer c_str(void)noexcept{return get_pointer();}
		constexpr const_pointer c_str(void)const noexcept{return get_pointer();}
		constexpr pointer get(void)noexcept{return get_pointer();}
		constexpr const_pointer get(void)const noexcept{return get_pointer();}
		constexpr operator pointer(void)noexcept{return get_pointer();}
		constexpr operator const_pointer(void)const noexcept{return get_pointer();}
		//true if m_data is not empty
		constexpr bool valid(void)const noexcept{return length() > 0;}

		constexpr int compare(const string_base& s)const{return cx::strcmp(get(), s.get());}
		constexpr int compare(const_pointer s)const{return cx::strcmp(get(), s);}

		constexpr reference operator[](size_type i)noexcept{return get_pointer()[i];}
		constexpr const_reference operator[](size_type i)const noexcept{return get_pointer()[i];}

		static constexpr bool uses_sso(void){return true;}
		static constexpr size_type short_string_size(void){return MAX_SHORT_LEN;}
	};


	//Supplies all functions that string_base can't implement
	template<class Char, class Allocator>
	class basic_string : protected detail::hasallocator<Allocator>, public string_base<Char>
	{
	public:
		using value_type = typename string_base<Char>::value_type;
		using size_type = typename string_base<Char>::size_type;
		using difference_type = typename string_base<Char>::difference_type;
		using pointer = typename string_base<Char>::pointer;
		using const_pointer = typename string_base<Char>::const_pointer;
		using reference = typename string_base<Char>::reference;
		using const_reference = typename string_base<Char>::const_reference;
		using iterator = typename string_base<Char>::iterator;
		using const_iterator = typename string_base<Char>::const_iterator;
		using allocator_type = Allocator;

	private:
		void _copy_construct_string(const_pointer data, size_type len, size_type cap)
			noexcept(noexcept(this->allocate(0)));
		basic_string& _copy_string(const_pointer s, size_type len)
			noexcept(noexcept(this->allocate(0)) &&
			         noexcept(this->deallocate(nullptr,0)));

	public:
		constexpr basic_string(void)noexcept;
		constexpr basic_string(rexy::steal<pointer> data, size_type len)noexcept;
		constexpr basic_string(rexy::steal<pointer> data, size_type len, size_type cap)noexcept;
		constexpr basic_string(rexy::steal<pointer> data)noexcept;
		basic_string(const_pointer data, size_type len)noexcept(noexcept(this->allocate(0)));
		basic_string(const_pointer data, size_type len, size_type cap)noexcept(noexcept(this->allocate(0)));
		basic_string(const_pointer data)noexcept(noexcept(this->allocate(0)));
		explicit basic_string(size_type len)noexcept(noexcept(this->allocate(0)));
		basic_string(size_type len, size_type cap)noexcept(noexcept(this->allocate(0)));

		//normal copy and move ctors
		basic_string(const basic_string& b)noexcept(noexcept(this->allocate(0)));
		constexpr basic_string(basic_string&& s)noexcept;
		basic_string(const string_base<Char>&)noexcept(noexcept(this->allocate(0)));

		//dtor
		~basic_string(void)noexcept(noexcept(this->deallocate(nullptr, 0)));

		basic_string& operator=(const basic_string& s)
			noexcept(noexcept(this->allocate(0)) &&
			         noexcept(this->deallocate(nullptr,0)));

		constexpr basic_string& operator=(basic_string&& s)noexcept;

		basic_string& operator=(const string_base<Char>& s)
			noexcept(noexcept(this->allocate(0)) &&
			         noexcept(this->deallocate(nullptr,0)));
		//Copy from c string
		basic_string& operator=(const_pointer c)
			noexcept(noexcept(this->allocate(0)) &&
			         noexcept(this->deallocate(nullptr,0)));

		//Replace managed pointer. Frees existing value
		void reset(pointer val = nullptr)noexcept(noexcept(this->deallocate(nullptr,0)));
		void reset(pointer val, size_type len)noexcept(noexcept(this->deallocate(nullptr,0)));
		bool resize(size_type newsize)
			noexcept(noexcept(this->allocate(0)) &&
			         noexcept(this->deallocate(nullptr,0)));

		void append(const_pointer data, size_type len)
			noexcept(noexcept(this->allocate(0)) &&
			         noexcept(this->deallocate(nullptr,0)));
		void append(const_pointer data)
			noexcept(noexcept(this->allocate(0)) &&
			         noexcept(this->deallocate(nullptr,0)));
		pointer release(void)noexcept(noexcept(this->allocate(0)));
		using detail::hasallocator<Allocator>::allocator;
	};

	//Like an expression template but not really
	template<class Left, class Right>
	class string_cat_expr : public rexy::binary_expression<Left,Right>
	{
	static_assert(std::is_same<typename std::decay_t<Left>::value_type,typename std::decay_t<Right>::value_type>::value);
	private:
		using left_t = std::decay_t<Left>;
		using right_t = std::decay_t<Right>;
	public:
		using value_type = typename left_t::value_type;
		using size_type = decltype(typename left_t::size_type{0} + typename right_t::size_type{0});
		using difference_type = decltype(typename left_t::difference_type{0} - typename right_t::difference_type{0});
		using pointer = value_type*;
		using const_pointer = const value_type*;
		using reference = value_type&;
		using const_reference = const value_type&;
		using iterator = value_type*;
		using const_iterator = const value_type*;

	public:
		using binary_expression<Left,Right>::binary_expression;

		constexpr string_cat_expr(const string_cat_expr&) = default;
		constexpr string_cat_expr(string_cat_expr&&) = default;

		constexpr size_type length(void)const noexcept;
		template<class Alloc>
		operator basic_string<value_type,Alloc>(void)
			noexcept(std::is_nothrow_constructible<basic_string<value_type,Alloc>, typename basic_string<value_type,Alloc>::size_type>::value &&
			         std::is_nothrow_invocable<detail::string_appender<basic_string<value_type,Alloc>>,decltype(*this)>::value);
	};
	template<class Left, class Right>
	string_cat_expr(Left&&,Right&&) -> string_cat_expr<Left&&,Right&&>;

	template<class Char>
	class static_string : public string_base<Char>
	{
	public:
		using value_type = typename string_base<Char>::value_type;
		using size_type = typename string_base<Char>::size_type;
		using difference_type = typename string_base<Char>::difference_type;
		using pointer = typename string_base<Char>::pointer;
		using const_pointer = typename string_base<Char>::const_pointer;
		using reference = typename string_base<Char>::reference;
		using const_reference = typename string_base<Char>::const_reference;
		using iterator = typename string_base<Char>::iterator;
		using const_iterator = typename string_base<Char>::const_iterator;

	public:
		constexpr static_string(void)noexcept;
		constexpr static_string(const_pointer str, size_type len)noexcept;
		constexpr static_string(const_pointer c)noexcept;
		constexpr static_string(const static_string& s)noexcept;
		constexpr static_string(static_string&& s)noexcept;
		~static_string(void)noexcept = default;

		constexpr static_string& operator=(const_pointer c)noexcept;
		constexpr static_string& operator=(const static_string& s)noexcept;
		constexpr static_string& operator=(static_string&&)noexcept;
	};


	template<class T>
	struct is_string{
		static constexpr bool value = rexy::is_template_derived_type<T,string_base>::value || rexy::is_template_type<T,string_cat_expr>::value;
	};
	template<class T>
	struct is_concrete_string{
		static constexpr bool value = rexy::is_template_derived_type<T,string_base>::value;
	};
	namespace detail{

		template<class... Ts>
		using enable_if_string = std::enable_if_t<(is_string<Ts>::value && ...),int>;
		template<class... Ts>
		using enable_if_concrete_string = std::enable_if_t<(is_concrete_string<Ts>::value && ...),int>;
		template<class... Ts>
		using enable_if_expr_string = std::enable_if_t<(rexy::is_template_type<Ts,string_cat_expr>::value && ...),int>;

	} //namespace detail

	template<class Str1, class Str2, detail::enable_if_concrete_string<Str1,Str2> = 0>
	constexpr bool operator==(Str1&& left, Str2&& right)noexcept{
		return left.valid() && right.valid() && left.length() == right.length() && !cx::strcmp(left.get(), right.get());
	}
	template<class Str1, class Str2, detail::enable_if_concrete_string<Str1,Str2> = 0>
	constexpr bool operator!=(Str1&& left, Str2&& right)noexcept{
		return !(left == right);
	}

	template<class Left, class Right, detail::enable_if_string<Left,Right> = 0>
	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<class Right, detail::enable_if_string<Right> = 0>
	constexpr auto operator+(const char* left, Right&& right)
		noexcept(noexcept(::new (nullptr) string_cat_expr(rexy::static_string<char>(left), std::forward<Right>(right))))
	{
		return string_cat_expr(rexy::static_string<char>(left), std::forward<Right>(right));
	}

	template<class Left, detail::enable_if_string<Left> = 0>
	constexpr auto operator+(Left&& left, const char* right)
		noexcept(noexcept(::new (nullptr) string_cat_expr(std::forward<Left>(left), rexy::static_string<char>(right))))
	{
		return rexy::string_cat_expr(std::forward<Left>(left), rexy::static_string<char>(right));
	}

	template<class Left, class Right, detail::enable_if_concrete_string<Left> = 0, detail::enable_if_string<Right> = 0>
	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<class Left, detail::enable_if_concrete_string<Left> = 0>
	decltype(auto) operator+=(Left& l, const char* r)
		noexcept(noexcept(l + r) && std::is_nothrow_assignable<Left, decltype(l + r)>::value)
	{
		return l = (l + r);
	}
}

#include "string_base.tpp"

namespace{
	constexpr inline rexy::static_string<char> operator"" _ss(const char* str, size_t len)noexcept{
		return rexy::static_string<char>(str, len);
	}
	constexpr inline rexy::static_string<wchar_t> operator"" _ss(const wchar_t* str, size_t len)noexcept{
		return rexy::static_string<wchar_t>(str, len);
	}
	constexpr inline rexy::static_string<char16_t> operator"" _ss(const char16_t* str, size_t len)noexcept{
		return rexy::static_string<char16_t>(str, len);
	}
	constexpr inline rexy::static_string<char32_t> operator"" _ss(const char32_t* str, size_t len)noexcept{
		return rexy::static_string<char32_t>(str, len);
	}

}

#ifdef REXY_BINARY_BASE_HPP
#include "detail/binary_string_conv.hpp"
#endif
#ifdef REXY_CX_HASH_HPP
#include "cx/static_string_hash.hpp"
#endif

#endif