Deliver/include/Log4CPP/Common.Include/Utility.Expected.tlh

#pragma once

#include <system_error>
#include <memory>

#include "Utility.Either.tlh"
#include "Utility.Error.hpp"


//-----------------------------------------------------------------------------
//  Expected
//  与 C++ 23 的 std::expected 很像, 但是这里把错误类型固定成 Error::ErrorCode
//-----------------------------------------------------------------------------

namespace ECOM::Utility
{
	template <typename TV>
	struct Expected : public Either <TV, ECOM::Utility::Error::ErrorCode>
	{
		using base = Either <TV, ECOM::Utility::Error::ErrorCode>;

		using value_type = TV;
		using error_type = ECOM::Utility::Error::ErrorCode;

		template<class U>
		using rebind = Expected <U>;


		constexpr Expected () = delete;  // ! 不支持默认构造函数, 否则没法知道是左还是右 !

		//< 拷贝构造函数及移动构造函数
		constexpr Expected (Expected <TV> const & e) : base (e) {}
		constexpr Expected (Expected <TV> && e) : base (std::move (e)) {}
		//>

		//< 从 left 或 right 构造
		constexpr Expected (__tLeft  <value_type> const & _left ) : base (_left) {}
		constexpr Expected (__tRight <error_type> const & _right) : base (_right) {}

		constexpr Expected (__tLeft  <value_type> && _left ) : base (std::move (_left)) {}
		constexpr Expected (__tRight <error_type> && _right) : base (std::move (_right)) {}
		//>

		// 直接从 value 构造
		constexpr Expected (value_type const & _left) : base { _left } {}
		constexpr Expected (value_type && _left) : base { std::move (_left) } {}

		// 直接从 Error 构造
		constexpr Expected (error_type const & _right) : base { _right } {}
		constexpr Expected (error_type && _right) : base { std::move (_right) } {}


		constexpr bool isLeft  () const = delete;
		constexpr bool isRight () const = delete;

		constexpr bool isValue () const noexcept { return base::isLeft  (); }
		constexpr bool isError () const noexcept { return base::isRight (); }


		constexpr const value_type & getLeft  () const = delete;
		constexpr const error_type & getRight () const = delete;
		constexpr value_type & getLeft  () = delete;
		constexpr error_type & getRight () = delete;

		constexpr const value_type & value () const { return base::getLeft  (); }
		constexpr const error_type & error () const { return base::getRight (); }
		constexpr value_type & value () { return base::getLeft  (); }
		constexpr error_type & error () { return base::getRight (); }

	public:
		constexpr Expected & operator = (Expected <value_type> const & from)
		{
			base::operator = (from);
			return (*this);
		}

		constexpr Expected & operator = (Expected <value_type> && from)
		{
			base::operator = (std::move (from));
			return (*this);
		}

	public:
		constexpr static Expected make (value_type const & _left) { return Expected { _left }; }
		constexpr static Expected make (value_type && _left) { return Expected { std::move (_left) }; }

		constexpr static Expected make (error_type const & _right)
		{
			return Expected { _right };
		}

		constexpr static Expected make (error_type && _right)
		{
			return Expected { std::move (_right) };
		}

	};
}


//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------

//using eiResult  = ECOM::Utility::Either <int, ECOM::Utility::Error::ErrorCode>;
//using eiAck     = ECOM::Utility::Either <ECOM::Utility::iAck    , ECOM::Utility::Error::ErrorCode>;
//using eiBLOBAck = ECOM::Utility::Either <ECOM::Utility::iBLOBAck, ECOM::Utility::Error::ErrorCode>;

using eiResult  = ECOM::Utility::Expected <int>;

//< 最常用的返回值
constexpr auto eiSuccess = ECOM::Utility::left <int> (1);