sqlpp11/include/sqlpp11/tvin.h

/*
 * Copyright (c) 2013-2015, Roland Bock
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 * 
 *   Redistributions of source code must retain the above copyright notice, this
 *   list of conditions and the following disclaimer.
 * 
 *   Redistributions in binary form must reproduce the above copyright notice, this
 *   list of conditions and the following disclaimer in the documentation and/or
 *   other materials provided with the distribution.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef SQLPP_TVIN_H
#define SQLPP_TVIN_H

// TVIN: Trivial value is NULL

#include <sqlpp11/type_traits.h>
#include <sqlpp11/serialize.h>
#include <sqlpp11/serializer.h>
#include <sqlpp11/wrap_operand.h>

namespace sqlpp
{
	template<typename Operand>
		struct tvin_arg_t
		{
			using _traits = make_traits<value_type_of<Operand>, tag::is_expression>;
			using _nodes = detail::type_vector<Operand>;

			using _operand_t = Operand;

			tvin_arg_t(_operand_t operand): 
				_value(operand)
			{}
			tvin_arg_t(const tvin_arg_t&) = default;
			tvin_arg_t(tvin_arg_t&&) = default;
			tvin_arg_t& operator=(const tvin_arg_t&) = default;
			tvin_arg_t& operator=(tvin_arg_t&&) = default;
			~tvin_arg_t() = default;

			_operand_t _value;
		};

	struct assert_tvin_with_correct_operator_t
	{
		using type = std::false_type;

		template<typename T = void>
		static void _()
		{
			static_assert(wrong_t<T>::value, "tvin may only be used with operators =, == and !=");
		}
	};

	template<typename Context, typename Operand>
		struct serializer_t<Context, tvin_arg_t<Operand>>
		{
			using _serialize_check = assert_tvin_with_correct_operator_t;
			using T = tvin_arg_t<Operand>;

			static Context& _(const T& t, Context& context)
			{
				_serialize_check::_();
			}
		};

	template<typename T>
		struct tvin_t;

	namespace detail
	{
	template<typename T>
		struct allow_tvin_impl
		{
			using type = T;
		};
	template <typename T>
		struct allow_tvin_impl<tvin_arg_t<T>>
		{
			using type = tvin_t<T>;
		};
	}
	template<typename T>
		using allow_tvin_t = typename detail::allow_tvin_impl<T>::type;

	template<typename Operand>
		struct tvin_t
		{
			using _traits = make_traits<value_type_of<Operand>, tag::is_expression>;
			using _nodes = detail::type_vector<Operand>;

			using _operand_t = Operand;

			tvin_t(tvin_arg_t<Operand> arg): 
				_value(arg._value)
			{}
			tvin_t(const tvin_t&) = default;
			tvin_t(tvin_t&&) = default;
			tvin_t& operator=(const tvin_t&) = default;
			tvin_t& operator=(tvin_t&&) = default;
			~tvin_t() = default;

			bool _is_trivial() const
			{
				return _value._is_trivial();
			}

			bool _is_null() const
			{
				return _value._is_trivial();
			}

			_operand_t _value;
		};

	namespace detail
	{
		template<typename T>
			struct is_tvin_impl
			{
				using type = std::false_type;
			};
		template<typename T>
			struct is_tvin_impl<tvin_t<T>>
			{
				using type = std::true_type;
			};
	}
	template<typename T>
		using is_tvin_t = typename detail::is_tvin_impl<T>::type;

	template<typename Context, typename Operand>
		struct serializer_t<Context, tvin_t<Operand>>
		{
			using _serialize_check = serialize_check_of<Context, Operand>;
			using T = tvin_t<Operand>;

			static Context& _(const T& t, Context& context)
			{
				if (t._is_trivial())
				{
					context << "NULL";
				}
				else
				{
					serialize(t._value, context);
				}
				return context;
			}
		};

	template<typename Operand>
		auto tvin(Operand operand) -> tvin_arg_t<wrap_operand_t<Operand>>
		{
			using _operand_t = wrap_operand_t<Operand>;
			static_assert(not std::is_same<_operand_t, Operand>::value or is_result_field_t<Operand>::value, "tvin() used with invalid type (only string and primitive types allowed)");
			return {{operand}};
		}

}

#endif