sqlpp11/include/sqlpp11/multi_column.h

/*
 * Copyright (c) 2013-2014, 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_MULTI_COLUMN_H
#define SQLPP_MULTI_COLUMN_H

#include <sqlpp11/no_value.h>
#include <sqlpp11/detail/logic.h>
#include <sqlpp11/detail/type_set.h>

#include <sqlpp11/detail/copy_tuple_args.h>

namespace sqlpp
{
	template<typename AliasProvider, typename... Columns>
		struct multi_column_alias_t;

	template<typename Unused, typename... Columns>
		struct multi_column_t
		{
			using _traits = make_traits<no_value_t>;
			using _recursive_traits = make_recursive_traits<Columns...>;

			static_assert(detail::all_t<is_named_expression_t<Columns>::value...>::value, "multi_column parameters need to be named expressions");

			multi_column_t(std::tuple<Columns...> columns):
				_columns(columns)
			{}

			multi_column_t(Columns... columns):
				_columns(columns...)
			{}

			multi_column_t(const multi_column_t&) = default;
			multi_column_t(multi_column_t&&) = default;
			multi_column_t& operator=(const multi_column_t&) = default;
			multi_column_t& operator=(multi_column_t&&) = default;
			~multi_column_t() = default;

			template<typename AliasProvider>
				multi_column_alias_t<AliasProvider, Columns...> as(const AliasProvider&)
				{
					return { *this };
				}


			using _value_type = no_value_t;
			using _is_multi_column = std::true_type;

			std::tuple<Columns...> _columns;
		};

	template<typename AliasProvider, typename... Columns>
		struct multi_column_alias_t
		{
			using _traits = make_traits<no_value_t, tag::is_alias, tag::is_multi_column, tag::is_named_expression>;
			using _recursive_traits = make_recursive_traits<Columns...>;

			static_assert(detail::all_t<is_named_expression_t<Columns>::value...>::value, "multi_column parameters need to be named expressions");

			using _name_t = typename AliasProvider::_name_t;

			multi_column_alias_t(multi_column_t<void, Columns...> multi_column):
				_columns(multi_column._columns)
			{}

			multi_column_alias_t(std::tuple<Columns...> columns):
				_columns(columns)
			{}

			multi_column_alias_t(Columns... columns):
				_columns(columns...)
			{}

			multi_column_alias_t(const multi_column_alias_t&) = default;
			multi_column_alias_t(multi_column_alias_t&&) = default;
			multi_column_alias_t& operator=(const multi_column_alias_t&) = default;
			multi_column_alias_t& operator=(multi_column_alias_t&&) = default;
			~multi_column_alias_t() = default;

			struct _value_type: public no_value_t
			{
				using _is_named_expression = std::true_type;
			};
			using _is_multi_column = std::true_type;

			std::tuple<Columns...> _columns;
		};

	template<typename Context, typename... Columns>
		struct serializer_t<Context, multi_column_t<void, Columns...>>
		{
			using T = multi_column_t<void, Columns...>;

			static void _(const T& t, Context& context)
			{
				static_assert(wrong_t<serializer_t>::value, "multi_column must be used with an alias");
			}
		};

	template<typename Context, typename AliasProvider, typename... Columns>
		struct serializer_t<Context, multi_column_alias_t<AliasProvider, Columns...>>
		{
			using T = multi_column_alias_t<AliasProvider, Columns...>;

			static Context& _(const T& t, Context& context)
			{
				interpret_tuple(t._columns, ',', context);
				return context;
			}
		};

	namespace detail
	{
		template<typename... Columns>
			using make_multi_column_t = 
			detail::copy_tuple_args_t<multi_column_t, void, 
			decltype(std::tuple_cat(detail::as_tuple<Columns>::_(std::declval<Columns>())...))>;
	}

	template<typename... Columns>
		auto multi_column(Columns... columns)
		-> detail::make_multi_column_t<Columns...>
		{
			return detail::make_multi_column_t<Columns...>(std::tuple_cat(detail::as_tuple<Columns>::_(columns)...));
		}


}

#endif