sqlpp11/include/sqlpp11/join.h

/*
 * Copyright (c) 2013, 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_JOIN_H
#define SQLPP_JOIN_H

#include <sqlpp11/type_traits.h>
#include <sqlpp11/on.h>

namespace sqlpp
{
	struct inner_join_t
	{
		template<typename Db>
			struct _is_supported 
			{ 
				static constexpr bool value = Db::_supports_inner_join; 
			};

		static constexpr const char* _name = " INNER ";
	};
	struct outer_join_t
	{
		template<typename Db>
			struct _is_supported 
			{ 
				static constexpr bool value = Db::_supports_outer_join; 
			};

		static constexpr const char* _name = " OUTER ";
	};
	struct left_outer_join_t
	{
		template<typename Db>
			struct _is_supported 
			{ 
				static constexpr bool value = Db::_supports_left_outer_join; 
			};

		static constexpr const char* _name = " LEFT OUTER ";
	};
	struct right_outer_join_t
	{
		template<typename Db>
			struct _is_supported 
			{ 
				static constexpr bool value = Db::_supports_right_outer_join; 
			};

		static constexpr const char* _name = " RIGHT OUTER ";
	};

	template<typename JoinType, typename Lhs, typename Rhs, typename On = noop>
	struct join_t
	{
		static_assert(is_table_t<Lhs>::value, "invalid lhs argument for join()");
		static_assert(is_table_t<Rhs>::value, "invalid rhs argument for join()");
		static_assert(is_noop<On>::value or is_on_t<On>::value, "invalid on expression in join().on()");

		static_assert(Lhs::_table_set::template is_disjunct_from<typename Rhs::_table_set>::value, "joined tables must not be identical");

		using _is_table = std::true_type;
		using _table_set = typename Lhs::_table_set::template join<typename Rhs::_table_set>::type;

		template<typename OnT> 
			using set_on_t = join_t<JoinType, Lhs, Rhs, OnT>;

		template<typename Expr>
			set_on_t<on_t<typename std::decay<Expr>::type>> on(Expr&& expr)
			{
				return { _lhs, _rhs, {std::forward<Expr>(expr)} };
			}

		template<typename T>
			join_t<inner_join_t, join_t, typename std::decay<T>::type> join(T&& t)
			{
				static_assert(not is_noop<On>::value, "join type requires on()");
				return { *this, std::forward<T>(t) };
			}

		template<typename T>
			join_t<inner_join_t, join_t, typename std::decay<T>::type> inner_join(T&& t)
			{
				static_assert(not is_noop<On>::value, "join type requires on()");
				return { *this, std::forward<T>(t) };
			}

		template<typename T>
			join_t<outer_join_t, join_t, typename std::decay<T>::type> outer_join(T&& t)
			{
				static_assert(not is_noop<On>::value, "join type requires on()");
				return { *this, std::forward<T>(t) };
			}

		template<typename T>
			join_t<left_outer_join_t, join_t, typename std::decay<T>::type> left_outer_join(T&& t)
			{
				static_assert(not is_noop<On>::value, "join type requires on()");
				return { *this, std::forward<T>(t) };
			}

		template<typename T>
			join_t<right_outer_join_t, join_t, typename std::decay<T>::type> right_outer_join(T&& t)
			{
				static_assert(not is_noop<On>::value, "join type requires on()");
				return { *this, std::forward<T>(t) };
			}

		template<typename Db>
			void serialize(std::ostream& os, Db& db) const
			{
				// FIXME: Need to check if db supports the join type. e.g. sqlite does not support right outer or full outer join
				static_assert(JoinType::template _is_supported<Db>::value, "join type not supported by current database");
				static_assert(not is_noop<On>::value, "joined tables require on()");
				_lhs.serialize(os, db);
				os << JoinType::_name;
			 	os << " JOIN ";
				_rhs.serialize(os, db);
				_on.serialize(os, db);
			}

		Lhs _lhs;
		Rhs _rhs;
		On _on;
	};
}

#endif