sqlpp11/include/sqlpp11/vendor/offset.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_OFFSET_H
#define SQLPP_OFFSET_H

#include <sqlpp11/type_traits.h>
#include <sqlpp11/vendor/policy_update.h>
#include <sqlpp11/detail/type_set.h>

namespace sqlpp
{
	namespace vendor
	{
		// OFFSET
		template<typename Offset>
			struct offset_t
			{
				using _traits = make_traits<no_value_t, ::sqlpp::tag::offset>;
				using _recursive_traits = make_recursive_traits<Offset>;

				static_assert(is_integral_t<Offset>::value, "offset requires an integral value or integral parameter");

				offset_t(Offset value):
					_value(value)
				{}

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

				template<typename Policies>
					struct _methods_t
					{
					};

				Offset _value;
			};

		template<typename Database>
			struct dynamic_offset_t
			{
				using _traits = make_traits<no_value_t, ::sqlpp::tag::offset>;
				using _recursive_traits = make_recursive_traits<>;

				dynamic_offset_t():
					_value(noop())
				{
				}

				template<typename Offset>
					dynamic_offset_t(Offset value):
						_initialized(true),
						_value(typename wrap_operand<Offset>::type(value))
				{
				}

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

				template<typename Policies>
					struct _methods_t
					{
						template<typename Offset>
							void set_offset(Offset value)
							{
								// FIXME: Make sure that Offset does not require external tables? Need to read up on SQL
								using arg_t = typename wrap_operand<Offset>::type;
								static_cast<typename Policies::_statement_t*>(this)->_offset._value = arg_t{value};
								static_cast<typename Policies::_statement_t*>(this)->_offset._initialized = true;
							}
					};

				bool _initialized = false;
				interpretable_t<Database> _value;
			};

		struct no_offset_t
		{
			using _traits = make_traits<no_value_t, ::sqlpp::tag::noop>;
			using _recursive_traits = make_recursive_traits<>;

			template<typename Policies>
				struct _methods_t
				{
					using _database_t = typename Policies::_database_t;
					template<typename T>
					using _new_statement_t = typename Policies::template _new_statement_t<no_offset_t, T>;

					template<typename Arg>
						auto offset(Arg arg)
						-> _new_statement_t<offset_t<typename wrap_operand<Arg>::type>>
						{
							return { *static_cast<typename Policies::_statement_t*>(this), offset_t<typename wrap_operand<Arg>::type>{{arg}} };
						}

					auto dynamic_offset()
						-> _new_statement_t<dynamic_offset_t<_database_t>>
						{
							static_assert(not std::is_same<_database_t, void>::value, "dynamic_offset must not be called in a static statement");
							return { *static_cast<typename Policies::_statement_t*>(this), dynamic_offset_t<_database_t>{} };
						}
				};
		};

		// Interpreters
		template<typename Context, typename Offset>
			struct serializer_t<Context, offset_t<Offset>>
			{
				using T = offset_t<Offset>;

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

		template<typename Context, typename Database>
			struct serializer_t<Context, dynamic_offset_t<Database>>
			{
				using T = dynamic_offset_t<Database>;

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

		template<typename Context>
			struct serializer_t<Context, no_offset_t>
			{
				using T = no_offset_t;

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

#endif