sqlpp11/include/sqlpp11/select_column_list.h

/*
 * Copyright (c) 2013-2016, 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_SELECT_COLUMN_LIST_H
#define SQLPP_SELECT_COLUMN_LIST_H

#include <sqlpp11/data_types/no_value.h>
#include <sqlpp11/detail/copy_tuple_args.h>
#include <sqlpp11/detail/type_set.h>
#include <sqlpp11/dynamic_select_column_list.h>
#include <sqlpp11/expression_fwd.h>
#include <sqlpp11/field_spec.h>
#include <sqlpp11/interpret_tuple.h>
#include <sqlpp11/named_interpretable.h>
#include <sqlpp11/policy_update.h>
#include <sqlpp11/result_row.h>
#include <sqlpp11/select_pseudo_table.h>
#include <sqlpp11/table.h>
#include <tuple>

namespace sqlpp
{
  namespace detail
  {
    template <typename... Columns>
    struct select_traits
    {
      using _traits = make_traits<no_value_t, tag::is_select_column_list, tag::is_return_value>;
      struct _alias_t
      {
      };
    };

    template <typename Column>
    struct select_traits<Column>
    {
      using _traits = make_traits<value_type_of<Column>,
                                  tag::is_select_column_list,
                                  tag::is_return_value,
                                  tag::is_expression,
                                  tag::is_selectable>;
      using _alias_t = typename Column::_alias_t;
    };
  }

  // SELECTED COLUMNS DATA
  template <typename Database, typename... Columns>
  struct select_column_list_data_t
  {
    select_column_list_data_t(Columns... columns) : _columns(columns...)
    {
    }

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

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

    std::tuple<Columns...> _columns;
    dynamic_select_column_list<Database> _dynamic_columns;
  };

  SQLPP_PORTABLE_STATIC_ASSERT(
      assert_no_unknown_tables_in_selected_columns_t,
      "at least one selected column requires a table which is otherwise not known in the statement");
  SQLPP_PORTABLE_STATIC_ASSERT(assert_no_unknown_aggregates_t,
                               "not all selected columns are made of aggregates, despite group_by or similar");

  // SELECTED COLUMNS
  template <typename Database, typename... Columns>
  struct select_column_list_t
  {
    using _traits = typename detail::select_traits<Columns...>::_traits;
    using _nodes = detail::type_vector<Columns...>;

    using _alias_t = typename detail::select_traits<Columns...>::_alias_t;

    using _is_dynamic = is_database<Database>;

    struct _column_type
    {
    };

    // Data
    using _data_t = select_column_list_data_t<Database, Columns...>;

    // Member implementation with data and methods
    template <typename Policies>
    struct _impl_t
    {
      // workaround for msvc bug https://connect.microsoft.com/VisualStudio/Feedback/Details/2173269
      _impl_t() = default;
      _impl_t(const _data_t& data) : _data(data)
      {
      }

      template <typename NamedExpression>
      void add(NamedExpression namedExpression)
      {
        using named_expression = auto_alias_t<NamedExpression>;
        static_assert(_is_dynamic::value, "selected_columns::add() can only be called for dynamic_column");
        static_assert(is_selectable_t<named_expression>::value,
                      "invalid named expression argument in selected_columns::add()");
        static_assert(Policies::template _no_unknown_tables<named_expression>::value,
                      "named expression uses tables unknown to this statement in selected_columns::add()");
        using column_names = detail::make_type_set_t<typename Columns::_alias_t...>;
        static_assert(not detail::is_element_of<typename named_expression::_alias_t, column_names>::value,
                      "a column of this name is present in the select already");
        using _serialize_check = sqlpp::serialize_check_t<typename Database::_serializer_context_t, named_expression>;
        _serialize_check{};

        using ok =
            logic::all_t<_is_dynamic::value, is_selectable_t<named_expression>::value, _serialize_check::type::value>;

        _add_impl(namedExpression, ok());  // dispatch to prevent compile messages after the static_assert
      }

      // private:
      template <typename NamedExpression>
      void _add_impl(NamedExpression namedExpression, const std::true_type&)
      {
        return _data._dynamic_columns.emplace_back(auto_alias_t<NamedExpression>{namedExpression});
      }

      template <typename NamedExpression>
      void _add_column_impl(NamedExpression namedExpression, const std::false_type&);

    public:
      _data_t _data;
    };

    // Base template to be inherited by the statement
    template <typename Policies>
    struct _base_t
    {
      using _data_t = select_column_list_data_t<Database, Columns...>;

      // workaround for msvc bug https://connect.microsoft.com/VisualStudio/Feedback/Details/2173269
      template <typename... Args>
      _base_t(Args&&... args) : selected_columns{std::forward<Args>(args)...}
      {
      }

      _impl_t<Policies> selected_columns;
      _impl_t<Policies>& operator()()
      {
        return selected_columns;
      }
      const _impl_t<Policies>& operator()() const
      {
        return selected_columns;
      }

      _impl_t<Policies>& get_selected_columns()
      {
        return selected_columns;
      }
      const _impl_t<Policies>& get_selected_columns() const
      {
        return selected_columns;
      }

      template <typename T>
      static auto _get_member(T t) -> decltype(t.selected_columns)
      {
        return t.selected_columns;
      }

      using _table_check = typename std::conditional<Policies::template _no_unknown_tables<select_column_list_t>::value,
                                                     consistent_t,
                                                     assert_no_unknown_tables_in_selected_columns_t>::type;

      using _aggregate_check = typename std::conditional<Policies::template _no_unknown_aggregates<Columns...>::value,
                                                         consistent_t,
                                                         assert_no_unknown_aggregates_t>::type;

      using _consistency_check = detail::get_first_if<is_inconsistent_t, consistent_t, _table_check, _aggregate_check>;
    };

    // Result methods
    template <typename Statement>
    struct _result_methods_t
    {
      using _statement_t = Statement;

      const _statement_t& _get_statement() const
      {
        return static_cast<const _statement_t&>(*this);
      }

      template <typename Db, typename Column>
      struct _deferred_field_t
      {
        using type = make_field_spec_t<_statement_t, Column>;
      };

      template <typename Db, typename Column>
      using _field_t = typename _deferred_field_t<Db, Column>::type;

      template <typename Db>
      using _result_row_t = typename std::conditional<_is_dynamic::value,
                                                      dynamic_result_row_t<Db, _field_t<Db, Columns>...>,
                                                      result_row_t<Db, _field_t<Db, Columns>...>>::type;

      using _dynamic_names_t = typename dynamic_select_column_list<Database>::_names_t;

      template <typename AliasProvider>
      struct _deferred_table_t
      {
        using table = select_pseudo_table_t<_statement_t, Columns...>;
        using alias = typename table::template _alias_t<AliasProvider>;
      };

      template <typename AliasProvider>
      using _table_t = typename _deferred_table_t<AliasProvider>::table;

      template <typename AliasProvider>
      using _alias_t = typename _deferred_table_t<AliasProvider>::alias;

      template <typename AliasProvider>
      _alias_t<AliasProvider> as(const AliasProvider& aliasProvider) const
      {
        consistency_check_t<_statement_t>{};
        static_assert(_statement_t::_can_be_used_as_table(),
                      "statement cannot be used as table, e.g. due to missing tables");
        static_assert(logic::none_t<is_multi_column_t<Columns>::value...>::value,
                      "cannot use multi-columns in sub selects");
        return _table_t<AliasProvider>(_get_statement()).as(aliasProvider);
      }

      const _dynamic_names_t& get_dynamic_names() const
      {
        return _get_statement().get_selected_columns()._data._dynamic_columns._dynamic_expression_names;
      }

      size_t get_no_of_result_columns() const
      {
        return sizeof...(Columns) + _get_statement().get_selected_columns()._data._dynamic_columns.size();
      }

      // Execute
      template <typename Db, typename Composite>
      auto _run(Db& db, const Composite& composite) const -> result_t<decltype(db.select(composite)), _result_row_t<Db>>
      {
        return {db.select(composite), get_dynamic_names()};
      }

      template <typename Db>
      auto _run(Db& db) const -> result_t<decltype(db.select(std::declval<_statement_t>())), _result_row_t<Db>>
      {
        return {db.select(_get_statement()), get_dynamic_names()};
      }

      // Prepare
      template <typename Db, typename Composite>
      auto _prepare(Db& db, const Composite& composite) const -> prepared_select_t<Db, _statement_t, Composite>
      {
        return {make_parameter_list_t<Composite>{}, get_dynamic_names(), db.prepare_select(composite)};
      }

      template <typename Db>
      auto _prepare(Db& db) const -> prepared_select_t<Db, _statement_t>
      {
        return {make_parameter_list_t<_statement_t>{}, get_dynamic_names(), db.prepare_select(_get_statement())};
      }
    };
  };

  namespace detail
  {
    template <typename Database, typename... Columns>
    using make_select_column_list_t =
        copy_tuple_args_t<select_column_list_t, Database, decltype(column_tuple_merge(std::declval<Columns>()...))>;
  }

  SQLPP_PORTABLE_STATIC_ASSERT(assert_selected_colums_are_selectable_t, "selected columns must be selectable");
  template <typename... T>
  struct check_selected_columns
  {
    using type = static_combined_check_t<
        static_check_t<logic::all_t<(is_selectable_t<T>::value or is_multi_column_t<T>::value)...>::value,
                       assert_selected_colums_are_selectable_t>>;
  };
  template <typename... T>
  using check_selected_columns_t = typename check_selected_columns<T...>::type;

  struct no_select_column_list_t
  {
    using _traits = make_traits<no_value_t, tag::is_noop, tag::is_missing>;
    using _nodes = detail::type_vector<>;

    struct _alias_t
    {
    };

    // Data
    using _data_t = no_data_t;

    // Member implementation with data and methods
    template <typename Policies>
    struct _impl_t
    {
      // workaround for msvc bug https://connect.microsoft.com/VisualStudio/Feedback/Details/2173269
      _impl_t() = default;
      _impl_t(const _data_t& data) : _data(data)
      {
      }

      _data_t _data;
    };

    // Base template to be inherited by the statement
    template <typename Policies>
    struct _base_t
    {
      using _data_t = no_data_t;

      // workaround for msvc bug https://connect.microsoft.com/VisualStudio/Feedback/Details/2173269
      template <typename... Args>
      _base_t(Args&&... args) : no_selected_columns{std::forward<Args>(args)...}
      {
      }

      _impl_t<Policies> no_selected_columns;
      _impl_t<Policies>& operator()()
      {
        return no_selected_columns;
      }
      const _impl_t<Policies>& operator()() const
      {
        return no_selected_columns;
      }

      template <typename T>
      static auto _get_member(T t) -> decltype(t.no_selected_columns)
      {
        return t.no_selected_columns;
      }

      using _database_t = typename Policies::_database_t;

      template <typename... T>
      static constexpr auto _check_tuple(std::tuple<T...>) -> check_selected_columns_t<T...>
      {
        return {};
      }

      template <typename... T>
      static constexpr auto _check_args(T... args) -> decltype(_check_tuple(detail::column_tuple_merge(args...)))
      {
        return _check_tuple(detail::column_tuple_merge(args...));
      }

      template <typename Check, typename T>
      using _new_statement_t = new_statement_t<Check, Policies, no_select_column_list_t, T>;

      using _consistency_check = consistent_t;

      template <typename... Args>
      auto columns(Args... args) const
          -> _new_statement_t<decltype(_check_args(args...)), detail::make_select_column_list_t<void, Args...>>
      {
        static_assert(sizeof...(Args), "at least one selectable expression (e.g. a column) required in columns()");
        static_assert(decltype(_check_args(args...))::value,
                      "at least one argument is not a selectable expression in columns()");

        return _columns_impl<void>(decltype(_check_args(args...)){}, detail::column_tuple_merge(args...));
      }

      template <typename... Args>
      auto dynamic_columns(Args... args) const
          -> _new_statement_t<decltype(_check_args(args...)), detail::make_select_column_list_t<_database_t, Args...>>
      {
        static_assert(not std::is_same<_database_t, void>::value,
                      "dynamic_columns must not be called in a static statement");
        static_assert(decltype(_check_args(args...))::value,
                      "at least one argument is not a selectable expression in columns()");

        return _columns_impl<_database_t>(decltype(_check_args(args...)){}, detail::column_tuple_merge(args...));
      }

    private:
      template <typename Database, typename Check, typename... Args>
      auto _columns_impl(Check, std::tuple<Args...> args) const -> inconsistent<Check>;

      template <typename Database, typename... Args>
      auto _columns_impl(consistent_t, std::tuple<Args...> args) const
          -> _new_statement_t<consistent_t, select_column_list_t<Database, Args...>>
      {
        static_assert(not detail::has_duplicates<Args...>::value, "at least one duplicate argument detected");
        static_assert(not detail::has_duplicates<typename Args::_alias_t...>::value,
                      "at least one duplicate name detected");

        return {static_cast<const derived_statement_t<Policies>&>(*this),
                typename select_column_list_t<Database, Args...>::_data_t{args}};
      }
    };
  };

  // Interpreters
  template <typename Context, typename Database, typename... Columns>
  struct serializer_t<Context, select_column_list_data_t<Database, Columns...>>
  {
    using _serialize_check = serialize_check_of<Context, Columns...>;
    using T = select_column_list_data_t<Database, Columns...>;

    static Context& _(const T& t, Context& context)
    {
      interpret_tuple(t._columns, ',', context);
      if (sizeof...(Columns) and not t._dynamic_columns.empty())
        context << ',';
      serialize(t._dynamic_columns, context);
      return context;
    }
  };

  template <typename... T>
  auto select_columns(T&&... t) -> decltype(statement_t<void, no_select_column_list_t>().columns(std::forward<T>(t)...))
  {
    return statement_t<void, no_select_column_list_t>().columns(std::forward<T>(t)...);
  }

  template <typename Database, typename... T>
  auto dynamic_select_columns(const Database&, T&&... t)
      -> decltype(statement_t<Database, no_select_column_list_t>().dynamic_columns(std::forward<T>(t)...))
  {
    return statement_t<Database, no_select_column_list_t>().dynamic_columns(std::forward<T>(t)...);
  }
}

#endif