FeatureList.hh

/*
 * Copyright (C) 2018 Open Source Robotics Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
*/

#ifndef GZ_PHYSICS_FEATURELIST_HH_
#define GZ_PHYSICS_FEATURELIST_HH_

#include <tuple>

#include <gz/physics/Feature.hh>

#if defined(_MSC_VER)
#pragma warning(push)
/// Suppress warnings about "base-class is already a base-class"
/// Typically, this would indicate a diamond pattern in inheritance,
/// but there are uses in the plugin mechanism recursive templates.
/// The templates have no base classes, so there are no ambiguity
/// concerns, so we can safely suppress the warning here.
#pragma warning(disable: 4584)
#endif  // defined(_MSC_VER)

namespace gz
{
  namespace physics
  {
    namespace detail
    {
      // Forward declarations
      template <typename...> struct CombineLists;
      template <bool, typename...> struct SelfConflict;
      template <typename> struct IterateTuple;
    }

    /////////////////////////////////////////////////
    /// \brief Use a FeatureList to aggregate a list of Features.
    ///
    /// FeatureLists can be constructed in hierarchies, e.g. a FeatureList can
    /// be passed into another FeatureList, and the set of all features in the
    /// new list will be the sum.
    ///
    /// \code
    /// // FeatureA, FeatureB, AdvancedA, and AdvancedB are all feature classes.
    ///
    /// using BasicList = FeatureList<FeatureA, FeatureB>;
    /// using AdvancedList = FeatureList<BasicList, AdvancedA, AdvancedB>;
    /// \endcode
    template <typename... FeaturesT>
    struct FeatureList : detail::IterateTuple<std::tuple<FeaturesT...>>
    {
      /// Features is a std::tuple containing all the feature classes that are
      /// bundled in this list. This list is fully seralialized; any hierarchy
      /// that was used to construct this FeatureList will be collapsed in this
      /// member.
      public: using Features =
          typename detail::CombineLists<FeaturesT...>::Result;

      public: using FeatureTuple = std::tuple<FeaturesT...>;

      /// \brief A static constexpr function which indicates whether a given
      /// Feature, F, is contained in this list.
      /// \tparam F
      ///   The feature class to check for in this FeatureList
      /// \return true if F is in this FeatureList; false otherwise.
      public: template <typename F>
      static constexpr bool HasFeature();

      /// \brief A static constexpr function which indicates whether any
      /// features in SomeFeatureList conflict with any features in
      /// SomeFeatureList.
      ///
      /// \tparam SomeFeatureList
      ///   The list to compare against for conflicts.
      /// \tparam AssertNoConflict
      ///   Setting this to true will result in a static_assert if a conflict is
      ///   found. That way, if a conflict exists, you will get a compilation
      ///   error, and the compilation error will tell you which feature is
      ///   conflicting.
      /// \return true if any features in SomeFeatureList conflict with this
      /// list or vice versa.
      public: template <typename SomeFeatureList,
                        bool AssertNoConflict = false>
      static constexpr bool ConflictsWith();

      /// \brief All the features required by this FeatureList will be included
      /// in CombineLists.
      public: using RequiredFeatures = void;

      // Check that this FeatureList does not contain any self-conflicts.
      static_assert(!detail::SelfConflict<true, FeaturesT...>::value,
          "FeatureList ERROR: YOUR LIST CONTAINS CONFLICTING FEATURES!");
    };

    /////////////////////////////////////////////////
    /// \brief If your feature is known to conflict with any other feature, then
    /// you should have your feature class inherit FeatureWithConflicts<...>,
    /// and pass it a list of the features that it conflicts with.
    template <typename... ConflictingFeatures>
    struct FeatureWithConflicts;

    /////////////////////////////////////////////////
    /// \brief If your feature is known to require any other features, then you
    /// should have your feature class inherit FeatureWithRequirements<...>,
    /// and pass it a list of the features that it requires.
    template <typename... RequiredFeatures>
    struct FeatureWithRequirements;
  }
}

#include <gz/physics/detail/FeatureList.hh>

#if defined(_MSC_VER)
#pragma warning(pop)
#endif  // defined(_MSC_VER)
#endif  // GZ_PHYSICS_FEATURELIST_HH_