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#ifndef DART_COMMON_DETAIL_COMPOSITEDATA_HPP_
#define DART_COMMON_DETAIL_COMPOSITEDATA_HPP_

#include <map>
#include <typeindex>
#include <typeinfo>
#include <unordered_set>

#include <Eigen/Core>

#include "dart/common/Aspect.hpp"

namespace dart {
namespace common {
namespace detail {

//==============================================================================
// This default template definition will be called when AspectOrComposite is
// an Aspect.
template <class AspectOrComposite, bool isAspect>
struct GetAspectImpl
{
  using Type = AspectOrComposite;
};

//==============================================================================
// This template specialization will be called when AspectOrComposite is not
// an Aspect (and is presumably a composite that defines a nested Aspect type).
template <class AspectOrComposite>
struct GetAspectImpl<AspectOrComposite, false>
{
  // If you get a compiler error that leads you here, then you are trying to
  // ask for the Aspect of an object that is not associated with any Aspect.
  // That means it does not define a nested Aspect type (such as how
  // RevoluteJoint defines the RevoluteJoint::Aspect).
  //
  // Whatever function is leading to the error must be given a template type
  // that either defines a nested type with the name Aspect, or else inherits
  // from the type dart::common::Aspect.
  using Type = typename AspectOrComposite::Aspect;
};

//==============================================================================
template <class AspectT>
struct GetAspect
{
  using Type =
      typename GetAspectImpl<AspectT, std::is_base_of<Aspect, AspectT>::value>::
          Type;
};

//==============================================================================
template <class AspectT>
struct GetState
{
  using Type = typename GetAspect<AspectT>::Type::State;
};

//==============================================================================
template <class AspectT>
struct GetProperties
{
  using Type = typename GetAspect<AspectT>::Type::Properties;
};

//==============================================================================
using CompositeStateMap
    = std::map<std::type_index, std::unique_ptr<Aspect::State>>;
using CompositePropertiesMap
    = std::map<std::type_index, std::unique_ptr<Aspect::Properties>>;

//==============================================================================
template <typename MapType, template <class> class GetData>
class CompositeData : public CloneableMap<MapType>
{
public:
  /// Forwarding constructor
  template <typename... Args>
  CompositeData(Args&&... args)
    : CloneableMap<MapType>(std::forward<Args>(args)...)
  {
    // Do nothing
  }

  virtual ~CompositeData() = default;

  /// Create (or replace) a piece of data in this
  template <class AspectT, typename... Args>
  typename GetData<AspectT>::Type& create(Args&&... args)
  {
    using Data = typename GetData<AspectT>::Type;
    using AspectType = typename GetAspect<AspectT>::Type;
    using DataType = typename GetData<Aspect>::Type;

    std::unique_ptr<DataType>& data = this->mMap[typeid(AspectType)]
        = std::make_unique<Data>(std::forward<Args>(args)...);
    return static_cast<Data&>(*data);
  }

  template <class AspectT>
  typename GetData<AspectT>::Type* get()
  {
    using Data = typename GetData<AspectT>::Type;
    using AspectType = typename GetAspect<AspectT>::Type;

    typename MapType::iterator it = this->mMap.find(typeid(AspectType));
    if (this->mMap.end() == it)
      return nullptr;

    return static_cast<Data*>(it->second.get());
  }

  template <class AspectT>
  const typename GetData<AspectT>::Type* get() const
  {
    return const_cast<CompositeData<MapType, GetData>*>(this)->get<AspectT>();
  }

  template <class AspectT, typename... Args>
  typename GetData<AspectT>::Type& getOrCreate(Args&&... args)
  {
    using Data = typename GetData<AspectT>::Type;
    using AspectType = typename GetAspect<AspectT>::Type;

    auto& it = this->mMap.insert(
        std::make_pair<std::type_index, std::unique_ptr<Data>>(
            typeid(AspectType), nullptr));

    const bool exists = !it.second;
    if (!exists)
      it.first = std::make_unique<Data>(std::forward<Args>(args)...);

    return static_cast<Data&>(*it.first);
  }

  template <class AspectT>
  bool has() const
  {
    return (get<AspectT>() != nullptr);
  }
};

//==============================================================================
using CompositeState = CompositeData<CompositeStateMap, GetState>;
using CompositeProperties
    = CompositeData<CompositePropertiesMap, GetProperties>;

//==============================================================================
template <
    class CompositeType,
    template <class>
    class GetData,
    typename... Aspects>
class ComposeData
{
public:
  ComposeData() = default;

  ComposeData(const CompositeType&)
  {
    // Do nothing
  }

  virtual ~ComposeData() = default;

  void setFrom(const CompositeType&)
  {
    // Do nothing
  }

protected:
  void _addData(CompositeType&) const
  {
    // Do nothing
  }
};

//==============================================================================
template <
    class CompositeType,
    template <class>
    class GetData,
    class AspectT,
    typename... Remainder>
struct ComposeData<CompositeType, GetData, AspectT, Remainder...>
  : public GetData<AspectT>::Type,
    public ComposeData<CompositeType, GetData, Remainder...>
{
public:
  enum DelegateTag
  {
    Delegate
  };

  using ThisClass = ComposeData<CompositeType, GetData, AspectT, Remainder...>;
  using Base = typename GetData<AspectT>::Type;
  using Data = typename Base::Data;
  using AspectType = typename GetAspect<AspectT>::Type;

  template <typename Arg>
  struct ConvertIfData
  {
    using Type = typename std::conditional<
        std::is_base_of<typename Base::Data, Arg>::value,
        typename Base::Data,
        Arg>::type;
  };

  template <typename Arg>
  struct ConvertIfComposite
  {
    using Type = typename std::conditional<
        std::is_base_of<CompositeType, Arg>::value,
        CompositeType,
        Arg>::type;
  };

  // To get byte-aligned Eigen vectors
  EIGEN_MAKE_ALIGNED_OPERATOR_NEW

  DART_DEFINE_ALIGNED_SHARED_OBJECT_CREATOR(ThisClass)

  ComposeData() = default;

  virtual ~ComposeData() = default;

  template <typename Arg1, typename... Args>
  ComposeData(const Arg1& arg1, const Args&... args)
    : ComposeData(
        Delegate,
        static_cast<const typename ConvertIfData<Arg1>::Type&>(arg1),
        args...)
  {
    // This constructor delegates
  }

  /// Grab relevant data out of a composite object
  ComposeData(const CompositeType& composite)
    : ComposeData<CompositeType, GetData, Remainder...>(composite)
  {
    _setBaseFrom(composite);
  }

  template <typename... Aspects>
  ComposeData(const ComposeData<CompositeType, GetData, Aspects...>& composite)
    : ComposeData(static_cast<const CompositeType&>(composite))
  {
    // This is a delegating constructor. If we get passed another ComposeData
    // object, then we convert it into a composite to ensure that we grab all
    // of its aspects.
  }

  // Dev Note: We must not use the argument 'composite' as a temporary, or else
  // it will get deleted when it reaches the last base constructor, preventing
  // any higher level constructors from calling _setBaseFrom(~) on it.
  ComposeData(CompositeType&& composite)
    : ComposeData(static_cast<const CompositeType&>(composite))
  {
    // This is a delegating constructor
  }

  operator CompositeType() const
  {
    CompositeType composite;
    _addData(composite);

    return composite;
  }

  void setFrom(const CompositeType& composite)
  {
    _setBaseFrom(composite);
    ComposeData<CompositeType, GetData, Remainder...>::setFrom(composite);
  }

  ComposeData& operator=(const CompositeType& composite)
  {
    setFrom(composite);
    return *this;
  }

  /// Grab any relevant data and copy it into this composite. Note that there
  /// will be NO compilation error, even if there is no relevant data in any of
  /// the arguments that get passed in. It will simply ignore all the arguments
  /// silently.
  template <typename... Args>
  void copy(const Args&... args)
  {
    _findData(args...);
  }

protected:
  template <typename... Args>
  ComposeData(DelegateTag, const Args&... args)
    : ComposeData<CompositeType, GetData, Remainder...>(args...)
  {
    // Pass all the arguments along to the next base class
  }

  template <typename... Args>
  ComposeData(DelegateTag, const Data& arg1, const Args&... args)
    : Base(arg1), ComposeData<CompositeType, GetData, Remainder...>(args...)
  {
    // Peel off the first argument and then pass along the rest
  }

  void _setBaseFrom(const CompositeType& composite)
  {
    const Base* data = composite.template get<AspectType>();
    if (data)
      static_cast<Base&>(*this) = *data;
  }

  void _addData(CompositeType& composite) const
  {
    composite.template create<AspectType>(static_cast<const Base&>(*this));
    ComposeData<CompositeType, GetData, Remainder...>::_addData(composite);
  }

  void _findData()
  {
    // Do nothing
  }

  template <typename Arg1, typename... Args>
  void _findData(const Arg1& arg1, const Args&... args)
  {
    _attemptToUse(static_cast<const typename ConvertIfData<Arg1>::Type&>(arg1));
    _findData(args...);
  }

  template <typename Arg>
  void _attemptToUse(const Arg&)
  {
    // Do nothing
  }

  void _attemptToUse(const typename Base::Data& data)
  {
    static_cast<Base&>(*this) = data;
  }

  void _attemptToUse(const CompositeType& composite)
  {
    _setBaseFrom(composite);
  }
};

//==============================================================================
template <typename... Aspects>
using MakeCompositeState = ComposeData<CompositeState, GetState, Aspects...>;

template <typename... Data>
using MakeCompositeProperties
    = ComposeData<CompositeProperties, GetProperties, Data...>;

} // namespace detail
} // namespace common
} // namespace dart

#endif // DART_COMMON_DETAIL_COMPOSITEDATA_HPP_
