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#ifndef DART_DYNAMICS_NODE_HPP_
#define DART_DYNAMICS_NODE_HPP_

#include <memory>

#include "dart/common/Cloneable.hpp"
#include "dart/common/EmbeddedAspect.hpp"
#include "dart/common/Subject.hpp"
#include "dart/common/VersionCounter.hpp"

#include "dart/dynamics/SmartPointer.hpp"

namespace dart {
namespace dynamics {

class BodyNode;
class Node;

//==============================================================================
class NodeDestructor final
{
public:
  /// Constructor
  NodeDestructor(Node* _node);

  /// Do not copy
  NodeDestructor(const NodeDestructor& _other) = delete;

  /// Non-virtual destructor (this class cannot be inherited)
  ~NodeDestructor();

  Node* getNode() const;

private:
  /// Node that this Destructor is responsible for
  Node* mNode;
};

//==============================================================================
/// The Node class is a base class for BodyNode and any object that attaches to
/// a BodyNode. This base class handles ownership and reference counting for the
/// classes that inherit it.
///
/// In most cases, when creating your own custom Node class, you will also want
/// to inherit from AccessoryNode using CRTP.
class Node : public virtual common::Subject,
             public virtual common::VersionCounter
{
public:
  friend class BodyNode;
  friend class Skeleton;
  template <class>
  friend class AccessoryNode;
  template <class, class>
  friend class TemplateNodePtr;
  template <class, class>
  friend class TemplateWeakNodePtr;

  /// If your Node has a State class, then that State class should inherit this
  /// Node::State class. This allows us to safely serialize, store, and clone
  /// the states of arbitrary Node extensions. If your Node is stateless, then
  /// you do not have to worry about extending this class, because
  /// Node::getNodeState() will simply return a nullptr by default, which is
  /// taken to indicate that it is stateless.
  ///
  /// The distinction between the State class and the Properties class is that
  /// State will get stored in BodyNode::ExtendedState whereas Properties will
  /// get stored in BodyNode::ExtendedProperties. Typically Properties are
  /// values that only change rarely if ever, whereas State contains values that
  /// might change as often as every time step.
  class State : public common::Cloneable<State>
  {
  };

  /// Use the MakeState class to easily create a State extension from an
  /// existing class or struct
  template <class Mixin>
  using MakeState = common::MakeCloneable<State, Mixin>;

  /// If your Node has a Properties class, then that Properties class should
  /// inherit this Node::Properties class. This allows us to safely serialize,
  /// store, and clone the properties of arbitrary Node extensions. If your
  /// Node has no properties, then you do not have to worry about extending
  /// this class, because Node::getNodeProperties() will simply return a nullptr
  /// by default, which is taken to indicate that it has no properties.
  ///
  /// The distinction between the State class and the Properties class is that
  /// State will get stored in BodyNode::ExtendedState whereas Properties will
  /// get stored in BodyNode::ExtendedProperties. Typically Properties are
  /// values that only change rarely if ever, whereas State contains values that
  /// might change as often as every time step.
  class Properties : public common::Cloneable<Properties>
  {
  };

  /// Use the MakeProperties class to easily create a Properties extension
  /// from an existing class or struct.
  template <class Mixin>
  using MakeProperties = common::MakeCloneable<Properties, Mixin>;

  /// Virtual destructor
  virtual ~Node() = default;

  /// Set the name of this Node
  virtual const std::string& setName(const std::string& newName) = 0;

  /// Get the name of this Node
  virtual const std::string& getName() const = 0;

  /// Set the State of this Node. By default, this does nothing.
  virtual void setNodeState(const State& otherState);

  /// Get the State of this Node. By default, this returns a nullptr which
  /// implies that the Node is stateless.
  virtual std::unique_ptr<State> getNodeState() const;

  /// Copy the State of this Node into a unique_ptr. By default, this simply
  /// calls getNodeState() and passes the result into the outputState, but this
  /// function can be overriden to be more performant by avoiding allocations.
  virtual void copyNodeStateTo(std::unique_ptr<State>& outputState) const;

  /// Set the Properties of this Node. By default, this does nothing.
  virtual void setNodeProperties(const Properties& properties);

  /// Get the Properties of this Node. By default, this returns a nullptr which
  /// implies that the Node has no properties.
  virtual std::unique_ptr<Properties> getNodeProperties() const;

  /// Copy the Properties of this Node into a unique_ptr. By default, this
  /// simply calls getNodeProperties() and passes the result into the
  /// outputProperties, but this function can be overriden to be more
  /// performant.
  virtual void copyNodePropertiesTo(
      std::unique_ptr<Properties>& outputProperties) const;

  /// Get a pointer to the BodyNode that this Node is associated with
  BodyNodePtr getBodyNodePtr();

  /// Get a pointer to the BodyNode that this Node is associated with
  ConstBodyNodePtr getBodyNodePtr() const;

  /// Returns true if this Node has been staged for removal from its BodyNode.
  /// It will be deleted once all strong references to it expire. If it is an
  /// AccessoryNode, you can call reattach() to prevent that from happening.
  bool isRemoved() const;

  /// Return the Skeleton that this Node is attached to
  virtual std::shared_ptr<Skeleton> getSkeleton();

  /// Return the Skeleton that this Node is attached to
  virtual std::shared_ptr<const Skeleton> getSkeleton() const;

private:
  std::shared_ptr<NodeDestructor> getOrCreateDestructor();

protected:
  /// Allow your Node implementation to be cloned into a new BodyNode
  virtual Node* cloneNode(BodyNode* bn) const = 0;

  /// Constructor
  Node(BodyNode* _bn);

  /// Inform the Skeleton that the name of this Node has changed. If the name is
  /// already taken by another Node of the same type, then this function will
  /// return a modified version which is unique. If the name is not already
  /// taken, then it will just return the same name that the function was given.
  std::string registerNameChange(const std::string& newName);

  /// Attach the Node to its BodyNode
  void attach();

  /// When all external references to the Node disappear, it will be deleted
  void stageForRemoval();

  /// weak pointer to the destructor for this Node. We use a shared_ptr
  /// "destructor" class instead of managing Nodes directly with shared_ptrs
  /// because this scheme allows BodyNodes to circumvent the shared_ptr
  /// management by setting the mNode member of the Destructor to a nullptr.
  /// That way the BodyNode can never be deleted by its Destructor.
  std::weak_ptr<NodeDestructor> mDestructor;

  /// Pointer to the BodyNode that this Node is attached to
  BodyNode* mBodyNode;

  /// bool that tracks whether this Node is attached to its BodyNode
  bool mAmAttached;

  /// The index of this Node within its vector in its BodyNode's NodeMap
  std::size_t mIndexInBodyNode;

  /// The index of this Node within its vector in its Skeleton's NodeMap
  std::size_t mIndexInSkeleton;

  /// Index of this Node within its tree
  std::size_t mIndexInTree;
};

//==============================================================================
/// AccessoryNode provides an interface for Nodes to get their index within the
/// list of Nodes, as well as detach and reattach. This uses CRTP to get around
/// the diamond of death problem.
template <class NodeType>
class AccessoryNode
{
public:
  /// Virtual destructor
  virtual ~AccessoryNode() = default;

  /// Get the index of this Node within its BodyNode.
  std::size_t getIndexInBodyNode() const;

  /// Get the index of this Node within its Skeleton.
  std::size_t getIndexInSkeleton() const;

  /// Get the index of this Node within its tree.
  std::size_t getIndexInTree() const;

  /// Get the index of this Node's tree within its Skeleton
  std::size_t getTreeIndex() const;

  /// Stage the Node for removal. When all strong references to the Node expire,
  /// the Node will be removed from its BodyNode and deleted.
  void remove();

  /// Undo the effectos of calling remove(). The Node will continue to exist,
  /// even when all the strong references to it expire.
  void reattach();

protected:
  /// Prevent a non-inheriting class from constructing one
  AccessoryNode() = default;
};

} // namespace dynamics
} // namespace dart

#include "dart/dynamics/detail/Node.hpp"

#endif // DART_DYNAMICS_NODE_HPP_
