//----------------------------------------------------------------------------//
//                                                                            //
// ozz-animation is hosted at http://github.com/guillaumeblanc/ozz-animation  //
// and distributed under the MIT License (MIT).                               //
//                                                                            //
// Copyright (c) Guillaume Blanc                                              //
//                                                                            //
// Permission is hereby granted, free of charge, to any person obtaining a    //
// copy of this software and associated documentation files (the "Software"), //
// to deal in the Software without restriction, including without limitation  //
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// and/or sell copies of the Software, and to permit persons to whom the      //
// Software is furnished to do so, subject to the following conditions:       //
//                                                                            //
// The above copyright notice and this permission notice shall be included in //
// all copies or substantial portions of the Software.                        //
//                                                                            //
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,   //
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// DEALINGS IN THE SOFTWARE.                                                  //
//                                                                            //
//----------------------------------------------------------------------------//

#ifndef OZZ_OZZ_ANIMATION_RUNTIME_SKELETON_H_
#define OZZ_OZZ_ANIMATION_RUNTIME_SKELETON_H_

#include "ozz/base/io/archive_traits.h"
#include "ozz/base/platform.h"
#include "ozz/base/span.h"

namespace ozz {
namespace io {
class IArchive;
class OArchive;
}  // namespace io
namespace math {
struct SoaTransform;
}
namespace animation {

// Forward declaration of SkeletonBuilder, used to instantiate a skeleton.
namespace offline {
class SkeletonBuilder;
}

// This runtime skeleton data structure provides a const-only access to joint
// hierarchy, joint names and bind-pose. This structure is filled by the
// SkeletonBuilder and can be serialize/deserialized.
// Joint names, bind-poses and hierarchy information are all stored in separate
// arrays of data (as opposed to joint structures for the RawSkeleton), in order
// to closely match with the way runtime algorithms use them. Joint hierarchy is
// packed as an array of parent jont indices (16 bits), stored in depth-first
// order. This is enough to traverse the whole joint hierarchy. See
// IterateJointsDF() from skeleton_utils.h that implements a depth-first
// traversal utility.
class Skeleton {
 public:
  // Defines Skeleton constant values.
  enum Constants {

    // Defines the maximum number of joints.
    // This is limited in order to control the number of bits required to store
    // a joint index. Limiting the number of joints also helps handling worst
    // size cases, like when it is required to allocate an array of joints on
    // the stack.
    kMaxJoints = 1024,

    // Defines the maximum number of SoA elements required to store the maximum
    // number of joints.
    kMaxSoAJoints = (kMaxJoints + 3) / 4,

    // Defines the index of the parent of the root joint (which has no parent in
    // fact).
    kNoParent = -1,
  };

  // Builds a default skeleton.
  Skeleton();

  // Declares the public non-virtual destructor.
  ~Skeleton();

  // Returns the number of joints of *this skeleton.
  int num_joints() const { return static_cast<int>(joint_parents_.size()); }

  // Returns the number of soa elements matching the number of joints of *this
  // skeleton. This value is useful to allocate SoA runtime data structures.
  int num_soa_joints() const { return (num_joints() + 3) / 4; }

  // Returns joint's bind poses. Bind poses are stored in soa format.
  span<const math::SoaTransform> joint_bind_poses() const {
    return joint_bind_poses_;
  }

  // Returns joint's parent indices range.
  span<const int16_t> joint_parents() const { return joint_parents_; }

  // Returns joint's name collection.
  span<const char* const> joint_names() const {
    return span<const char* const>(joint_names_.begin(), joint_names_.end());
  }

  // Serialization functions.
  // Should not be called directly but through io::Archive << and >> operators.
  void Save(ozz::io::OArchive& _archive) const;
  void Load(ozz::io::IArchive& _archive, uint32_t _version);

 private:
  // Disables copy and assignation.
  Skeleton(Skeleton const&);
  void operator=(Skeleton const&);

  // Internal allocation/deallocation function.
  // Allocate returns the beginning of the contiguous buffer of names.
  char* Allocate(size_t _char_count, size_t _num_joints);
  void Deallocate();

  // SkeletonBuilder class is allowed to instantiate an Skeleton.
  friend class offline::SkeletonBuilder;

  // Buffers below store joint informations in joing depth first order. Their
  // size is equal to the number of joints of the skeleton.

  // Bind pose of every joint in local space.
  span<math::SoaTransform> joint_bind_poses_;

  // Array of joint parent indexes.
  span<int16_t> joint_parents_;

  // Stores the name of every joint in an array of c-strings.
  span<char*> joint_names_;
};
}  // namespace animation

namespace io {
OZZ_IO_TYPE_VERSION(2, animation::Skeleton)
OZZ_IO_TYPE_TAG("ozz-skeleton", animation::Skeleton)
}  // namespace io
}  // namespace ozz
#endif  // OZZ_OZZ_ANIMATION_RUNTIME_SKELETON_H_