/*=========================================================================
 *
 *  Copyright NumFOCUS
 *
 *  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
 *
 *         https://www.apache.org/licenses/LICENSE-2.0.txt
 *
 *  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 itkGPUDataManager_h
#define itkGPUDataManager_h

#include "itkObject.h"
#include "itkDataObject.h"
#include "itkObjectFactory.h"
#include "itkOpenCLUtil.h"
#include "itkGPUContextManager.h"
#include <mutex>

namespace itk
{
/** \class GPUDataManager
 * \brief GPU memory manager implemented using OpenCL. Required by GPUImage class.
 *
 * This class serves as a base class for GPU data container for GPUImage class,
 * which is similar to ImageBase class for Image class. However, all the image-related
 * meta data will be already stored in image class (parent of GPUImage), therefore
 * we did not name it GPUImageBase. Rather, this class is a GPU-specific data manager
 * that provides functionalities for CPU-GPU data synchronization and grafting GPU data.
 *
 * \ingroup ITKGPUCommon
 */
class GPUDataManager : public Object // DataObject//
{
  /** allow GPUKernelManager to access GPU buffer pointer */
  friend class GPUKernelManager;

public:
  ITK_DISALLOW_COPY_AND_MOVE(GPUDataManager);

  using Self = GPUDataManager;
  using Superclass = Object;
  using Pointer = SmartPointer<Self>;
  using ConstPointer = SmartPointer<const Self>;

  itkNewMacro(Self);
  itkOverrideGetNameOfClassMacro(GPUDataManager);

  using MutexHolderType = std::lock_guard<std::mutex>;

  /** total buffer size in bytes */
  void
  SetBufferSize(unsigned int num);

  unsigned int
  GetBufferSize() const
  {
    return m_BufferSize;
  }

  void
  SetBufferFlag(cl_mem_flags flags);

  void
  SetCPUBufferPointer(void * ptr);

  void
  SetCPUDirtyFlag(bool isDirty);

  void
  SetGPUDirtyFlag(bool isDirty);

  /** Make GPU up-to-date and mark CPU as dirty.
   * Call this function when you want to modify CPU data */
  void
  SetCPUBufferDirty();

  /** Make CPU up-to-date and mark GPU as dirty.
   * Call this function when you want to modify GPU data */
  void
  SetGPUBufferDirty();

  bool
  IsCPUBufferDirty() const
  {
    return m_IsCPUBufferDirty;
  }

  bool
  IsGPUBufferDirty() const
  {
    return m_IsGPUBufferDirty;
  }

  /** actual GPU->CPU memory copy takes place here */
  virtual void
  UpdateCPUBuffer();

  /** actual CPU->GPU memory copy takes place here */
  virtual void
  UpdateGPUBuffer();

  void
  Allocate();

  void
  SetCurrentCommandQueue(int queueid);

  int
  GetCurrentCommandQueueID() const;

  /** Synchronize CPU and GPU buffers (using dirty flags) */
  bool
  Update();

  /** Method for grafting the content of one GPUDataManager into another one */
  virtual void
  Graft(const GPUDataManager * data);

  /** Initialize GPUDataManager */
  virtual void
  Initialize();

  /** Get GPU buffer pointer */
  cl_mem *
  GetGPUBufferPointer();

  /** Get GPU buffer pointer */
  void *
  GetCPUBufferPointer();

protected:
  GPUDataManager();
  ~GPUDataManager() override;
  void
  PrintSelf(std::ostream & os, Indent indent) const override;

protected:
  /* NOTE: ivars are protected instead of private to improve performance access in child classes*/

  unsigned int m_BufferSize{}; // # of bytes

  GPUContextManager * m_ContextManager{};

  int m_CommandQueueId{};

  /** buffer type */
  cl_mem_flags m_MemFlags{};

  /** buffer pointers */
  cl_mem m_GPUBuffer{};
  void * m_CPUBuffer{};

  /** checks if buffer needs to be updated */
  bool m_IsGPUBufferDirty{};
  bool m_IsCPUBufferDirty{};

  /** Mutex lock to prevent r/w hazard for multithreaded code */
  std::mutex m_Mutex{};
};

} // namespace itk

#endif
