/***

  Olive - Non-Linear Video Editor
  Copyright (C) 2019 Olive Team

  This program is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program.  If not, see <http://www.gnu.org/licenses/>.

***/

#ifndef RENDERMANAGER_H
#define RENDERMANAGER_H

#include <QLinkedList>
#include <QOpenGLTexture>

#include "node/node.h"
#include "render/pixelformat.h"
#include "render/rendermodes.h"
#include "rendererdownloadthread.h"
#include "rendererprocessthread.h"

/**
 * @brief A multithreaded OpenGL based renderer for node systems
 */
class RenderManager : public QObject
{
  Q_OBJECT
public:
  /**
   * @brief Renderer Constructor
   *
   * Constructing a Renderer object will not start any threads/backend on its own. Use Start() to do this and Stop()
   * when the Renderer is about to be destroyed.
   */
  RenderManager();

  static void CreateInstance();

  static void DestroyInstance();

  static RenderManager* instance();

  void SetCacheName(const QString& s);

  void SetTimebase(const rational& timebase);

  void InvalidateCache(const rational &start_range, const rational &end_range, const rational &last_requested_time);

  /**
   * @brief Set parameters of the Renderer
   *
   * The Renderer owns the buffers that are used in the rendering process and this function sets the kind of buffers
   * to use. The Renderer must be stopped when calling this function.
   *
   * @param width
   *
   * Buffer width
   *
   * @param height
   *
   * Buffer height
   *
   * @param format
   *
   * Buffer pixel format
   */
  void SetParameters(const int& width,
                     const int& height,
                     const olive::PixelFormat& format,
                     const olive::RenderMode& mode,
                     NodeInput *input,
                     const int &divider = 0);

  void SetDivider(const int& divider);

  /**
   * @brief Return whether a frame with this hash already exists
   */
  bool HasHash(const QByteArray& hash);

  /**
   * @brief Return whether a frame is currently being cached
   */
  bool IsCaching(const QByteArray& hash);

  /**
   * @brief Check if a frame is currently being cached, and if not reserve it
   */
  bool TryCache(const QByteArray& hash);

  /**
   * @brief Retrieve the cached frame at `time` and upload it to `destination_texture`
   */
  void RetrieveImage(RenderTexturePtr destination_texture, const rational& time);

  /**
   * @brief Allocate and start the multithreaded backend
   */
  void Start();

  /**
   * @brief Terminate and deallocate the multithreaded backend
   */
  void Stop();

  /**
   * @brief Return current instance of a RenderThread (or nullptr if there is none)
   *
   * This function attempts a dynamic_cast on QThread::currentThread() to RendererThread, which will return nullptr if
   * the cast fails (e.g. if this function is called from the main thread rather than a RendererThread).
   */
  static RendererThreadBase* CurrentThread();

  static RenderInstance* CurrentInstance();

signals:
  void FrameReady(rational time);

  void FrameReadyWithTexture(rational time, RenderTexturePtr texture);

private:
  static RenderManager* instance_;

  struct HashTimeMapping {
    rational time;
    QByteArray hash;
  };

  /**
   * @brief Internal function for generating the cache ID
   */
  void GenerateCacheIDInternal();

  /**
   * @brief Function called when there are frames in the queue to cache
   *
   * This function is NOT thread-safe and should only be called in the main thread.
   */
  void CacheNext();

  bool ShouldPushTexture(const rational &time);

  /**
   * @brief Return the path of the cached image at this time
   */
  QString CachePathName(const QByteArray &hash);

  void DeferMap(const rational &time, const QByteArray &hash);

  /**
   * @brief Internal list of RenderProcessThreads
   */
  QVector<RendererProcessThreadPtr> threads_;

  /**
   * @brief Internal variable that contains whether the Renderer has started or not
   */
  bool started_;

  int width_;
  int height_;

  void CalculateEffectiveDimensions();

  int divider_;
  int effective_width_;
  int effective_height_;

  olive::PixelFormat format_;

  olive::RenderMode mode_;

  rational timebase_;
  double timebase_dbl_;

  QLinkedList<rational> cache_queue_;
  QString cache_name_;
  qint64 cache_time_;
  QString cache_id_;

  bool caching_;
  QVector<uchar*> cache_frame_load_buffer_;

  QVector<RendererDownloadThreadPtr> download_threads_;
  int last_download_thread_;

  QMap<rational, QByteArray> time_hash_map_;

  QMutex cache_hash_list_mutex_;
  QVector<QByteArray> cache_hash_list_;

  QList<HashTimeMapping> deferred_maps_;

  NodeInput* texture_input_;

private slots:
  void ThreadCallback(RenderTexturePtr texture, const rational& time, const QByteArray& hash);

  void ThreadRequestSibling(NodeDependency dep);

  void ThreadSkippedFrame(const rational &time, const QByteArray &hash);

  void DownloadThreadComplete(const QByteArray &hash);

};

#endif // RENDERMANAGER_H