/*
 * Copyright 2011-2021 Blender Foundation
 *
 * 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
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * 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.
 */

#pragma once

#include "integrator/pass_accessor.h"
#include "scene/pass.h"
#include "session/buffers.h"
#include "util/types.h"
#include "util/unique_ptr.h"

CCL_NAMESPACE_BEGIN

class BufferParams;
class Device;
class DeviceScene;
class Film;
class PathTraceDisplay;
class RenderBuffers;

class PathTraceWork {
 public:
  struct RenderStatistics {
    float occupancy = 1.0f;
  };

  /* Create path trace work which fits best the device.
   *
   * The cancel request flag is used for a cheap check whether cancel is to be performed as soon as
   * possible. This could be, for example, request to cancel rendering on camera navigation in
   * viewport. */
  static unique_ptr<PathTraceWork> create(Device *device,
                                          Film *film,
                                          DeviceScene *device_scene,
                                          bool *cancel_requested_flag);

  virtual ~PathTraceWork();

  /* Access the render buffers.
   *
   * Is only supposed to be used by the PathTrace to update buffer allocation and slicing to
   * correspond to the big tile size and relative device performance. */
  RenderBuffers *get_render_buffers();

  /* Set effective parameters of the big tile and the work itself. */
  void set_effective_buffer_params(const BufferParams &effective_full_params,
                                   const BufferParams &effective_big_tile_params,
                                   const BufferParams &effective_buffer_params);

  /* Check whether the big tile is being worked on by multiple path trace works. */
  bool has_multiple_works() const;

  /* Allocate working memory for execution. Must be called before init_execution(). */
  virtual void alloc_work_memory(){};

  /* Initialize execution of kernels.
   * Will ensure that all device queues are initialized for execution.
   *
   * This method is to be called after any change in the scene. It is not needed to call it prior
   * to an every call of the `render_samples()`. */
  virtual void init_execution() = 0;

  /* Render given number of samples as a synchronous blocking call.
   * The samples are added to the render buffer associated with this work. */
  virtual void render_samples(RenderStatistics &statistics,
                              int start_sample,
                              int samples_num,
                              int sample_offset) = 0;

  /* Copy render result from this work to the corresponding place of the GPU display.
   *
   * The `pass_mode` indicates whether to access denoised or noisy version of the display pass. The
   * noisy pass mode will be passed here when it is known that the buffer does not have denoised
   * passes yet (because denoiser did not run). If the denoised pass is requested and denoiser is
   * not used then this function will fall-back to the noisy pass instead. */
  virtual void copy_to_display(PathTraceDisplay *display, PassMode pass_mode, int num_samples) = 0;

  virtual void destroy_gpu_resources(PathTraceDisplay *display) = 0;

  /* Copy data from/to given render buffers.
   * Will copy pixels from a corresponding place (from multi-device point of view) of the render
   * buffers, and copy work's render buffers to the corresponding place of the destination. */

  /* Notes:
   * - Copies work's render buffer from the device.
   * - Copies CPU-side buffer of the given buffer
   * - Does not copy the buffer to its device. */
  void copy_to_render_buffers(RenderBuffers *render_buffers);

  /* Notes:
   * - Does not copy given render buffers from the device.
   * - Copies work's render buffer to its device. */
  void copy_from_render_buffers(const RenderBuffers *render_buffers);

  /* Special version of the `copy_from_render_buffers()` which only copies denoised passes from the
   * given render buffers, leaving rest of the passes.
   *
   * Same notes about device copying applies to this call as well. */
  void copy_from_denoised_render_buffers(const RenderBuffers *render_buffers);

  /* Copy render buffers to/from device using an appropriate device queue when needed so that
   * things are executed in order with the `render_samples()`. */
  virtual bool copy_render_buffers_from_device() = 0;
  virtual bool copy_render_buffers_to_device() = 0;

  /* Zero render buffers to/from device using an appropriate device queue when needed so that
   * things are executed in order with the `render_samples()`. */
  virtual bool zero_render_buffers() = 0;

  /* Access pixels rendered by this work and copy them to the corresponding location in the
   * destination.
   *
   * NOTE: Does not perform copy of buffers from the device. Use `copy_render_tile_from_device()`
   * to update host-side data. */
  bool get_render_tile_pixels(const PassAccessor &pass_accessor,
                              const PassAccessor::Destination &destination);

  /* Set pass data for baking. */
  bool set_render_tile_pixels(PassAccessor &pass_accessor, const PassAccessor::Source &source);

  /* Perform convergence test on the render buffer, and filter the convergence mask.
   * Returns number of active pixels (the ones which did not converge yet). */
  virtual int adaptive_sampling_converge_filter_count_active(float threshold, bool reset) = 0;

  /* Run cryptomatte pass post-processing kernels. */
  virtual void cryptomatte_postproces() = 0;

  /* Cheap-ish request to see whether rendering is requested and is to be stopped as soon as
   * possible, without waiting for any samples to be finished. */
  inline bool is_cancel_requested() const
  {
    /* NOTE: Rely on the fact that on x86 CPU reading scalar can happen without atomic even in
     * threaded environment. */
    return *cancel_requested_flag_;
  }

  /* Access to the device which is used to path trace this work on. */
  Device *get_device() const
  {
    return device_;
  }

 protected:
  PathTraceWork(Device *device,
                Film *film,
                DeviceScene *device_scene,
                bool *cancel_requested_flag);

  PassAccessor::PassAccessInfo get_display_pass_access_info(PassMode pass_mode) const;

  /* Get destination which offset and stride are configured so that writing to it will write to a
   * proper location of GPU display texture, taking current tile and device slice into account. */
  PassAccessor::Destination get_display_destination_template(
      const PathTraceDisplay *display) const;

  /* Device which will be used for path tracing.
   * Note that it is an actual render device (and never is a multi-device). */
  Device *device_;

  /* Film is used to access display pass configuration for GPU display update.
   * Note that only fields which are not a part of kernel data can be accessed via the Film. */
  Film *film_;

  /* Device side scene storage, that may be used for integrator logic. */
  DeviceScene *device_scene_;

  /* Render buffers where sampling is being accumulated into, allocated for a fraction of the big
   * tile which is being rendered by this work.
   * It also defines possible subset of a big tile in the case of multi-device rendering. */
  unique_ptr<RenderBuffers> buffers_;

  /* Effective parameters of the full, big tile, and current work render buffer.
   * The latter might be different from `buffers_->params` when there is a resolution divider
   * involved. */
  BufferParams effective_full_params_;
  BufferParams effective_big_tile_params_;
  BufferParams effective_buffer_params_;

  bool *cancel_requested_flag_ = nullptr;
};

CCL_NAMESPACE_END
