/* SPDX-License-Identifier: GPL-2.0-or-later
 * Copyright 2021 Blender Foundation.
 */

/** \file
 * \ingroup eevee
 *
 * An instance contains all structures needed to do a complete render.
 */

#include <sstream>

#include "BKE_global.h"
#include "BKE_object.h"
#include "BLI_rect.h"
#include "DEG_depsgraph_query.h"
#include "DNA_ID.h"
#include "DNA_lightprobe_types.h"
#include "DNA_modifier_types.h"
#include "RE_pipeline.h"

#include "eevee_instance.hh"

namespace blender::eevee {

/* -------------------------------------------------------------------- */
/** \name Initialization
 *
 * Initialization functions need to be called once at the start of a frame.
 * Active camera, render extent and enabled render passes are immutable until next init.
 * This takes care of resizing output buffers and view in case a parameter changed.
 * IMPORTANT: xxx.init() functions are NOT meant to acquire and allocate DRW resources.
 * Any attempt to do so will likely produce use after free situations.
 * \{ */

void Instance::init(const int2 &output_res,
                    const rcti *output_rect,
                    RenderEngine *render_,
                    Depsgraph *depsgraph_,
                    const LightProbe *light_probe_,
                    Object *camera_object_,
                    const RenderLayer *render_layer_,
                    const DRWView *drw_view_,
                    const View3D *v3d_,
                    const RegionView3D *rv3d_)
{
  UNUSED_VARS(light_probe_);
  render = render_;
  depsgraph = depsgraph_;
  camera_orig_object = camera_object_;
  render_layer = render_layer_;
  drw_view = drw_view_;
  v3d = v3d_;
  rv3d = rv3d_;

  info = "";

  update_eval_members();

  sampling.init(scene);
  camera.init();
  film.init(output_res, output_rect);
  main_view.init();
}

void Instance::set_time(float time)
{
  BLI_assert(render);
  DRW_render_set_time(render, depsgraph, floorf(time), fractf(time));
  update_eval_members();
}

void Instance::update_eval_members()
{
  scene = DEG_get_evaluated_scene(depsgraph);
  view_layer = DEG_get_evaluated_view_layer(depsgraph);
  camera_eval_object = (camera_orig_object) ?
                           DEG_get_evaluated_object(depsgraph, camera_orig_object) :
                           nullptr;
}

/** \} */

/* -------------------------------------------------------------------- */
/** \name Sync
 *
 * Sync will gather data from the scene that can change over a time step (i.e: motion steps).
 * IMPORTANT: xxx.sync() functions area responsible for creating DRW resources (i.e: DRWView) as
 * well as querying temp texture pool. All DRWPasses should be ready by the end end_sync().
 * \{ */

void Instance::begin_sync()
{
  materials.begin_sync();
  velocity.begin_sync();

  gpencil_engine_enabled = false;

  render_buffers.sync();
  pipelines.sync();
  main_view.sync();
  world.sync();
  camera.sync();
  film.sync();
}

void Instance::object_sync(Object *ob)
{
  const bool is_renderable_type = ELEM(ob->type, OB_CURVES, OB_GPENCIL, OB_MESH);
  const int ob_visibility = DRW_object_visibility_in_active_context(ob);
  const bool partsys_is_visible = (ob_visibility & OB_VISIBLE_PARTICLES) != 0 &&
                                  (ob->type == OB_MESH);
  const bool object_is_visible = DRW_object_is_renderable(ob) &&
                                 (ob_visibility & OB_VISIBLE_SELF) != 0;

  if (!is_renderable_type || (!partsys_is_visible && !object_is_visible)) {
    return;
  }

  ObjectHandle &ob_handle = sync.sync_object(ob);

  if (partsys_is_visible && ob != DRW_context_state_get()->object_edit) {
    LISTBASE_FOREACH (ModifierData *, md, &ob->modifiers) {
      if (md->type == eModifierType_ParticleSystem) {
        sync.sync_curves(ob, ob_handle, md);
      }
    }
  }

  if (object_is_visible) {
    switch (ob->type) {
      case OB_LAMP:
        break;
      case OB_MESH:
      case OB_CURVES_LEGACY:
      case OB_SURF:
      case OB_FONT:
      case OB_MBALL: {
        sync.sync_mesh(ob, ob_handle);
        break;
      }
      case OB_VOLUME:
        break;
      case OB_CURVES:
        sync.sync_curves(ob, ob_handle);
        break;
      case OB_GPENCIL:
        sync.sync_gpencil(ob, ob_handle);
        break;
      default:
        break;
    }
  }

  ob_handle.reset_recalc_flag();
}

/* Wrapper to use with DRW_render_object_iter. */
void Instance::object_sync_render(void *instance_,
                                  Object *ob,
                                  RenderEngine *engine,
                                  Depsgraph *depsgraph)
{
  UNUSED_VARS(engine, depsgraph);
  Instance &inst = *reinterpret_cast<Instance *>(instance_);
  inst.object_sync(ob);
}

void Instance::end_sync()
{
  velocity.end_sync();
  sampling.end_sync();
  film.end_sync();
}

void Instance::render_sync()
{
  DRW_cache_restart();

  begin_sync();
  DRW_render_object_iter(this, render, depsgraph, object_sync_render);
  end_sync();

  DRW_render_instance_buffer_finish();
  /* Also we weed to have a correct FBO bound for #DRW_hair_update */
  // GPU_framebuffer_bind();
  // DRW_hair_update();
}

/** \} */

/* -------------------------------------------------------------------- */
/** \name Rendering
 * \{ */

/**
 * Conceptually renders one sample per pixel.
 * Everything based on random sampling should be done here (i.e: DRWViews jitter)
 **/
void Instance::render_sample()
{
  if (sampling.finished_viewport()) {
    film.display();
    return;
  }

  /* Motion blur may need to do re-sync after a certain number of sample. */
  if (!is_viewport() && sampling.do_render_sync()) {
    render_sync();
  }

  sampling.step();

  main_view.render();
}

/** \} */

/* -------------------------------------------------------------------- */
/** \name Interface
 * \{ */

void Instance::render_frame(RenderLayer *render_layer, const char *view_name)
{
  while (!sampling.finished()) {
    this->render_sample();
    /* TODO(fclem) print progression. */
  }

  /* Read Results. */
  eViewLayerEEVEEPassType pass_bits = film.enabled_passes_get();
  for (auto i : IndexRange(EEVEE_RENDER_PASS_MAX_BIT)) {
    eViewLayerEEVEEPassType pass_type = eViewLayerEEVEEPassType(pass_bits & (1 << i));
    if (pass_type == 0) {
      continue;
    }

    const char *pass_name = Film::pass_to_render_pass_name(pass_type);
    RenderPass *rp = RE_pass_find_by_name(render_layer, pass_name, view_name);
    if (rp) {
      float *result = film.read_pass(pass_type);
      if (result) {
        std::cout << "read " << pass_name << std::endl;
        BLI_mutex_lock(&render->update_render_passes_mutex);
        /* WORKAROUND: We use texture read to avoid using a framebuffer to get the render result.
         * However, on some implementation, we need a buffer with a few extra bytes for the read to
         * happen correctly (see GLTexture::read()). So we need a custom memory allocation. */
        /* Avoid memcpy(), replace the pointer directly. */
        MEM_SAFE_FREE(rp->rect);
        rp->rect = result;
        BLI_mutex_unlock(&render->update_render_passes_mutex);
      }
    }
  }
}

void Instance::draw_viewport(DefaultFramebufferList *dfbl)
{
  UNUSED_VARS(dfbl);
  render_sample();
  velocity.step_swap();

  if (!sampling.finished_viewport()) {
    DRW_viewport_request_redraw();
  }

  if (materials.queued_shaders_count > 0) {
    std::stringstream ss;
    ss << "Compiling Shaders " << materials.queued_shaders_count;
    info = ss.str();
  }
}

/** \} */

}  // namespace blender::eevee