/* SPDX-License-Identifier: Apache-2.0
 * Copyright 2011-2022 Blender Foundation */

#pragma once

#include "kernel/film/adaptive_sampling.h"
#include "kernel/film/write_passes.h"

#include "kernel/integrator/shadow_catcher.h"

CCL_NAMESPACE_BEGIN

/* --------------------------------------------------------------------
 * BSDF Evaluation
 *
 * BSDF evaluation result, split between diffuse and glossy. This is used to
 * accumulate render passes separately. Note that reflection, transmission
 * and volume scattering are written to different render passes, but we assume
 * that only one of those can happen at a bounce, and so do not need to accumulate
 * them separately. */

ccl_device_inline void bsdf_eval_init(ccl_private BsdfEval *eval,
                                      const ClosureType closure_type,
                                      float3 value)
{
  eval->diffuse = zero_float3();
  eval->glossy = zero_float3();

  if (CLOSURE_IS_BSDF_DIFFUSE(closure_type)) {
    eval->diffuse = value;
  }
  else if (CLOSURE_IS_BSDF_GLOSSY(closure_type)) {
    eval->glossy = value;
  }

  eval->sum = value;
}

ccl_device_inline void bsdf_eval_accum(ccl_private BsdfEval *eval,
                                       const ClosureType closure_type,
                                       float3 value)
{
  if (CLOSURE_IS_BSDF_DIFFUSE(closure_type)) {
    eval->diffuse += value;
  }
  else if (CLOSURE_IS_BSDF_GLOSSY(closure_type)) {
    eval->glossy += value;
  }

  eval->sum += value;
}

ccl_device_inline bool bsdf_eval_is_zero(ccl_private BsdfEval *eval)
{
  return is_zero(eval->sum);
}

ccl_device_inline void bsdf_eval_mul(ccl_private BsdfEval *eval, float value)
{
  eval->diffuse *= value;
  eval->glossy *= value;
  eval->sum *= value;
}

ccl_device_inline void bsdf_eval_mul(ccl_private BsdfEval *eval, float3 value)
{
  eval->diffuse *= value;
  eval->glossy *= value;
  eval->sum *= value;
}

ccl_device_inline float3 bsdf_eval_sum(ccl_private const BsdfEval *eval)
{
  return eval->sum;
}

ccl_device_inline float3 bsdf_eval_pass_diffuse_weight(ccl_private const BsdfEval *eval)
{
  /* Ratio of diffuse weight to recover proportions for writing to render pass.
   * We assume reflection, transmission and volume scatter to be exclusive. */
  return safe_divide(eval->diffuse, eval->sum);
}

ccl_device_inline float3 bsdf_eval_pass_glossy_weight(ccl_private const BsdfEval *eval)
{
  /* Ratio of glossy weight to recover proportions for writing to render pass.
   * We assume reflection, transmission and volume scatter to be exclusive. */
  return safe_divide(eval->glossy, eval->sum);
}

/* --------------------------------------------------------------------
 * Clamping
 *
 * Clamping is done on a per-contribution basis so that we can write directly
 * to render buffers instead of using per-thread memory, and to avoid the
 * impact of clamping on other contributions. */

ccl_device_forceinline void kernel_accum_clamp(KernelGlobals kg, ccl_private float3 *L, int bounce)
{
#ifdef __KERNEL_DEBUG_NAN__
  if (!isfinite_safe(*L)) {
    kernel_assert(!"Cycles sample with non-finite value detected");
  }
#endif
  /* Make sure all components are finite, allowing the contribution to be usable by adaptive
   * sampling convergence check, but also to make it so render result never causes issues with
   * post-processing. */
  *L = ensure_finite(*L);

#ifdef __CLAMP_SAMPLE__
  float limit = (bounce > 0) ? kernel_data.integrator.sample_clamp_indirect :
                               kernel_data.integrator.sample_clamp_direct;
  float sum = reduce_add(fabs(*L));
  if (sum > limit) {
    *L *= limit / sum;
  }
#endif
}

/* --------------------------------------------------------------------
 * Pass accumulation utilities.
 */

/* Get pointer to pixel in render buffer. */
ccl_device_forceinline ccl_global float *kernel_accum_pixel_render_buffer(
    KernelGlobals kg, ConstIntegratorState state, ccl_global float *ccl_restrict render_buffer)
{
  const uint32_t render_pixel_index = INTEGRATOR_STATE(state, path, render_pixel_index);
  const uint64_t render_buffer_offset = (uint64_t)render_pixel_index *
                                        kernel_data.film.pass_stride;
  return render_buffer + render_buffer_offset;
}

/* --------------------------------------------------------------------
 * Adaptive sampling.
 */

ccl_device_inline int kernel_accum_sample(KernelGlobals kg,
                                          ConstIntegratorState state,
                                          ccl_global float *ccl_restrict render_buffer,
                                          int sample,
                                          int sample_offset)
{
  if (kernel_data.film.pass_sample_count == PASS_UNUSED) {
    return sample;
  }

  ccl_global float *buffer = kernel_accum_pixel_render_buffer(kg, state, render_buffer);

  return atomic_fetch_and_add_uint32(
             (ccl_global uint *)(buffer) + kernel_data.film.pass_sample_count, 1) +
         sample_offset;
}

ccl_device void kernel_accum_adaptive_buffer(KernelGlobals kg,
                                             const int sample,
                                             const float3 contribution,
                                             ccl_global float *ccl_restrict buffer)
{
  /* Adaptive Sampling. Fill the additional buffer with the odd samples and calculate our stopping
   * criteria. This is the heuristic from "A hierarchical automatic stopping condition for Monte
   * Carlo global illumination" except that here it is applied per pixel and not in hierarchical
   * tiles. */

  if (kernel_data.film.pass_adaptive_aux_buffer == PASS_UNUSED) {
    return;
  }

  if (sample_is_even(kernel_data.integrator.sampling_pattern, sample)) {
    kernel_write_pass_float4(
        buffer + kernel_data.film.pass_adaptive_aux_buffer,
        make_float4(contribution.x * 2.0f, contribution.y * 2.0f, contribution.z * 2.0f, 0.0f));
  }
}

/* --------------------------------------------------------------------
 * Shadow catcher.
 */

#ifdef __SHADOW_CATCHER__

/* Accumulate contribution to the Shadow Catcher pass.
 *
 * Returns truth if the contribution is fully handled here and is not to be added to the other
 * passes (like combined, adaptive sampling). */

ccl_device bool kernel_accum_shadow_catcher(KernelGlobals kg,
                                            const uint32_t path_flag,
                                            const float3 contribution,
                                            ccl_global float *ccl_restrict buffer)
{
  if (!kernel_data.integrator.has_shadow_catcher) {
    return false;
  }

  kernel_assert(kernel_data.film.pass_shadow_catcher != PASS_UNUSED);
  kernel_assert(kernel_data.film.pass_shadow_catcher_matte != PASS_UNUSED);

  /* Matte pass. */
  if (kernel_shadow_catcher_is_matte_path(path_flag)) {
    kernel_write_pass_float3(buffer + kernel_data.film.pass_shadow_catcher_matte, contribution);
    /* NOTE: Accumulate the combined pass and to the samples count pass, so that the adaptive
     * sampling is based on how noisy the combined pass is as if there were no catchers in the
     * scene. */
  }

  /* Shadow catcher pass. */
  if (kernel_shadow_catcher_is_object_pass(path_flag)) {
    kernel_write_pass_float3(buffer + kernel_data.film.pass_shadow_catcher, contribution);
    return true;
  }

  return false;
}

ccl_device bool kernel_accum_shadow_catcher_transparent(KernelGlobals kg,
                                                        const uint32_t path_flag,
                                                        const float3 contribution,
                                                        const float transparent,
                                                        ccl_global float *ccl_restrict buffer)
{
  if (!kernel_data.integrator.has_shadow_catcher) {
    return false;
  }

  kernel_assert(kernel_data.film.pass_shadow_catcher != PASS_UNUSED);
  kernel_assert(kernel_data.film.pass_shadow_catcher_matte != PASS_UNUSED);

  if (path_flag & PATH_RAY_SHADOW_CATCHER_BACKGROUND) {
    return true;
  }

  /* Matte pass. */
  if (kernel_shadow_catcher_is_matte_path(path_flag)) {
    kernel_write_pass_float4(
        buffer + kernel_data.film.pass_shadow_catcher_matte,
        make_float4(contribution.x, contribution.y, contribution.z, transparent));
    /* NOTE: Accumulate the combined pass and to the samples count pass, so that the adaptive
     * sampling is based on how noisy the combined pass is as if there were no catchers in the
     * scene. */
  }

  /* Shadow catcher pass. */
  if (kernel_shadow_catcher_is_object_pass(path_flag)) {
    /* NOTE: The transparency of the shadow catcher pass is ignored. It is not needed for the
     * calculation and the alpha channel of the pass contains numbers of samples contributed to a
     * pixel of the pass. */
    kernel_write_pass_float3(buffer + kernel_data.film.pass_shadow_catcher, contribution);
    return true;
  }

  return false;
}

ccl_device void kernel_accum_shadow_catcher_transparent_only(KernelGlobals kg,
                                                             const uint32_t path_flag,
                                                             const float transparent,
                                                             ccl_global float *ccl_restrict buffer)
{
  if (!kernel_data.integrator.has_shadow_catcher) {
    return;
  }

  kernel_assert(kernel_data.film.pass_shadow_catcher_matte != PASS_UNUSED);

  /* Matte pass. */
  if (kernel_shadow_catcher_is_matte_path(path_flag)) {
    kernel_write_pass_float(buffer + kernel_data.film.pass_shadow_catcher_matte + 3, transparent);
  }
}

#endif /* __SHADOW_CATCHER__ */

/* --------------------------------------------------------------------
 * Render passes.
 */

/* Write combined pass. */
ccl_device_inline void kernel_accum_combined_pass(KernelGlobals kg,
                                                  const uint32_t path_flag,
                                                  const int sample,
                                                  const float3 contribution,
                                                  ccl_global float *ccl_restrict buffer)
{
#ifdef __SHADOW_CATCHER__
  if (kernel_accum_shadow_catcher(kg, path_flag, contribution, buffer)) {
    return;
  }
#endif

  if (kernel_data.film.light_pass_flag & PASSMASK(COMBINED)) {
    kernel_write_pass_float3(buffer + kernel_data.film.pass_combined, contribution);
  }

  kernel_accum_adaptive_buffer(kg, sample, contribution, buffer);
}

/* Write combined pass with transparency. */
ccl_device_inline void kernel_accum_combined_transparent_pass(KernelGlobals kg,
                                                              const uint32_t path_flag,
                                                              const int sample,
                                                              const float3 contribution,
                                                              const float transparent,
                                                              ccl_global float *ccl_restrict
                                                                  buffer)
{
#ifdef __SHADOW_CATCHER__
  if (kernel_accum_shadow_catcher_transparent(kg, path_flag, contribution, transparent, buffer)) {
    return;
  }
#endif

  if (kernel_data.film.light_pass_flag & PASSMASK(COMBINED)) {
    kernel_write_pass_float4(
        buffer + kernel_data.film.pass_combined,
        make_float4(contribution.x, contribution.y, contribution.z, transparent));
  }

  kernel_accum_adaptive_buffer(kg, sample, contribution, buffer);
}

/* Write background or emission to appropriate pass. */
ccl_device_inline void kernel_accum_emission_or_background_pass(
    KernelGlobals kg,
    ConstIntegratorState state,
    float3 contribution,
    ccl_global float *ccl_restrict buffer,
    const int pass,
    const int lightgroup = LIGHTGROUP_NONE)
{
  if (!(kernel_data.film.light_pass_flag & PASS_ANY)) {
    return;
  }

#ifdef __PASSES__
  const uint32_t path_flag = INTEGRATOR_STATE(state, path, flag);
  int pass_offset = PASS_UNUSED;

  /* Denoising albedo. */
#  ifdef __DENOISING_FEATURES__
  if (path_flag & PATH_RAY_DENOISING_FEATURES) {
    if (kernel_data.film.pass_denoising_albedo != PASS_UNUSED) {
      const float3 denoising_feature_throughput = INTEGRATOR_STATE(
          state, path, denoising_feature_throughput);
      const float3 denoising_albedo = denoising_feature_throughput * contribution;
      kernel_write_pass_float3(buffer + kernel_data.film.pass_denoising_albedo, denoising_albedo);
    }
  }
#  endif /* __DENOISING_FEATURES__ */

  if (lightgroup != LIGHTGROUP_NONE && kernel_data.film.pass_lightgroup != PASS_UNUSED) {
    kernel_write_pass_float3(buffer + kernel_data.film.pass_lightgroup + 3 * lightgroup,
                             contribution);
  }

  if (!(path_flag & PATH_RAY_ANY_PASS)) {
    /* Directly visible, write to emission or background pass. */
    pass_offset = pass;
  }
  else if (kernel_data.kernel_features & KERNEL_FEATURE_LIGHT_PASSES) {
    /* Don't write any light passes for shadow catcher, for easier
     * compositing back together of the combined pass. */
    if (path_flag & PATH_RAY_SHADOW_CATCHER_HIT) {
      return;
    }

    if (path_flag & PATH_RAY_SURFACE_PASS) {
      /* Indirectly visible through reflection. */
      const float3 diffuse_weight = INTEGRATOR_STATE(state, path, pass_diffuse_weight);
      const float3 glossy_weight = INTEGRATOR_STATE(state, path, pass_glossy_weight);

      /* Glossy */
      const int glossy_pass_offset = ((INTEGRATOR_STATE(state, path, bounce) == 1) ?
                                          kernel_data.film.pass_glossy_direct :
                                          kernel_data.film.pass_glossy_indirect);
      if (glossy_pass_offset != PASS_UNUSED) {
        kernel_write_pass_float3(buffer + glossy_pass_offset, glossy_weight * contribution);
      }

      /* Transmission */
      const int transmission_pass_offset = ((INTEGRATOR_STATE(state, path, bounce) == 1) ?
                                                kernel_data.film.pass_transmission_direct :
                                                kernel_data.film.pass_transmission_indirect);

      if (transmission_pass_offset != PASS_UNUSED) {
        /* Transmission is what remains if not diffuse and glossy, not stored explicitly to save
         * GPU memory. */
        const float3 transmission_weight = one_float3() - diffuse_weight - glossy_weight;
        kernel_write_pass_float3(buffer + transmission_pass_offset,
                                 transmission_weight * contribution);
      }

      /* Reconstruct diffuse subset of throughput. */
      pass_offset = (INTEGRATOR_STATE(state, path, bounce) == 1) ?
                        kernel_data.film.pass_diffuse_direct :
                        kernel_data.film.pass_diffuse_indirect;
      if (pass_offset != PASS_UNUSED) {
        contribution *= diffuse_weight;
      }
    }
    else if (path_flag & PATH_RAY_VOLUME_PASS) {
      /* Indirectly visible through volume. */
      pass_offset = (INTEGRATOR_STATE(state, path, bounce) == 1) ?
                        kernel_data.film.pass_volume_direct :
                        kernel_data.film.pass_volume_indirect;
    }
  }

  /* Single write call for GPU coherence. */
  if (pass_offset != PASS_UNUSED) {
    kernel_write_pass_float3(buffer + pass_offset, contribution);
  }
#endif /* __PASSES__ */
}

/* Write light contribution to render buffer. */
ccl_device_inline void kernel_accum_light(KernelGlobals kg,
                                          ConstIntegratorShadowState state,
                                          ccl_global float *ccl_restrict render_buffer)
{
  /* The throughput for shadow paths already contains the light shader evaluation. */
  float3 contribution = INTEGRATOR_STATE(state, shadow_path, throughput);
  kernel_accum_clamp(kg, &contribution, INTEGRATOR_STATE(state, shadow_path, bounce));

  const uint32_t render_pixel_index = INTEGRATOR_STATE(state, shadow_path, render_pixel_index);
  const uint64_t render_buffer_offset = (uint64_t)render_pixel_index *
                                        kernel_data.film.pass_stride;
  ccl_global float *buffer = render_buffer + render_buffer_offset;

  const uint32_t path_flag = INTEGRATOR_STATE(state, shadow_path, flag);
  const int sample = INTEGRATOR_STATE(state, shadow_path, sample);

  /* Ambient occlusion. */
  if (path_flag & PATH_RAY_SHADOW_FOR_AO) {
    if ((kernel_data.kernel_features & KERNEL_FEATURE_AO_PASS) && (path_flag & PATH_RAY_CAMERA)) {
      kernel_write_pass_float3(buffer + kernel_data.film.pass_ao, contribution);
    }
    if (kernel_data.kernel_features & KERNEL_FEATURE_AO_ADDITIVE) {
      const float3 ao_weight = INTEGRATOR_STATE(state, shadow_path, unshadowed_throughput);
      kernel_accum_combined_pass(kg, path_flag, sample, contribution * ao_weight, buffer);
    }
    return;
  }

  /* Direct light shadow. */
  kernel_accum_combined_pass(kg, path_flag, sample, contribution, buffer);

#ifdef __PASSES__
  if (kernel_data.film.light_pass_flag & PASS_ANY) {
    const uint32_t path_flag = INTEGRATOR_STATE(state, shadow_path, flag);

    /* Don't write any light passes for shadow catcher, for easier
     * compositing back together of the combined pass. */
    if (path_flag & PATH_RAY_SHADOW_CATCHER_HIT) {
      return;
    }

    /* Write lightgroup pass. LIGHTGROUP_NONE is ~0 so decode from unsigned to signed */
    const int lightgroup = (int)(INTEGRATOR_STATE(state, shadow_path, lightgroup)) - 1;
    if (lightgroup != LIGHTGROUP_NONE && kernel_data.film.pass_lightgroup != PASS_UNUSED) {
      kernel_write_pass_float3(buffer + kernel_data.film.pass_lightgroup + 3 * lightgroup,
                               contribution);
    }

    if (kernel_data.kernel_features & KERNEL_FEATURE_LIGHT_PASSES) {
      int pass_offset = PASS_UNUSED;

      if (path_flag & PATH_RAY_SURFACE_PASS) {
        /* Indirectly visible through reflection. */
        const float3 diffuse_weight = INTEGRATOR_STATE(state, shadow_path, pass_diffuse_weight);
        const float3 glossy_weight = INTEGRATOR_STATE(state, shadow_path, pass_glossy_weight);

        /* Glossy */
        const int glossy_pass_offset = ((INTEGRATOR_STATE(state, shadow_path, bounce) == 0) ?
                                            kernel_data.film.pass_glossy_direct :
                                            kernel_data.film.pass_glossy_indirect);
        if (glossy_pass_offset != PASS_UNUSED) {
          kernel_write_pass_float3(buffer + glossy_pass_offset, glossy_weight * contribution);
        }

        /* Transmission */
        const int transmission_pass_offset = ((INTEGRATOR_STATE(state, shadow_path, bounce) == 0) ?
                                                  kernel_data.film.pass_transmission_direct :
                                                  kernel_data.film.pass_transmission_indirect);

        if (transmission_pass_offset != PASS_UNUSED) {
          /* Transmission is what remains if not diffuse and glossy, not stored explicitly to save
           * GPU memory. */
          const float3 transmission_weight = one_float3() - diffuse_weight - glossy_weight;
          kernel_write_pass_float3(buffer + transmission_pass_offset,
                                   transmission_weight * contribution);
        }

        /* Reconstruct diffuse subset of throughput. */
        pass_offset = (INTEGRATOR_STATE(state, shadow_path, bounce) == 0) ?
                          kernel_data.film.pass_diffuse_direct :
                          kernel_data.film.pass_diffuse_indirect;
        if (pass_offset != PASS_UNUSED) {
          contribution *= diffuse_weight;
        }
      }
      else if (path_flag & PATH_RAY_VOLUME_PASS) {
        /* Indirectly visible through volume. */
        pass_offset = (INTEGRATOR_STATE(state, shadow_path, bounce) == 0) ?
                          kernel_data.film.pass_volume_direct :
                          kernel_data.film.pass_volume_indirect;
      }

      /* Single write call for GPU coherence. */
      if (pass_offset != PASS_UNUSED) {
        kernel_write_pass_float3(buffer + pass_offset, contribution);
      }
    }

    /* Write shadow pass. */
    if (kernel_data.film.pass_shadow != PASS_UNUSED && (path_flag & PATH_RAY_SHADOW_FOR_LIGHT) &&
        (path_flag & PATH_RAY_TRANSPARENT_BACKGROUND)) {
      const float3 unshadowed_throughput = INTEGRATOR_STATE(
          state, shadow_path, unshadowed_throughput);
      const float3 shadowed_throughput = INTEGRATOR_STATE(state, shadow_path, throughput);
      const float3 shadow = safe_divide(shadowed_throughput, unshadowed_throughput) *
                            kernel_data.film.pass_shadow_scale;
      kernel_write_pass_float3(buffer + kernel_data.film.pass_shadow, shadow);
    }
  }
#endif
}

/* Write transparency to render buffer.
 *
 * Note that we accumulate transparency = 1 - alpha in the render buffer.
 * Otherwise we'd have to write alpha on path termination, which happens
 * in many places. */
ccl_device_inline void kernel_accum_transparent(KernelGlobals kg,
                                                ConstIntegratorState state,
                                                const uint32_t path_flag,
                                                const float transparent,
                                                ccl_global float *ccl_restrict buffer)
{
  if (kernel_data.film.light_pass_flag & PASSMASK(COMBINED)) {
    kernel_write_pass_float(buffer + kernel_data.film.pass_combined + 3, transparent);
  }

  kernel_accum_shadow_catcher_transparent_only(kg, path_flag, transparent, buffer);
}

/* Write holdout to render buffer. */
ccl_device_inline void kernel_accum_holdout(KernelGlobals kg,
                                            ConstIntegratorState state,
                                            const uint32_t path_flag,
                                            const float transparent,
                                            ccl_global float *ccl_restrict render_buffer)
{
  ccl_global float *buffer = kernel_accum_pixel_render_buffer(kg, state, render_buffer);
  kernel_accum_transparent(kg, state, path_flag, transparent, buffer);
}

/* Write background contribution to render buffer.
 *
 * Includes transparency, matching kernel_accum_transparent. */
ccl_device_inline void kernel_accum_background(KernelGlobals kg,
                                               ConstIntegratorState state,
                                               const float3 L,
                                               const float transparent,
                                               const bool is_transparent_background_ray,
                                               ccl_global float *ccl_restrict render_buffer)
{
  float3 contribution = float3(INTEGRATOR_STATE(state, path, throughput)) * L;
  kernel_accum_clamp(kg, &contribution, INTEGRATOR_STATE(state, path, bounce) - 1);

  ccl_global float *buffer = kernel_accum_pixel_render_buffer(kg, state, render_buffer);
  const uint32_t path_flag = INTEGRATOR_STATE(state, path, flag);

  if (is_transparent_background_ray) {
    kernel_accum_transparent(kg, state, path_flag, transparent, buffer);
  }
  else {
    const int sample = INTEGRATOR_STATE(state, path, sample);
    kernel_accum_combined_transparent_pass(
        kg, path_flag, sample, contribution, transparent, buffer);
  }
  kernel_accum_emission_or_background_pass(kg,
                                           state,
                                           contribution,
                                           buffer,
                                           kernel_data.film.pass_background,
                                           kernel_data.background.lightgroup);
}

/* Write emission to render buffer. */
ccl_device_inline void kernel_accum_emission(KernelGlobals kg,
                                             ConstIntegratorState state,
                                             const float3 L,
                                             ccl_global float *ccl_restrict render_buffer,
                                             const int lightgroup = LIGHTGROUP_NONE)
{
  float3 contribution = L;
  kernel_accum_clamp(kg, &contribution, INTEGRATOR_STATE(state, path, bounce) - 1);

  ccl_global float *buffer = kernel_accum_pixel_render_buffer(kg, state, render_buffer);
  const uint32_t path_flag = INTEGRATOR_STATE(state, path, flag);
  const int sample = INTEGRATOR_STATE(state, path, sample);

  kernel_accum_combined_pass(kg, path_flag, sample, contribution, buffer);
  kernel_accum_emission_or_background_pass(
      kg, state, contribution, buffer, kernel_data.film.pass_emission, lightgroup);
}

CCL_NAMESPACE_END
