// Copyright 2013 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "impeller/entity/contents/runtime_effect_contents.h"

#include <future>
#include <memory>

#include "flutter/fml/logging.h"
#include "flutter/fml/make_copyable.h"
#include "impeller/base/validation.h"
#include "impeller/core/formats.h"
#include "impeller/core/runtime_types.h"
#include "impeller/core/shader_types.h"
#include "impeller/entity/contents/content_context.h"
#include "impeller/entity/runtime_effect.vert.h"
#include "impeller/renderer/capabilities.h"
#include "impeller/renderer/pipeline_library.h"
#include "impeller/renderer/render_pass.h"
#include "impeller/renderer/shader_function.h"

namespace impeller {

void RuntimeEffectContents::SetRuntimeStage(
    std::shared_ptr<RuntimeStage> runtime_stage) {
  runtime_stage_ = std::move(runtime_stage);
}

void RuntimeEffectContents::SetUniformData(
    std::shared_ptr<std::vector<uint8_t>> uniform_data) {
  uniform_data_ = std::move(uniform_data);
}

void RuntimeEffectContents::SetTextureInputs(
    std::vector<TextureInput> texture_inputs) {
  texture_inputs_ = std::move(texture_inputs);
}

bool RuntimeEffectContents::CanInheritOpacity(const Entity& entity) const {
  return false;
}

static ShaderType GetShaderType(RuntimeUniformType type) {
  switch (type) {
    case kSampledImage:
      return ShaderType::kSampledImage;
    case kFloat:
      return ShaderType::kFloat;
    case kStruct:
      return ShaderType::kStruct;
  }
}

static std::shared_ptr<ShaderMetadata> MakeShaderMetadata(
    const RuntimeUniformDescription& uniform) {
  auto metadata = std::make_shared<ShaderMetadata>();
  metadata->name = uniform.name;
  metadata->members.emplace_back(ShaderStructMemberMetadata{
      .type = GetShaderType(uniform.type),
      .size = uniform.GetSize(),
      .byte_length = uniform.bit_width / 8,
  });

  return metadata;
}

bool RuntimeEffectContents::Render(const ContentContext& renderer,
                                   const Entity& entity,
                                   RenderPass& pass) const {
  const std::shared_ptr<Context>& context = renderer.GetContext();
  const std::shared_ptr<ShaderLibrary>& library = context->GetShaderLibrary();

  //--------------------------------------------------------------------------
  /// Get or register shader.
  ///

  // TODO(113719): Register the shader function earlier.

  std::shared_ptr<const ShaderFunction> function = library->GetFunction(
      runtime_stage_->GetEntrypoint(), ShaderStage::kFragment);

  //--------------------------------------------------------------------------
  /// Resolve runtime stage function.
  ///

  if (function && runtime_stage_->IsDirty()) {
    renderer.ClearCachedRuntimeEffectPipeline(runtime_stage_->GetEntrypoint());
    context->GetPipelineLibrary()->RemovePipelinesWithEntryPoint(function);
    library->UnregisterFunction(runtime_stage_->GetEntrypoint(),
                                ShaderStage::kFragment);

    function = nullptr;
  }

  if (!function) {
    std::promise<bool> promise;
    auto future = promise.get_future();

    library->RegisterFunction(
        runtime_stage_->GetEntrypoint(),
        ToShaderStage(runtime_stage_->GetShaderStage()),
        runtime_stage_->GetCodeMapping(),
        fml::MakeCopyable([promise = std::move(promise)](bool result) mutable {
          promise.set_value(result);
        }));

    if (!future.get()) {
      VALIDATION_LOG << "Failed to build runtime effect (entry point: "
                     << runtime_stage_->GetEntrypoint() << ")";
      return false;
    }

    function = library->GetFunction(runtime_stage_->GetEntrypoint(),
                                    ShaderStage::kFragment);
    if (!function) {
      VALIDATION_LOG
          << "Failed to fetch runtime effect function immediately after "
             "registering it (entry point: "
          << runtime_stage_->GetEntrypoint() << ")";
      return false;
    }

    runtime_stage_->SetClean();
  }

  //--------------------------------------------------------------------------
  /// Set up the command. Defer setting up the pipeline until the descriptor set
  /// layouts are known from the uniforms.
  ///

  const std::shared_ptr<const Capabilities>& caps = context->GetCapabilities();
  const auto color_attachment_format = caps->GetDefaultColorFormat();
  const auto stencil_attachment_format = caps->GetDefaultDepthStencilFormat();

  using VS = RuntimeEffectVertexShader;

  //--------------------------------------------------------------------------
  /// Fragment stage uniforms.
  ///

  std::vector<DescriptorSetLayout> descriptor_set_layouts;

  BindFragmentCallback bind_callback = [this, &renderer, &context,
                                        &descriptor_set_layouts](
                                           RenderPass& pass) {
    size_t minimum_sampler_index = 100000000;
    size_t buffer_index = 0;
    size_t buffer_offset = 0;

    for (const auto& uniform : runtime_stage_->GetUniforms()) {
      std::shared_ptr<ShaderMetadata> metadata = MakeShaderMetadata(uniform);

      switch (uniform.type) {
        case kSampledImage: {
          // Sampler uniforms are ordered in the IPLR according to their
          // declaration and the uniform location reflects the correct offset to
          // be mapped to - except that it may include all proceeding float
          // uniforms. For example, a float sampler that comes after 4 float
          // uniforms may have a location of 4. To convert to the actual offset
          // we need to find the largest location assigned to a float uniform
          // and then subtract this from all uniform locations. This is more or
          // less the same operation we previously performed in the shader
          // compiler.
          minimum_sampler_index =
              std::min(minimum_sampler_index, uniform.location);
          break;
        }
        case kFloat: {
          FML_DCHECK(renderer.GetContext()->GetBackendType() !=
                     Context::BackendType::kVulkan)
              << "Uniform " << uniform.name
              << " had unexpected type kFloat for Vulkan backend.";
          size_t alignment =
              std::max(uniform.bit_width / 8, DefaultUniformAlignment());
          auto buffer_view = renderer.GetTransientsBuffer().Emplace(
              uniform_data_->data() + buffer_offset, uniform.GetSize(),
              alignment);

          ShaderUniformSlot uniform_slot;
          uniform_slot.name = uniform.name.c_str();
          uniform_slot.ext_res_0 = uniform.location;
          pass.BindResource(ShaderStage::kFragment,
                            DescriptorType::kUniformBuffer, uniform_slot,
                            metadata, buffer_view);
          buffer_index++;
          buffer_offset += uniform.GetSize();
          break;
        }
        case kStruct: {
          FML_DCHECK(renderer.GetContext()->GetBackendType() ==
                     Context::BackendType::kVulkan);
          descriptor_set_layouts.emplace_back(DescriptorSetLayout{
              static_cast<uint32_t>(uniform.location),
              DescriptorType::kUniformBuffer,
              ShaderStage::kFragment,
          });
          ShaderUniformSlot uniform_slot;
          uniform_slot.name = uniform.name.c_str();
          uniform_slot.binding = uniform.location;

          std::vector<float> uniform_buffer;
          uniform_buffer.reserve(uniform.struct_layout.size());
          size_t uniform_byte_index = 0u;
          for (const auto& byte_type : uniform.struct_layout) {
            if (byte_type == 0) {
              uniform_buffer.push_back(0.f);
            } else if (byte_type == 1) {
              uniform_buffer.push_back(reinterpret_cast<float*>(
                  uniform_data_->data())[uniform_byte_index++]);
            } else {
              FML_UNREACHABLE();
            }
          }

          size_t alignment = std::max(sizeof(float) * uniform_buffer.size(),
                                      DefaultUniformAlignment());

          auto buffer_view = renderer.GetTransientsBuffer().Emplace(
              reinterpret_cast<const void*>(uniform_buffer.data()),
              sizeof(float) * uniform_buffer.size(), alignment);
          pass.BindResource(ShaderStage::kFragment,
                            DescriptorType::kUniformBuffer, uniform_slot,
                            ShaderMetadata{}, buffer_view);
        }
      }
    }

    size_t sampler_index = 0;
    for (const auto& uniform : runtime_stage_->GetUniforms()) {
      std::shared_ptr<ShaderMetadata> metadata = MakeShaderMetadata(uniform);

      switch (uniform.type) {
        case kSampledImage: {
          FML_DCHECK(sampler_index < texture_inputs_.size());
          auto& input = texture_inputs_[sampler_index];

          const std::unique_ptr<const Sampler>& sampler =
              context->GetSamplerLibrary()->GetSampler(
                  input.sampler_descriptor);

          SampledImageSlot image_slot;
          image_slot.name = uniform.name.c_str();

          uint32_t sampler_binding_location = 0u;
          if (!descriptor_set_layouts.empty()) {
            sampler_binding_location =
                descriptor_set_layouts.back().binding + 1;
          }

          descriptor_set_layouts.emplace_back(DescriptorSetLayout{
              sampler_binding_location,
              DescriptorType::kSampledImage,
              ShaderStage::kFragment,
          });

          image_slot.binding = sampler_binding_location;
          image_slot.texture_index = uniform.location - minimum_sampler_index;
          pass.BindResource(ShaderStage::kFragment,
                            DescriptorType::kSampledImage, image_slot,
                            *metadata, input.texture, sampler);

          sampler_index++;
          break;
        }
        default:
          continue;
      }
    }
    return true;
  };

  /// Now that the descriptor set layouts are known, get the pipeline.

  PipelineBuilderCallback pipeline_callback = [&](ContentContextOptions
                                                      options) {
    // Pipeline creation callback for the cache handler to call.
    auto create_callback =
        [&]() -> std::shared_ptr<Pipeline<PipelineDescriptor>> {
      PipelineDescriptor desc;
      desc.SetLabel("Runtime Stage");
      desc.AddStageEntrypoint(
          library->GetFunction(VS::kEntrypointName, ShaderStage::kVertex));
      desc.AddStageEntrypoint(library->GetFunction(
          runtime_stage_->GetEntrypoint(), ShaderStage::kFragment));
      auto vertex_descriptor = std::make_shared<VertexDescriptor>();
      vertex_descriptor->SetStageInputs(VS::kAllShaderStageInputs,
                                        VS::kInterleavedBufferLayout);
      vertex_descriptor->RegisterDescriptorSetLayouts(
          VS::kDescriptorSetLayouts);
      vertex_descriptor->RegisterDescriptorSetLayouts(
          descriptor_set_layouts.data(), descriptor_set_layouts.size());
      desc.SetVertexDescriptor(std::move(vertex_descriptor));
      desc.SetColorAttachmentDescriptor(
          0u, {.format = color_attachment_format, .blending_enabled = true});

      desc.SetStencilAttachmentDescriptors(StencilAttachmentDescriptor{});
      desc.SetStencilPixelFormat(stencil_attachment_format);

      desc.SetDepthStencilAttachmentDescriptor(DepthAttachmentDescriptor{});
      desc.SetDepthPixelFormat(stencil_attachment_format);

      options.ApplyToPipelineDescriptor(desc);
      auto pipeline = context->GetPipelineLibrary()->GetPipeline(desc).Get();
      if (!pipeline) {
        VALIDATION_LOG << "Failed to get or create runtime effect pipeline.";
        return nullptr;
      }

      return pipeline;
    };
    return renderer.GetCachedRuntimeEffectPipeline(
        runtime_stage_->GetEntrypoint(), options, create_callback);
  };

  return ColorSourceContents::DrawPositions<VS>(renderer, entity, pass,
                                                pipeline_callback,
                                                VS::FrameInfo{}, bind_callback);
}

}  // namespace impeller