// Copyright(c) 2019, NVIDIA CORPORATION. All rights reserved.
//
// 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.
//

#include "shaders.hpp"
#include "vulkan/vulkan.hpp"
#include "StandAlone/ResourceLimits.h"
#include "SPIRV/GlslangToSpv.h"

namespace vk
{
  namespace su
  {

    EShLanguage translateShaderStage(vk::ShaderStageFlagBits stage)
    {
      switch (stage)
      {
        case vk::ShaderStageFlagBits::eVertex:                  return EShLangVertex;
        case vk::ShaderStageFlagBits::eTessellationControl:     return EShLangTessControl;
        case vk::ShaderStageFlagBits::eTessellationEvaluation:  return EShLangTessEvaluation;
        case vk::ShaderStageFlagBits::eGeometry:                return EShLangGeometry;
        case vk::ShaderStageFlagBits::eFragment:                return EShLangFragment;
        case vk::ShaderStageFlagBits::eCompute:                 return EShLangCompute;
        default:
          assert(false && "Unknown shader stage");
          return EShLangVertex;
      }
    }

    bool GLSLtoSPV(const vk::ShaderStageFlagBits shaderType, std::string const& glslShader, std::vector<unsigned int> &spvShader)
    {
      EShLanguage stage = translateShaderStage(shaderType);

      const char *shaderStrings[1];
      shaderStrings[0] = glslShader.data();

      glslang::TShader shader(stage);
      shader.setStrings(shaderStrings, 1);

      // Enable SPIR-V and Vulkan rules when parsing GLSL
      EShMessages messages = (EShMessages)(EShMsgSpvRules | EShMsgVulkanRules);

      if (!shader.parse(&glslang::DefaultTBuiltInResource, 100, false, messages))
      {
        puts(shader.getInfoLog());
        puts(shader.getInfoDebugLog());
        return false;  // something didn't work
      }

      glslang::TProgram program;
      program.addShader(&shader);

      //
      // Program-level processing...
      //

      if (!program.link(messages))
      {
        puts(shader.getInfoLog());
        puts(shader.getInfoDebugLog());
        fflush(stdout);
        return false;
      }

      glslang::GlslangToSpv(*program.getIntermediate(stage), spvShader);
      return true;
    }

    vk::UniqueShaderModule createShaderModule(vk::UniqueDevice &device, vk::ShaderStageFlagBits shaderStage, std::string const& shaderText)
    {
      std::vector<unsigned int> shaderSPV;
      bool ok = GLSLtoSPV(shaderStage, shaderText, shaderSPV);
      assert(ok);

      return device->createShaderModuleUnique(vk::ShaderModuleCreateInfo(vk::ShaderModuleCreateFlags(), shaderSPV.size() * sizeof(unsigned int), shaderSPV.data()));
    }
  }
}