#ifndef ENGINE_INCLUDE_GFX_H_
#define ENGINE_INCLUDE_GFX_H_

#include <cstdint>
#include <functional>
#include <type_traits>
#include <vector>

// Enums and structs for the graphics abstraction

namespace engine {
namespace gfx {

// handles (incomplete types)
struct Pipeline;
struct UniformBuffer;
struct Buffer;
struct DrawBuffer;
struct DescriptorSetLayout;
struct DescriptorSet;
struct Image;
struct Sampler;

enum class MSAALevel {
  kOff,
  k2X,
  k4X,
  k8X,
  k16X,
};

struct GraphicsSettings {
  
  GraphicsSettings()
  {
    // sane defaults
    enable_validation = true;
    vsync = true;
    // not all GPUs/drivers support immediate present with V-sync enabled
    wait_for_present = true;
    msaa_level = MSAALevel::kOff;
  }

  bool enable_validation;
  bool vsync;
  // idle CPU after render until the frame has been presented
  // (no affect with V-sync disabled)
  bool wait_for_present;
  MSAALevel msaa_level;

};

enum class ShaderType {
  kVertex,
  kFragment,
};

enum class BufferType {
  kVertex,
  kIndex,
  kUniform,
};

enum class Primitive {
  kPoints,
  kLines,
  kLineStrip,
  kTriangles,
  kTriangleStrip,
};

enum class VertexAttribFormat {
  kFloat2,
  kFloat3,
  kFloat4
};

enum class Filter : int {
  kLinear,
  kNearest,
};

enum class DescriptorType {
  kUniformBuffer,
  kCombinedImageSampler,
};

namespace ShaderStageFlags {
  enum Bits : uint32_t {
    kVertex = 1 << 0,
    kFragment = 1 << 1,
  };
  typedef std::underlying_type<Bits>::type Flags;
}

struct VertexAttribDescription {
  VertexAttribDescription(uint32_t location, VertexAttribFormat format,
                          uint32_t offset) :
      location(location),
      format(format),
      offset(offset) {}
  uint32_t location; // the index to use in the shader
  VertexAttribFormat format;
  uint32_t offset;
};

struct VertexFormat {
  uint32_t stride;
  std::vector<VertexAttribDescription> attribute_descriptions;
};

struct PipelineInfo {
  const char* vert_shader_path;
  const char* frag_shader_path;
  VertexFormat vertex_format;
  bool alpha_blending;
  bool backface_culling;
  std::vector<const DescriptorSetLayout*> descriptor_set_layouts;
};

struct DescriptorSetLayoutBinding {
  DescriptorType descriptor_type = DescriptorType::kUniformBuffer;
  ShaderStageFlags::Flags stage_flags = 0;
};

struct SamplerInfo {
  Filter minify;
  Filter magnify;
  Filter mipmap;
  bool anisotropic_filtering;

  bool operator==(const SamplerInfo&) const = default;
};

}  // namespace gfx
}  // namespace engine

namespace std {
template<>
struct std::hash<engine::gfx::SamplerInfo>
{
  std::size_t operator()(const engine::gfx::SamplerInfo& k) const
  {
    using std::hash;
    
    size_t h1 = hash<int>()(static_cast<int>(k.minify));
    size_t h2 = hash<int>()(static_cast<int>(k.magnify));
    size_t h3 = hash<int>()(static_cast<int>(k.mipmap));
    size_t h4 = hash<bool>()(k.anisotropic_filtering);

    return ((h1 & 0xFF) << 24) |
           ((h2 & 0xFF) << 16) |
           ((h3 & 0xFF) << 8) |
           ((h4 & 0xFF) << 0);
  }
};

}  // namespace std

#endif