struct VSInput
{
  float3 Position : POSITION0;
  float3 Normal : NORMAL0;
  float3 Texture : TEXCOORD0;
};

struct VSOutput
{
  float4 Position : SV_POSITION;
  float3 Normal : NORMAL0;
  float2 Texture : TEXCOORD0;
  float3 LightDirection : NORMAL1;
  float3 ViewDirection : NORMAL2;
  nointerpolation int MaterialIndex : materialindex;
};

struct VSShadowOutput
{
  float4 Position : SV_POSITION;
};

struct Node
{
  column_major float4x4 World;
};

struct Scene
{
  column_major float4x4 Projection;
  column_major float4x4 View;
  column_major float4x4 ShadowProjection;
  column_major float4x4 ShadowView;
  float4 LightPosition; // view space
};

struct MaterialColor
{
  float4 Emission;
  float4 Ambient;
  float4 Diffuse;
  float4 Specular;
};

// set 0: per-frame
[[vk::binding(0, 0)]] ConstantBuffer<Scene> Scene;
[[vk::binding(1, 0)]] StructuredBuffer<Node> Nodes;

// set 1: constant
[[vk::binding(0, 1)]] StructuredBuffer<MaterialColor> MaterialColors;

struct PushConstant {
  int NodeIndex;
  int MaterialIndex;
};

[[vk::push_constant]] PushConstant constants;

float4 getView(float4x4 view, float3 position)
{
  float4x4 world = Nodes[constants.NodeIndex].World;
  return mul(view, mul(world, float4(position.xyz, 1.0)));
}

float4 getProjection(float4x4 projection, float4 viewPosition)
{
  return mul(projection, viewPosition) * float4(-1, -1, 1, 1);
}

[shader("vertex")]
VSOutput VSMain(VSInput input)
{
  float4 viewPosition = getView(Scene.View, input.Position);

  VSOutput output = (VSOutput)0;
  output.Position = getProjection(Scene.Projection, viewPosition);
  output.Normal = mul((float3x3)Scene.View, mul((float3x3)Nodes[constants.NodeIndex].World, input.Normal));
  output.Texture = input.Texture.xy * 1.0;

  output.LightDirection = (Scene.LightPosition - viewPosition).xyz;
  output.ViewDirection = -viewPosition.xyz;

  return output;
}

[shader("pixel")]
float4 PSMain(VSOutput input) : SV_TARGET
{
  //float3 color = texture.Sample(samplers[0], input.Texture).bgr;
  float4 diffuseColor = MaterialColors[constants.MaterialIndex].Diffuse;
  float4 specularColor = MaterialColors[constants.MaterialIndex].Specular;
  float4 emissionColor = MaterialColors[constants.MaterialIndex].Emission;

  float3 N = normalize(input.Normal);
  float3 L = normalize(input.LightDirection);
  float3 V = normalize(input.ViewDirection);
  float3 R = reflect(-L, N);

  const float a = 16.0;
  const float specularIntensity = 0.8;
  float3 specular = pow(max(dot(R, V), 0), a) * specularIntensity;
  float3 diffuse = max(dot(N, L), 0.001);

  return float4(diffuse * diffuseColor.xyz + specular * specularColor.xyz + emissionColor.xyz, 1.0);
}

[shader("vertex")]
VSShadowOutput VSShadowMain(VSInput input)
{
  float4 viewPosition = getView(Scene.ShadowView, input.Position);

  VSShadowOutput output = (VSShadowOutput)0;
  output.Position = getProjection(Scene.ShadowProjection, viewPosition);
  return output;
}

[shader("pixel")]
void PSShadowMain(VSShadowOutput input)
{
}