struct MVP {
  float4x4 projection;
  float4x4 view;
  float4x4 model;
}

struct Uniforms {
  MVP mvp;
  float4 u_Color;
  bool u_HasTexture;
  Sampler2D u_Texture;
};

struct AssembledVertex {
  float3 position : POSITION;
  float2 texcoord : TEXCOORD;
};

struct Fragment {
  float4 color;
};

struct VertexStageOutput {
  float2 uv : UV;
  float4 sv_position : SV_Position;
};

float4 someFunction(float4 color) {
  return color * float4(0.5, 0.5, 0.5, 1.0);
}

[shader("vertex")]
VertexStageOutput vertexMain(
  uniform ParameterBlock<Uniforms> uniforms,
  AssembledVertex assembledVertex
) {
  VertexStageOutput output;

  float3 position = assembledVertex.position;

  output.uv = assembledVertex.texcoord;

  output.sv_position = mul(
    float4(position, 1.0),
    mul(uniforms.mvp.model, mul(uniforms.mvp.view, uniforms.mvp.projection))
  );

  return output;
}

[shader("fragment")]
Fragment fragmentMain(
  uniform ParameterBlock<Uniforms> uniforms,
  float2 uv: UV
) : SV_Target {
  Fragment output;
  if(uniforms.u_HasTexture) {
    output.color = uniforms.u_Texture.Sample(uv) * uniforms.u_Color;
  } else {
      output.color = someFunction(uniforms.u_Color);
  }
  return output;
}