struct CameraUniform {
  eye: vec4<f32>;
  vp: mat4x4<f32>;
};

struct VertexInput {
  [[location(0)]] position: vec3<f32>;
  [[location(1)]] tan_frame: u32;
};

struct VertexOutput {
  [[builtin(position)]] clip_position: vec4<f32>;
  [[location(0)]] position: vec3<f32>;
  [[location(1)]] color: vec3<f32>;
};

[[group(0), binding(0)]]
var<uniform> camera: CameraUniform;

fn random(seed: u32, salt: f32) -> f32 {
  return abs(sin((f32(seed & u32(0x11111)) * 0.7071 + salt) * 78.233));
}

[[stage(vertex)]]
fn vs_main(
  [[builtin(instance_index)]] mesh_idx: u32,
  [[builtin(vertex_index)]] vertex_idx: u32,
  vertex: VertexInput,
) -> VertexOutput {
  let world_pos = vertex.position;

  var out: VertexOutput;
  out.clip_position = camera.vp * vec4<f32>(world_pos, 1.0);
  out.position = world_pos;
  out.color.r = random(vertex_idx, f32(1.0) + world_pos.x);
  out.color.g = random(vertex_idx, f32(2.0) + world_pos.y);
  out.color.b = random(vertex_idx, f32(3.0) + world_pos.z);
  return out;
}

[[stage(fragment)]]
fn fs_main(
  frag: VertexOutput,
) -> [[location(0)]] vec4<f32> {
  return vec4<f32>(frag.color, 1.0);
}