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));
}

@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;
}

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