////////////////////////////////////////////////////////////
//~ Rects

//////////////////////////////
//- Vertex shader

ImplVertexShader(UI_DRectVS, UI_DRectPSInput)
{
  UI_GpuParams params = G_SDeref<UI_GpuParams>(UI_GpuConst_Params)[0];
  StructuredBuffer<UI_GpuRect> rects = G_SDeref<UI_GpuRect>(params.rects);

  UI_GpuRect rect = rects[SV_InstanceID];
  Vec2 rect_uv = RectUvFromIdx(SV_VertexID);
  Vec2 tex_uv = lerp(rect.tex_slice_uv.p0, rect.tex_slice_uv.p1, rect_uv);
  Vec2 target_pos = lerp(rect.bounds.p0, rect.bounds.p1, rect_uv);

  UI_DRectPSInput result;
  {
    result.sv_position = Vec4(NdcFromPos(target_pos, Vec2(params.target_size).xy), 0, 1);
    result.base_background_premul = Premul(rect.background_lin);
    result.base_border_premul = Premul(rect.border_lin);
    result.tint_premul = Premul(rect.tint_lin);
    result.debug_premul = Premul(rect.debug_lin);
    result.rect_uv = rect_uv;
    result.tex_uv = tex_uv;
    result.rect = rect;
  }
  return result;
}

//////////////////////////////
//- Pixel shader

ImplPixelShader(UI_DRectPS, UI_DRectPSOutput, UI_DRectPSInput input)
{
  UI_GpuParams params = G_SDeref<UI_GpuParams>(UI_GpuConst_Params)[0];
  SamplerState sampler = G_SDeref(params.sampler);

  UI_GpuRect rect = input.rect;
  Vec2 rect_uv = input.rect_uv;
  Vec2 p = input.sv_position.xy;
  Vec2 p0 = rect.bounds.p0;
  Vec2 p1 = rect.bounds.p1;

  //- Compute rect dist (negative means pixel is inside of rect)
  f32 rect_dist = min(min(p.x - p0.x, p1.x - p.x), min(p.y - p0.y, p1.y - p.y));
  {
    f32 tl_radius = rect.tl_rounding;
    f32 tr_radius = rect.tr_rounding;
    f32 br_radius = rect.br_rounding;
    f32 bl_radius = rect.bl_rounding;
    Vec2 tl = Vec2(p0.x + tl_radius, p0.y + tl_radius);
    Vec2 tr = Vec2(p1.x - tr_radius, p0.y + tr_radius);
    Vec2 br = Vec2(p1.x - br_radius, p1.y - br_radius);
    Vec2 bl = Vec2(p0.x + bl_radius, p1.y - bl_radius);
    if (p.x < tl.x && p.y < tl.y) { rect_dist = min(rect_dist, tl_radius - length(tl - p)); }
    if (p.x > tr.x && p.y < tr.y) { rect_dist = min(rect_dist, tr_radius - length(tr - p)); }
    if (p.x > br.x && p.y > br.y) { rect_dist = min(rect_dist, br_radius - length(br - p)); }
    if (p.x < bl.x && p.y > bl.y) { rect_dist = min(rect_dist, bl_radius - length(bl - p)); }
  }
  rect_dist = -rect_dist;
  f32 rect_dist_fwidth = saturate(fwidth(rect_dist));

  bool is_inside = rect_dist < 0;

  //- Compute background color
  Vec4 background_premul = 0;
  if (is_inside)
  {
    if (G_IsRefNil(rect.tex))
    {
      background_premul = input.base_background_premul;
    }
    else
    {
      Texture2D<Vec4> tex = G_VDeref<Vec4>(rect.tex);
      background_premul = tex.SampleLevel(sampler, input.tex_uv, 0);
      background_premul.rgb *= background_premul.a;
    }
  }

  //- Compute borer color
  Vec4 border_premul = input.base_border_premul;

  //- Compute border dist
  f32 border_dist = 0;
  border_dist = abs(rect_dist);
  if (is_inside)
  {
    border_dist -= rect.border_size;
  }

  //- Compute anti-aliased border-over-background color
  Vec4 composite_premul = 0;
  {
    f32 smoothness = rect_dist_fwidth * params.aa * 0.5;
    f32 border_coverage = smoothstep(smoothness, -smoothness, border_dist);
    composite_premul = lerp(background_premul, border_premul, border_coverage);
  }

  //- Finalize
  Vec4 result = composite_premul * input.tint_premul;
  if (UI_GpuConst_DebugDraw)
  {
    result = input.debug_premul;
  }

  UI_DRectPSOutput output;
  output.sv_target0 = result;
  return output;
}

////////////////////////////////////////////////////////////
//~ Blit

//////////////////////////////
//- Vertex shader

ImplVertexShader(UI_BlitVS, UI_BlitPSInput)
{
  Vec2 uv = RectUvFromIdx(SV_VertexID);
  UI_BlitPSInput result;
  result.sv_position = Vec4(NdcFromUv(uv).xy, 0, 1);
  result.src_uv = uv;

  return result;
}

//////////////////////////////
//- Pixel shader

ImplPixelShader(UI_BlitPS, UI_BlitPSOutput, UI_BlitPSInput input)
{
  UI_GpuParams params = G_SDeref<UI_GpuParams>(UI_GpuConst_Params)[0];
  Texture2D<Vec4> tex = G_SDeref<Vec4>(params.target_ro);
  SamplerState sampler = G_SDeref(params.sampler);

  Vec2 uv = input.src_uv;
  Vec4 result = tex.Sample(sampler, uv);

  UI_BlitPSOutput output;
  output.sv_target0 = result;
  return output;
}