#version 450

layout(location = 0) in vec2 uv;
layout(location = 0) out vec4 out_color;
layout(set = 2, binding = 0) uniform sampler2D screen;

layout(std140, set = 3, binding = 0) uniform UniformBlock {
  mat4 model;
  mat4 view;
  mat4 proj;
  mat4 inv_view;
  mat4 inv_proj;
  vec4 cam_pos;
  float time;
  int post_mode;
  vec2 atlas_adjust;
};

float t(float x, float y) { return length(texture(screen, vec2(x, y)).xyz); }

mat3 neighborhood() {
  vec2 d = 1.0 / vec2(textureSize(screen, 0));
  return mat3(t(uv.x - d.x, uv.y - d.y), t(uv.x + 0.0, uv.y - d.y),
              t(uv.x + d.x, uv.y - d.y), t(uv.x - d.x, uv.y - 0.0),
              t(uv.x + 0.0, uv.y + 0.0), t(uv.x + d.x, uv.y - 0.0),
              t(uv.x - d.x, uv.y + d.y), t(uv.x + 0.0, uv.y + d.y),
              t(uv.x + d.x, uv.y + d.y));
}

float sum3(mat3 m) {
  float s = 0.0;
  for (int c = 0; c < 3; ++c) {
    vec3 col = m[c];
    s += col.x + col.y + col.z;
  }
  return s;
}

float f(mat3 kernel) {
  return abs(sum3(matrixCompMult(kernel, neighborhood())));
}


float brightness(vec3 color) {
  return dot(color, vec3(0.299, 0.587, 0.114));
}

float dither() {
  if(length(texture(screen, uv).xyz) == 0.0)
    return 0.0;
  vec2 coord = uv * textureSize(screen, 0).xy;

  int x = int(mod(coord.x, 4.0));
  int y = int(mod(coord.y, 4.0));
  int index = x + y * 4;

  float threshold[16] = float[](
    0.0/16.0,  8.0/16.0,  2.0/16.0, 10.0/16.0,
    12.0/16.0, 4.0/16.0, 14.0/16.0,  6.0/16.0,
    3.0/16.0, 11.0/16.0,  1.0/16.0,  9.0/16.0,
    15.0/16.0,7.0/16.0, 13.0/16.0,  5.0/16.0
  );

  vec3 color = texture(screen, uv).rgb;

  return brightness(color) < threshold[index] ? 0.0 : 1.0;
}


void main() {
  const mat3 sobelx = mat3(-1.0, -2.0, -1.0, 0.0, 0.0, 0.0, 1.0, 2.0, 1.0);

  const mat3 sobely = mat3(-1.0, 0.0, 1.0, -2.0, 0.0, 2.0, -1.0, 0.0, 1.0);

  switch(post_mode) {
    case 0:
      out_color = texture(screen, uv);
    break;
    case 1:
      out_color = vec4(brightness(texture(screen, uv).xyz) < 0.5? 0.0 : 1.0);
    break;
    case 2:
      out_color = vec4(dither());
    break;
  }
  return;

  out_color = out_color * 0.9 +
    0.1*((t(uv.x, uv.y) > 0.01)?
      vec4(abs(f(sobelx) + f(sobely))) : vec4(0.0));
}