#version 450 core
layout(location = 0) out vec4 oColor;

layout(std140, binding = 0) uniform PerFrame {
  mat4 uView;
  mat4 uProj;
  vec4 uLightDir;
};
layout(std140, binding = 2) uniform Material {
  vec4 uAlbedo; // rgb used, a padding
};

in VS_OUT {
  vec3 wPos;
  vec3 wNrm;
  vec2 uv;
  flat int hasNrm;
  flat int hasUV;
} v;

vec3 fallbackNormal(vec3 wPos) {
  vec3 dx = dFdx(wPos), dy = dFdy(wPos);
  vec3 c = cross(dx, dy);
  float l2 = dot(c, c);
  return (l2 < 1e-12) ? vec3(0, 0, 1) : normalize(c);
}

void main() {
  vec3 N = (v.hasNrm != 0) ? normalize(v.wNrm) : fallbackNormal(v.wPos);
  vec3 L = normalize(-uLightDir.xyz);
  float ndl = max(dot(N, L), 0.0);
  vec3 ambient = vec3(0.08);
  vec3 colorLinear = ambient + uAlbedo.rgb * ndl;
  oColor = vec4(pow(colorLinear, vec3(1.0/2.2)), 1.0);
}