/*
    Copyright (c) 2024 Josh Britain (jbritain)
    Licensed under the MIT license

      _____   __   _                          
     / ___/  / /  (_)  __ _   __ _  ___   ____
    / (_ /  / /  / /  /  ' \ /  ' \/ -_) / __/
    \___/  /_/  /_/  /_/_/_//_/_/_/\__/ /_/   
    
    By jbritain
    https://jbritain.net
                                            
*/

#include "/lib/common.glsl"

#ifdef vsh

out vec2 texcoord;

void main() {
  gl_Position = ftransform();
  texcoord = (gl_TextureMatrix[0] * gl_MultiTexCoord0).xy;
}

#endif

// ===========================================================================================

#ifdef fsh
in vec2 texcoord;

#include "/lib/dh.glsl"
#include "/lib/util/packing.glsl"

/* RENDERTARGETS: 0 */
layout(location = 0) out vec4 color;

void main() {
  color = texture(colortex0, texcoord);

  #if defined DISTANT_HORIZONS && defined DH_AO
  float depth = texture(depthtex0, texcoord).r;
  vec3 viewPos = vec3(0.0);
  if (depth != 1.0) {
    return;
  }

  dhOverride(depth, viewPos, false);
  if (depth == 1.0) {
    return;
  }

  vec3 worldNormal = decodeNormal(texture(colortex1, texcoord).xy);
  vec3 normal = mat3(gbufferModelView) * worldNormal;

  mat3 tbn;
  tbn[2] = normal;
  tbn[0] = normal.yzx;
  tbn[1] = cross(tbn[0], tbn[2]);

  float occlusion = 0.0;

  for (int i = 0; i < DH_AO_SAMPLES; i++) {
    vec4 noise = blueNoise(texcoord, i + frameCounter * DH_AO_SAMPLES);

    float scale = i / float(DH_AO_SAMPLES);
    scale = mix(0.1, 1.0, pow2(scale));

    vec3 hemisphereDir =
      normalize(vec3(noise.x * 2.0 - 1.0, noise.y * 2.0 - 1.0, noise.z)) *
      noise.w *
      scale;

    vec3 sampleOffset = tbn * hemisphereDir;
    vec3 sampleViewPos = viewPos + sampleOffset * DH_AO_RADIUS;

    vec4 sampleClipPos = dhProjection * vec4(sampleViewPos, 1.0);
    vec3 sampleScreenPos = sampleClipPos.xyz / sampleClipPos.w * 0.5 + 0.5;

    sampleScreenPos.z = texture(dhDepthTex0, sampleScreenPos.xy).r;
    sampleClipPos =
      dhProjectionInverse * vec4(sampleScreenPos * 2.0 - 1.0, 1.0);
    sampleViewPos = sampleClipPos.xyz / sampleClipPos.w;

    float rangeCheck = smoothstep(
      0.0,
      1.0,
      DH_AO_RADIUS / abs(viewPos.z - sampleViewPos.z)
    );
    occlusion += float(sampleViewPos.z >= viewPos.z + DH_AO_BIAS) * rangeCheck;
  }

  occlusion /= DH_AO_SAMPLES;

  color.rgb *= 1.0 - occlusion * ambientOcclusionLevel;
  #endif

}

#endif
