#version 430

layout (binding = 0) uniform sampler2D worldPositionSamp;
layout (binding = 1) uniform sampler2D worldNormalSamp;
layout (binding = 2) uniform sampler2D worldColorSamp;
layout (binding = 3) uniform sampler2D worldDepthSamp;
layout (binding = 4) uniform sampler2D ssaoNoise;

const int numberOfSamples = 64;
const vec3 ssaoKernel[64] =
{
    vec3( 0.009,  0.006, -0.007), vec3( 0.008, -0.003,  0.014), vec3( 0.004, -0.005, -0.019), vec3( 0.016, -0.012, -0.014), 
    vec3(-0.022, -0.018, -0.007), vec3(-0.018, -0.028, -0.006), vec3( 0.023, -0.028,  0.016), vec3( 0.010, -0.044,  0.000), 
    vec3( 0.037, -0.035,  0.007), vec3( 0.028,  0.015, -0.048), vec3( 0.030, -0.023,  0.053), vec3(-0.003,  0.042,  0.059), 
    vec3( 0.077, -0.020, -0.010), vec3( 0.029, -0.053,  0.064), vec3( 0.043,  0.058, -0.064), vec3( 0.102,  0.004,  0.028), 
    vec3(-0.014, -0.110,  0.029), vec3(-0.019,  0.056, -0.110), vec3(-0.094,  0.019, -0.095), vec3(-0.092,  0.030, -0.108), 
    vec3(-0.072, -0.120,  0.070), vec3(-0.071,  0.091, -0.121), vec3(-0.096,  0.148, -0.033), vec3(-0.080,  0.160, -0.068), 
    vec3(-0.037,  0.189, -0.066), vec3( 0.024, -0.038, -0.212), vec3(-0.228, -0.018,  0.021), vec3(-0.169,  0.175,  0.007), 
    vec3( 0.064, -0.150,  0.200), vec3(-0.017, -0.156, -0.223), vec3(-0.092,  0.240,  0.128), vec3(-0.264, -0.140,  0.044), 
    vec3(-0.063, -0.311, -0.024), vec3(-0.232, -0.199,  0.136), vec3(-0.333, -0.005,  0.111), vec3( 0.245, -0.255,  0.099), 
    vec3( 0.214,  0.198, -0.251), vec3( 0.192, -0.325,  0.139), vec3(-0.270,  0.294, -0.131), vec3( 0.303, -0.281, -0.147), 
    vec3(-0.140, -0.275,  0.338), vec3( 0.387, -0.147,  0.237), vec3( 0.380, -0.260,  0.185), vec3(-0.172,  0.292, -0.390), 
    vec3( 0.307, -0.081, -0.433), vec3( 0.065, -0.492,  0.256), vec3( 0.224,  0.274, -0.458), vec3( 0.131, -0.370, -0.455), 
    vec3( 0.113, -0.508, -0.341), vec3(-0.012,  0.573,  0.295), vec3( 0.028, -0.417, -0.521), vec3(-0.555,  0.409, -0.037), 
    vec3(-0.372,  0.605,  0.075), vec3( 0.352, -0.567, -0.316), vec3( 0.507,  0.558,  0.118), vec3( 0.460,  0.548,  0.329), 
    vec3(-0.414, -0.391,  0.580), vec3( 0.792,  0.248, -0.122), vec3( 0.207, -0.654, -0.526), vec3( 0.223, -0.713, -0.485), 
    vec3(-0.333, -0.446, -0.729), vec3( 0.757,  0.249,  0.506), vec3(-0.896, -0.145, -0.349), vec3(-0.125, -0.870, -0.476)
};
uniform mat4 proj;
uniform mat4 view;

uniform int width;
uniform int height;
const float radius = 0.25;

in vec2 varTex;
out float color;

void main()
{     
    vec3 fragPos = texture(worldPositionSamp, varTex).xyz;
    vec3 random = texture(ssaoNoise, varTex * vec2(width * 0.25, height * 0.25)).xyz * radius * 0.25; 

    float occlusion = 0.0;
    for(int i = 0; i < numberOfSamples; i++)
    {
        vec4 projFragPos = proj * vec4(fragPos + ssaoKernel[i] * radius + random, 1.0);
        projFragPos.xyz /= projFragPos.w;
        projFragPos.xyz = projFragPos.xyz * 0.5 + 0.5;

        float depth1 = texture(worldDepthSamp, projFragPos.xy).x;
        float depth2 = projFragPos.z;

        float rangeCheck = float(abs(depth2 - depth1) < radius);
        occlusion += float(depth2 >= depth1) * rangeCheck;
    }
    color = 1 - occlusion / numberOfSamples;
}