#version 430

layout (binding = 1) uniform sampler2D worldPositionSamp;
layout (binding = 2) uniform sampler2D worldNormalSamp;
layout (binding = 3) uniform sampler2D worldColorSamp;
layout (binding = 4) uniform sampler2D worldDepthSamp;
layout (binding = 5) uniform sampler2D noiseSamp;
layout (binding = 6) uniform sampler2DShadow worldShadowSamp;

const float bias = 0.025;
uniform float radius;

// ssao kernel is pre generated for simplicity and performance
// for(int i = 0; i < ssaoKernelAmount; i++)
// {
//     vec3 v = (random(-1, 1), random(-1, 1), random(0, 1));
//     normalize(v);
//     v *= random(0, 1);
// 
//     float scale = (float) i / ssaoKernelAmount; 
//     scale  = 0.1f + (scale * scale) * 0.9f;
//     v *= scale;
// }

uniform int numberOfSamples;
const vec3 ssaoKernel[64] =
{
    vec3(0.0261425, -0.0376851, 4.00204e-07), vec3(-0.0517141, -0.0320865, 0.0304131), vec3(-0.0108267, 0.040398, 0.0315651), vec3(-0.0314388, -0.0327688, 0.0292523), vec3(-0.00132874, -0.0056109, 0.00382464), vec3(0.0297163, 0.062378, 0.0697156), vec3(-0.0489338, 0.00322945, 0.0507385), vec3(0.0689938, 0.0338294, 0.0349743), 
    vec3(0.0167713, -0.0321483, 0.00932237), vec3(0.0331278, 0.0172987, 0.0213404), vec3(0.0374994, 0.0812687, 0.0208025), vec3(0.0266481, -0.0865055, 0.0659467), vec3(0.0547641, -0.0130673, 0.0280206), vec3(-0.0110478, -0.01767, 0.00933272), vec3(0.00571618, 0.00555481, 0.00339805), vec3(0.001716, 0.000476389, 0.0476425), 
    vec3(-0.00607237, -0.000156404, 0.0128097), vec3(6.96767e-05, -0.0420028, 0.0466964), vec3(0.00540731, 0.0752215, 0.0251832), vec3(0.0514841, -0.0885747, 0.0926251), vec3(-0.0847474, -0.0655798, 0.0724548), vec3(0.0660382, 0.0362147, 0.121362), vec3(-0.0245497, 0.0357539, 0.0459818), vec3(0.084097, 0.0122515, 0.161992), 
    vec3(-0.0471186, 0.069756, 0.0420852), vec3(-0.0261632, -0.0039447, 0.0330319), vec3(0.00775989, 0.0018387, 0.00197227), vec3(0.167912, -0.000560453, 0.0985381), vec3(0.0578085, 0.180922, 0.128394), vec3(0.0217065, -0.0290399, 0.00807598), vec3(-0.111954, -0.0507763, 0.0102483), vec3(0.0672952, 0.0322446, 0.00206515), 
    vec3(0.187537, -0.0884211, 0.0438314), vec3(-0.0661418, 0.105045, 0.0435408), vec3(0.0592117, -0.239374, 0.169697), vec3(0.00562892, 0.045657, 0.0295806), vec3(-0.126569, -0.0322389, 0.173734), vec3(-0.105291, -0.0336205, 0.369015), vec3(-0.133294, -0.221413, 0.0464706), vec3(0.207733, 0.25832, 0.108203), 
    vec3(-0.0605341, -0.0128894, 0.0677724), vec3(-0.0119915, 0.0655307, 0.00231462), vec3(-0.262367, -0.063802, 0.337014), vec3(-0.144795, -0.114031, 0.0155575), vec3(0.141442, -0.182272, 0.0632041), vec3(0.437972, -0.0676212, 0.24775), vec3(0.196835, -0.312091, 0.357106), vec3(-0.0222231, 0.279056, 0.0967121), 
    vec3(0.141587, 0.175742, 0.166133), vec3(-0.0631059, 0.138069, 0.494785), vec3(0.479211, 0.198913, 0.33888), vec3(0.0271384, -0.152772, 0.308639), vec3(0.369594, -0.414181, 0.249154), vec3(0.38887, 0.241946, 0.231701), vec3(0.0066864, 0.00571323, 0.0110748), vec3(-0.00410669, 0.0027978, 0.0496037), 
    vec3(0.228858, -0.015091, 0.486861), vec3(0.470433, 0.535686, 0.128289), vec3(-0.0906902, -0.659009, 0.49676), vec3(-0.372504, -0.109116, 0.217853), vec3(-0.0523188, -0.0971253, 0.710221), vec3(0.116336, -0.0672402, 0.0425562), vec3(-0.000688899, 0.000160498, 0.00043486), vec3(-0.151823, 0.190876, 0.324663)
};
uniform mat4 projMatrix;

in vec2 varTextureCoord;
out float color;

uniform int width;
uniform int height;

void main()
{     
    vec3 fragPos = texture(worldPositionSamp, varTextureCoord).xyz;
    vec3 normal = texture(worldNormalSamp, varTextureCoord).rgb;
    vec3 randomVec = texture(noiseSamp, varTextureCoord * vec2(width / 4.0, height / 4.0)).xyz; 

    vec3 tangent = normalize(randomVec - normal * dot(randomVec, normal));
    vec3 bitangent = cross(normal, tangent);
    mat3 TBN = mat3(tangent, bitangent, normal);  

    float occlusion = 0.0;
    for(int i = 0; i < numberOfSamples; i++)
    {
        vec3 sampl = TBN * ssaoKernel[i]; // From tangent to view-space
        sampl = fragPos + sampl * radius; 

        vec4 offset = vec4(sampl, 1.0);
        offset = projMatrix * offset; // from view to clip-space
        offset.xyz /= offset.w; // perspective divide
        offset.xyz = offset.xyz * 0.5 + 0.5; // transform to range 0.0 - 1.0  

        float sampleDepth = texture(worldPositionSamp, offset.xy).z; 

        float rangeCheck = smoothstep(0.0, 1.0, radius / abs(fragPos.z - sampleDepth));
        occlusion += float(sampleDepth >= sampl.z + bias) * rangeCheck;   
    }  
    
    occlusion /= numberOfSamples;
    occlusion = 1 - occlusion;
    color = occlusion;

    //color = texture(worldDepthSamp, varTextureCoord).x;

    /*vec4 w = projMatrix * viewMatrix * vec4(texture(worldPositionSamp, varTextureCoord).xyz, 1.0);
    w = w * 0.5 + 0.5;
    float inShadow = textureProj(worldShadowSamp, w);
    color = 1 - inShadow * 0.5;*/
}