#version 460 core

layout(local_size_x = 1, local_size_y = 1, local_size_z = 1) in;

struct ActiveClusters {
    uint clusterActive;
};

layout (std430, binding = 7) buffer clusterActive{
    ActiveClusters clusteractive[ ];
};

uniform uint tileSizeInPx; // How many pixels a rectangular cluster takes in x and y
uniform uvec3 numClusters; // The fixed number of clusters in x y and z axes
uniform float zNear;
uniform float zFar;
uniform vec2 screenDimensions;

uniform sampler2D depthtext;

float LinearizeDepth(float depth);
void markActiveClusters(vec2 pixelID, float z);
uint getClusterIndex(vec3 pixelCoord);
uint getDepthSlice(float depth);

void main() {
    ivec3 groupId = ivec3(gl_WorkGroupID);
    ivec3 localId = ivec3(gl_LocalInvocationID);
    ivec3 globalId = ivec3(gl_GlobalInvocationID);
    ivec3 coords = groupId * ivec3(gl_WorkGroupSize) + localId;
    ivec2 pixelCoord = ivec2(coords.xy);


    ivec2 ScreenCord = pixelCoord.xy / ivec2(screenDimensions.xy);

    float z = LinearizeDepth(texture(depthtext, ScreenCord).r / zFar);

    uint clusterID = getClusterIndex(vec3(pixelCoord.xy, z));
    clusteractive[clusterID].clusterActive == 1;
}


void markActiveClusters(vec2 pixelID, float z){
    uint clusterID = getClusterIndex(vec3(pixelID.xy, z));
    clusteractive[clusterID].clusterActive == 1;

}

uint getDepthSlice(float depth){
    float part1 = numClusters.z / log(zFar / zNear);
    float part2 = -(numClusters.z * log(zNear)) / log(zFar / zNear);
    uint clusterZvalue = uint(max(log(depth) * part1 + part2, 0.0f));

    return  clusterZvalue;
}
uint getClusterIndex(vec3 pixelCoord){
    uint clusterZVal  = getDepthSlice(pixelCoord.z);
    uvec3 clusters    = uvec3( uvec2( pixelCoord.xy / tileSizeInPx), clusterZVal);
    uint clusterIndex = clusters.x +
    numClusters.x * clusters.y +
    (numClusters.x * numClusters.y) * clusters.z;
    return clusterIndex;
}

float LinearizeDepth(float depth)
{
    float z = depth * 2.0 - 1.0; // Back to NDC
    return (2.0 * zNear * zFar) / (zFar + zNear - z * (zFar - zNear));
}