#version 460
#extension GL_EXT_buffer_reference : require
layout(local_size_x=64) in;
layout(buffer_reference,std430,buffer_reference_align=16) buffer Positions {
    vec4 data[];
};
layout(buffer_reference,std430,buffer_reference_align=4) buffer Indices {
    uint data[];
};
// range: vertex offset, index offset, vertex count, triangle count.
// identity: cluster ID, geometry ID, then two reserved zero components.
struct Cluster {
    uvec4 range;
    uvec4 identity;
};
layout(buffer_reference,std430,buffer_reference_align=16) buffer Clusters {
    Cluster data[];
};
layout(push_constant) uniform Generate {
    Positions positions;
    Indices indices;
    Clusters descriptions;
    uint columns;
    uint rows;
    float time;
    uint topology;
    int invalidCluster;
    int invalidMode;
} pc;
void main() {
    uint id=gl_GlobalInvocationID.x;
    if(id>=pc.columns*pc.rows)return;
    uint cx=id%pc.columns,cy=id/pc.columns;
    for(uint y=0;y<9;y++)for(uint x=0;x<9;x++) {
        vec2 p=(vec2(cx,cy)+vec2(x,y)/8)/vec2(pc.columns,pc.rows)*8-4;
        float z=.55*sin(p.x*1.7+pc.time)*cos(p.y*1.3-pc.time*.7)+.2*sin(p.x*3+p.y*2+pc.time*1.3);
        pc.positions.data[id*81+y*9+x]=vec4(p.x,z,p.y,1);
    }
    for(uint y=0;y<8;y++)for(uint x=0;x<8;x++) {
        uint a=y*9+x,b=a+1,c=a+10,d=a+9,o=id*384+(y*8+x)*6;
        bool flip=((x+y+pc.topology)&1)!=0;
        pc.indices.data[o]=a;
        pc.indices.data[o+1]=flip?d:c;
        pc.indices.data[o+2]=b;
        pc.indices.data[o+3]=flip?b:a;
        pc.indices.data[o+4]=d;
        pc.indices.data[o+5]=c;
    }
    // A 9x9 vertex grid contains 8x8 quads: 81 vertices, 128 triangles, 384 indices.
    pc.descriptions.data[id]=Cluster(uvec4(id*81,id*384,81,128),uvec4(id,id,0,0));
    // Deliberate invalid address-range injection exercises the public builder's GPU guard.
    if(int(id)==pc.invalidCluster) {
        if(pc.invalidMode==1)pc.descriptions.data[id].range.x=0xffffffffu;
        if(pc.invalidMode==2)pc.indices.data[id*384]=100000u;
        if(pc.invalidMode==4)pc.positions.data[id*81].x=uintBitsToFloat(0x7fc00000u);
    }
}