#pragma kernel UpdateParticleStrip

#pragma only_renderers d3d11 playstation xboxone xboxseries vulkan metal switch glcore gles3 webgpu

#include "HLSLSupport.cginc"

#define NB_THREADS_PER_GROUP 64
#define VFX_USE_INSTANCING 1
#define VFX_INSTANCING_BATCH_INDIRECTION 1
#define VFX_INSTANCING_FIXED_SIZE stripCount
#define STRIP_COUNT stripCount

CBUFFER_START(params)
    uint dispatchWidth;
    uint stripCount;
    uint particlePerStripCount;
    float4 instancingConstants;
CBUFFER_END

#include "VFXInstancing.hlsl"

RWStructuredBuffer<uint> stripDataBuffer;

#include "Packages/com.unity.visualeffectgraph/Shaders/VFXParticleStripCommon.hlsl"

[numthreads(NB_THREADS_PER_GROUP,1,1)]
void UpdateParticleStrip(uint3 groupId          : SV_GroupID,
                         uint3 groupThreadId    : SV_GroupThreadID)
{
    uint index = groupThreadId.x + groupId.x * NB_THREADS_PER_GROUP + groupId.y * dispatchWidth * NB_THREADS_PER_GROUP;

    if (index < stripCount * (uint)instancingActiveCount)
    {
        uint instanceIndex, instanceActiveIndex, instanceCurrentIndex;
        uint stripIndex = VFXInitInstancing(index, instanceIndex, instanceActiveIndex, instanceCurrentIndex);
        uint bufferIndex = STRIP_DATA_INDEX(instanceIndex, stripIndex);

        bool isEmpty = (STRIP_DATA(STRIP_MIN_ALIVE, bufferIndex) & ~1) == ~1;
        uint particleCount = isEmpty ? 0 : STRIP_DATA(STRIP_MAX_ALIVE, bufferIndex) - STRIP_DATA(STRIP_MIN_ALIVE, bufferIndex) + 1;
        STRIP_DATA(STRIP_FIRST_INDEX, bufferIndex) = isEmpty ? 0 : (STRIP_DATA(STRIP_FIRST_INDEX, bufferIndex) + STRIP_DATA(STRIP_MIN_ALIVE, bufferIndex)) % particlePerStripCount;
        STRIP_DATA(STRIP_NEXT_INDEX, bufferIndex) = particleCount;
        STRIP_DATA(STRIP_PREV_NEXT_INDEX, bufferIndex) = particleCount; // Store particle count twice so that it can be read consistenly in next Init (as next index will be atomically incremented in init)
        STRIP_DATA(STRIP_MIN_ALIVE, bufferIndex) = isEmpty ? ~1 : ~0;
        STRIP_DATA(STRIP_MAX_ALIVE, bufferIndex) = 0;

        InterlockedAdd(STRIP_PARTICLE_COUNTER(instanceIndex), particleCount);
    }
}