struct Output
{
    float4 Color : TEXCOORD0;
    float2 UV : TEXCOORD1;
    float4 Position : SV_Position;
};

#include "RootConstants.hlsl"

struct Vertex
{
    float2 Pos;
    float2 UV;
    uint   Color;
};

Output main(uint vertexIndex : SV_VertexID)
{
    Output output;

    // Retrieve the vertex buffer using SM6.6 bindless syntax
    ByteAddressBuffer buffer = ResourceDescriptorHeap[BufferIndex];

    // Add VertexOffset for indexed drawing with bindless buffers
    // (SV_VertexID in indexed draw is raw index from index buffer, doesn't include BaseVertexLocation)
    uint actualVertexIndex = vertexIndex + VertexOffset;

    // ImDrawVert stride = 20 bytes (Vec2 pos + Vec2 uv + uint color)
    uint stride = 20;
    uint offset = actualVertexIndex * stride;

    float2 pos = asfloat(buffer.Load2(offset));
    float2 uv  = asfloat(buffer.Load2(offset + 8));
    uint col   = buffer.Load(offset + 16);

    // Unpack color (uint to float4)
    // ImGui colors are 0xAABBGGRR (ABGR packed)
    // We need to unpack to float4.
    // HLSL unpacks as little endian.
    // uint 0xAABBGGRR -> byte0=RR, byte1=GG, byte2=BB, byte3=AA
    float4 c;
    c.x = float(col & 0xFF) / 255.0f;
    c.y = float((col >> 8) & 0xFF) / 255.0f;
    c.z = float((col >> 16) & 0xFF) / 255.0f;
    c.w = float((col >> 24) & 0xFF) / 255.0f;

    // Transform
    // ImGui sends pixel coordinates.
    // We need to transform to NDC [-1, 1].
    // PushConstants should contain Scale and Translate.
    // float2 Scale = 2.0 / DisplaySize
    // float2 Translate = -1.0 - (DisplayPos * Scale)
    
    // We will assume PushConstants are float2 Scale, float2 Translate.
    // Struct in RootConstants.hlsl?
    // RootConstants.hlsl likely defines `cbuffer PushConstants : register(b0)`.
    // Let's assume standard push constants usage.
    // Debug.vert.hlsl used `ViewProjection`. 
    // We need to customize PushConstants or reuse `ViewProjection` slot?
    // Juliet uses 128 bytes of push constants.
    // We can map float4 ProjectionMatrix (or similar).
    
    // Use Scale and Translate from RootConstants
    output.Position = float4(pos * Scale + Translate, 0.0f, 1.0f);
    output.Color = c;
    output.UV = uv;
    
    return output;
}