#version 430 core
// Campaign V slice V6c — the Vulkan RHI verification shader.
//
// Plan §4.11 asks the active capability probe to "build one real pipeline from
// the committed .spv and render an offscreen triangle sampling a table slot",
// and slice V5 recorded that as its one deliberate deviation because the .spv
// toolchain did not exist yet. This is that shader, and it does rather more: it
// is what the V6 backend draws its verification scene with, so one pipeline
// exercises the vertex layout, both storage bindings, the shared push-constant
// block, gl_DrawID under multi-draw-indirect, and the set-2 texture table.
//
// VULKAN-DIALECT ONLY. Unlike the eight production pairs this is not compiled by
// the GL backend: it reads the push-constant block and the descriptor array that
// tools/compile-shaders.ps1 injects, neither of which GL has. It is not a fork of
// anything — no GL renderer draws with it — and it retires when the ported world
// renderers become the backend's own proof.

layout(location = 0) in vec3 aPosition;
layout(location = 1) in vec3 aNormal;
layout(location = 2) in vec2 aTexCoord;

// set 0 binding 0 — per-instance transforms, exactly as GpuBindingModel pins it.
struct InstanceData {
    mat4 transform;
};
layout(std430, binding = 0) readonly buffer InstanceBuffer {
    InstanceData Instances[];
};

// set 0 binding 1 — per-draw batch metadata at the pinned 16-byte std430 stride.
// The first word is the texture-table slot: since slice V2 a batch carries an
// index, not a 64-bit bindless handle, which is what makes this data model
// backend-neutral.
struct BatchData {
    uint textureIndex;
    uint textureLayer;
    uint tint;
    uint pad;
};
layout(std430, binding = 1) readonly buffer BatchBuffer {
    BatchData Batches[];
};

layout(location = 0) out vec3 vNormal;
layout(location = 1) out vec2 vTexCoord;
layout(location = 2) out flat uint vTextureIndex;
layout(location = 3) out flat uint vTextureLayer;
layout(location = 4) out flat uint vTint;

void main() {
    // gl_BaseInstanceARB + gl_InstanceID is the GL idiom mesh_modern uses; the
    // injected preamble maps it onto Vulkan's gl_InstanceIndex, which already
    // includes firstInstance.
    int instanceIndex = gl_BaseInstanceARB + gl_InstanceID;
    mat4 model = Instances[instanceIndex].transform;

    // gl_DrawID resets to 0 at the start of each indirect dispatch on both APIs,
    // so a pass beginning partway into the batch array offsets its lookup —
    // issue #52's uDrawIDOffset pattern, carried over unchanged.
    BatchData b = Batches[uDrawIDOffset + gl_DrawIDARB];
    vTextureIndex = b.textureIndex;
    vTextureLayer = b.textureLayer;
    vTint = b.tint;

    vec4 world = model * vec4(aPosition, 1.0);
    gl_Position = uViewProjection * world;
    vNormal = mat3(model) * aNormal;
    vTexCoord = aTexCoord;
}