#version 450

layout(set = 3, binding = 0) readonly buffer FaceBuffer {
    uint faces[];
};

layout(push_constant) uniform matrices {
    vec4 ModelOffset;
    vec4 Padding0;
    vec4 Padding1;
    vec4 Padding2;
    uint materialIdx;
} push_constants;

layout(location = 0) out vec2 outTextCoord;
layout(location = 1) out flat uint outMaterialIdx;

const uint TRI_TO_CORNER[6] = uint[6](0u, 1u, 2u, 0u, 2u, 3u);

vec3 buildFaceCornerPosition(uvec3 voxelPos, uint faceId, uint cornerIndex) {
    vec3 p = vec3(voxelPos);

    if (faceId == 0u) {
        if (cornerIndex == 0u) return p + vec3(0.0, 1.0, 0.0);
        if (cornerIndex == 1u) return p + vec3(0.0, 1.0, 1.0);
        if (cornerIndex == 2u) return p + vec3(1.0, 1.0, 1.0);
        return p + vec3(1.0, 1.0, 0.0);
    }

    if (faceId == 1u) {
        if (cornerIndex == 0u) return p + vec3(0.0, 0.0, 0.0);
        if (cornerIndex == 1u) return p + vec3(1.0, 0.0, 0.0);
        if (cornerIndex == 2u) return p + vec3(1.0, 0.0, 1.0);
        return p + vec3(0.0, 0.0, 1.0);
    }

    if (faceId == 2u) {
        if (cornerIndex == 0u) return p + vec3(1.0, 0.0, 0.0);
        if (cornerIndex == 1u) return p + vec3(1.0, 1.0, 0.0);
        if (cornerIndex == 2u) return p + vec3(1.0, 1.0, 1.0);
        return p + vec3(1.0, 0.0, 1.0);
    }

    if (faceId == 3u) {
        if (cornerIndex == 0u) return p + vec3(0.0, 0.0, 0.0);
        if (cornerIndex == 1u) return p + vec3(0.0, 0.0, 1.0);
        if (cornerIndex == 2u) return p + vec3(0.0, 1.0, 1.0);
        return p + vec3(0.0, 1.0, 0.0);
    }

    if (faceId == 4u) {
        if (cornerIndex == 0u) return p + vec3(0.0, 0.0, 1.0);
        if (cornerIndex == 1u) return p + vec3(1.0, 0.0, 1.0);
        if (cornerIndex == 2u) return p + vec3(1.0, 1.0, 1.0);
        return p + vec3(0.0, 1.0, 1.0);
    }

    if (cornerIndex == 0u) return p + vec3(0.0, 0.0, 0.0);
    if (cornerIndex == 1u) return p + vec3(0.0, 1.0, 0.0);
    if (cornerIndex == 2u) return p + vec3(1.0, 1.0, 0.0);
    return p + vec3(1.0, 0.0, 0.0);
}

void main() {
    uint faceRecordIndex = uint(gl_VertexIndex) / 6u;
    uint triangleVertex = uint(gl_VertexIndex) % 6u;
    uint cornerIndex = TRI_TO_CORNER[triangleVertex];

    uint packedFace = faces[faceRecordIndex];

    uint voxelX =  packedFace         & 0x1Fu;
    uint voxelY = (packedFace >> 5u)  & 0x1Fu;
    uint voxelZ = (packedFace >> 10u) & 0x1Fu;
    uint faceId = (packedFace >> 15u) & 0x7u;
    uint matId  = (packedFace >> 18u) & 0xFFu;

    vec3 localPos = buildFaceCornerPosition(uvec3(voxelX, voxelY, voxelZ), faceId, cornerIndex);
    vec3 worldPos = localPos + push_constants.ModelOffset.xyz * 16.0;

    outTextCoord = vec2(0.0);
    outMaterialIdx = matId;

    gl_Position = vec4(worldPos, 1.0);
}