export const DIRECTOR_MAX_GLB_BYTES = 25 * 1024 * 1024;
/** Only self-contained GLB 2.0 files are accepted; external buffers/textures are not portable. */
export function validateDirectorGlb(buffer: ArrayBuffer) {
  if (buffer.byteLength < 20 || buffer.byteLength > DIRECTOR_MAX_GLB_BYTES)
    throw new Error("请上传 25 MiB 以内的有效 GLB 模型");
  const view = new DataView(buffer);
  if (
    view.getUint32(0, true) !== 0x46546c67 ||
    view.getUint32(4, true) !== 2 ||
    view.getUint32(8, true) !== buffer.byteLength
  )
    throw new Error("文件不是有效的 GLB 2.0 模型");
  const length = view.getUint32(12, true);
  if (
    view.getUint32(16, true) !== 0x4e4f534a ||
    length % 4 ||
    length > buffer.byteLength - 20
  )
    throw new Error("GLB 场景数据不完整");
  let document: any;
  try {
    document = JSON.parse(
      new TextDecoder().decode(new Uint8Array(buffer, 20, length)),
    );
  } catch {
    throw new Error("GLB 场景数据无效");
  }
  if (
    document?.asset?.version !== "2.0" ||
    !Array.isArray(document.meshes) ||
    !document.meshes.length
  )
    throw new Error("GLB 中没有可显示的网格");
  for (const resource of [
    ...(document.buffers || []),
    ...(document.images || []),
  ]) {
    if (resource.uri && !/^data:/i.test(resource.uri))
      throw new Error("请将纹理和缓冲区嵌入 GLB 后重新上传");
  }
  return document;
}