/**
 * Desktop WebGPU for the command-line scripts, via the optional `webgpu`
 * package (prebuilt Google Dawn). Installs Dawn under the globals the
 * host code expects (navigator.gpu, GPUBufferUsage, ...) so everything
 * under src/ runs here unchanged.
 */
export const errMsg = (e: unknown): string =>
  e instanceof Error ? e.message : String(e);

export async function installWebGpu(): Promise<string> {
  const specifier = 'webgpu';
  let mod: { create: (flags: string[]) => GPU; globals: Record<string, unknown> };
  try {
    mod = await import(specifier);
  } catch (e) {
    const detail = errMsg(e);
    if (/Cannot find (package|module) '?webgpu'?/.test(detail)) {
      throw new Error(
        'desktop WebGPU needs the optional `webgpu` package (prebuilt Google Dawn):\n' +
          '  npm install webgpu',
      );
    }
    throw new Error(`the \`webgpu\` package is installed but did not load:\n  ${detail}`);
  }
  Object.assign(globalThis, mod.globals);
  const dawnFlags = process.env.DAWN_FLAGS?.split(';').filter(Boolean) ?? [];
  Object.defineProperty(globalThis, 'navigator', {
    value: { gpu: mod.create(dawnFlags) },
    configurable: true,
    writable: true,
  });
  const { version } = await import(`${specifier}/package.json`, {
    with: { type: 'json' },
  }).then(
    (m) => m.default as { version: string },
    () => ({ version: '?' }),
  );
  return `node-webgpu ${version} (Google Dawn)`;
}