/**
 * The GPU device, requested the same way in the page and the CLI.
 *
 * The precompute holds its whole kernel bank in one storage buffer, which
 * at fine grids outgrows WebGPU's 128 MiB default binding size, so the
 * request asks for the adapter's actual maximum buffer and binding sizes.
 * That is a capacity request: if the adapter cannot give more, the request
 * still succeeds and a too-large bake fails with a clear buffer error.
 */
let heldAdapter: GPUAdapter | null = null;

export async function requestDevice(): Promise<GPUDevice> {
  if (!navigator.gpu) {
    throw new Error(
      'this environment has no WebGPU. In the browser: Chrome and Edge 113+, ' +
        'Safari 26+; on Linux it may need enabling explicitly. In node: the ' +
        'optional `webgpu` package (Google Dawn).',
    );
  }
  const adapter = await navigator.gpu.requestAdapter({ powerPreference: 'high-performance' });
  if (!adapter) throw new Error('WebGPU found no adapter on this machine.');
  heldAdapter = adapter;
  return adapter.requestDevice({
    requiredLimits: {
      maxBufferSize: adapter.limits.maxBufferSize,
      maxStorageBufferBindingSize: adapter.limits.maxStorageBufferBindingSize,
    },
  });
}

export const currentAdapter = (): GPUAdapter | null => heldAdapter;