/**
 * Thin runtime adapter around onnxruntime-{web,node}.
 *
 * Why an adapter
 * ──────────────
 * ``onnxruntime-web`` and ``onnxruntime-node`` ship with subtly
 * different ``InferenceSession.create`` signatures and execution
 * provider names (``'wasm'``/``'webgpu'`` vs ``'cpu'``/``'cuda'``).
 * Userland code shouldn't have to know which one is loaded — we pick
 * at runtime based on whether ``window`` exists, then re-export a
 * unified surface.
 *
 * Both packages are *peer dependencies* (``peerDependenciesMeta``
 * marks them optional) so users only install the one they need.
 */

import type * as OrtWeb from 'onnxruntime-web';
import type * as OrtNode from 'onnxruntime-node';

type OrtModule = typeof OrtWeb | typeof OrtNode;
type ExecutionProvider = 'webgpu' | 'wasm' | 'cpu' | 'cuda';

/** Re-exported ORT session interface, narrowed to what we use. */
export interface OrtSession {
  inputNames: readonly string[];
  outputNames: readonly string[];
  run(
    feeds: Record<string, OrtTensor>,
  ): Promise<Record<string, OrtTensor>>;
}

/** ORT tensor — matches both ``onnxruntime-web`` and
 * ``onnxruntime-node`` tensors at the structural level. */
export interface OrtTensor {
  type: string;
  data:
    | Float32Array
    | Int32Array
    | BigInt64Array
    | Uint8Array
    | Uint16Array;
  dims: readonly number[];
}

let _ort: OrtModule | null = null;

/**
 * Load whichever ORT package is installed. Browser prefers
 * ``onnxruntime-web``; Node prefers ``onnxruntime-node`` but will
 * accept ``-web`` as a fallback (slower but works).
 */
export async function loadOrt(): Promise<OrtModule> {
  if (_ort) return _ort;
  const isBrowser =
    typeof window !== 'undefined' && typeof document !== 'undefined';
  // Vite/webpack treat ``import('onnxruntime-web')`` as a static spec
  // and bundle the module if it's a real dep; with peer-deps it stays
  // dynamic and only loads when present. ``catch`` swallows the
  // missing-peer-dep case and falls back to the alternate runtime.
  if (isBrowser) {
    try {
      _ort = (await import('onnxruntime-web')) as unknown as OrtModule;
      return _ort;
    } catch {
      throw new Error(
        '@cp500/infon-coref: onnxruntime-web is required in the ' +
          'browser. Install with: npm install onnxruntime-web',
      );
    }
  }
  // Node.
  try {
    _ort = (await import('onnxruntime-node')) as unknown as OrtModule;
    return _ort;
  } catch {
    try {
      _ort = (await import('onnxruntime-web')) as unknown as OrtModule;
      return _ort;
    } catch {
      throw new Error(
        '@cp500/infon-coref: onnxruntime-node (preferred) or ' +
          'onnxruntime-web is required. Install with: ' +
          'npm install onnxruntime-node',
      );
    }
  }
}

/** Resolve ``'auto'`` to a concrete EP for the current runtime. */
async function resolveProvider(
  device: 'auto' | ExecutionProvider,
  ort: OrtModule,
): Promise<ExecutionProvider> {
  const isBrowser =
    typeof window !== 'undefined' && typeof document !== 'undefined';
  if (device !== 'auto') return device;
  if (isBrowser) {
    // Probe WebGPU. Even when the API exists, the device may be
    // unreachable (older Macbooks, Firefox without flags, etc.).
    if (typeof (navigator as { gpu?: unknown }).gpu !== 'undefined') {
      try {
        const adapter = await (
          navigator as { gpu?: { requestAdapter(): Promise<unknown> } }
        ).gpu!.requestAdapter();
        if (adapter) return 'webgpu';
      } catch {
        /* fall through */
      }
    }
    return 'wasm';
  }
  // Node: default CPU (CUDA needs explicit opt-in via ``device: 'cuda'``).
  return 'cpu';
}

/** Helper: create an ONNX inference session with sane defaults. */
export async function createSession(
  modelPath: string | ArrayBuffer | Uint8Array,
  device: 'auto' | ExecutionProvider = 'auto',
): Promise<OrtSession> {
  const ort = await loadOrt();
  const provider = await resolveProvider(device, ort);
  const session = await ort.InferenceSession.create(modelPath as never, {
    executionProviders: [provider],
    graphOptimizationLevel: 'all',
  });
  return session as unknown as OrtSession;
}

/** Helper: build an ORT tensor from a typed array.
 *
 * The web/node packages share a constructor signature but TypeScript
 * doesn't see it because we don't statically import them. */
export async function makeTensor(
  type: 'float32' | 'int64' | 'float16',
  data:
    | Float32Array
    | BigInt64Array
    | Uint16Array,
  dims: readonly number[],
): Promise<OrtTensor> {
  const ort = await loadOrt();
  // ``Tensor`` constructor: new ort.Tensor(type, data, dims).
  return new (ort as unknown as { Tensor: new (...args: unknown[]) => OrtTensor })
    .Tensor(type, data, dims as number[]);
}