/**
 * Lazy, guarded loader for wasm-vips (libvips compiled to WASM — the same engine
 * as `sharp`). It's used as a progressive enhancement for high-quality (lanczos3)
 * downscaling. Initialization is attempted once; on any failure — or in browsers
 * without cross-origin isolation / SharedArrayBuffer — we resolve to null and the
 * caller falls back to the canvas resampler.
 */

// wasm-vips ships rich types, but we treat it loosely at this dynamic boundary.
type Vips = any;

let vipsPromise: Promise<Vips | null> | null = null;

function withTimeout<T>(promise: Promise<T>, ms: number, label: string): Promise<T> {
  return new Promise<T>((resolve, reject) => {
    const timer = setTimeout(() => reject(new Error(`${label} timed out after ${ms}ms`)), ms);
    promise.then(
      (value) => {
        clearTimeout(timer);
        resolve(value);
      },
      (err) => {
        clearTimeout(timer);
        reject(err);
      },
    );
  });
}

export function loadVips(): Promise<Vips | null> {
  if (vipsPromise) return vipsPromise;
  vipsPromise = (async () => {
    try {
      const mod: any = await import("wasm-vips");
      const factory = (mod.default ?? mod) as (opts?: unknown) => Promise<Vips>;
      // dynamicLibraries: [] skips the optional HEIF/JXL/SVG modules we don't need.
      const vips = await withTimeout(factory({ dynamicLibraries: [] }), 20_000, "wasm-vips init");
      return vips ?? null;
    } catch (err) {
      console.warn("[wimp] wasm-vips unavailable — falling back to the canvas engine.", err);
      return null;
    }
  })();
  return vipsPromise;
}