/* ============================================================================
 * hash-worker.js — SHA-256 of a file already saved in OPFS, off the main
 * thread, read in 4 MiB slices (never the whole video in memory).
 *
 * In:  { name }                 file name under OPFS videos/ (e.g. "abc.mp4")
^ * Out: { ok: true, sha256, size, engine } | { ok: false, error }
 * ========================================================================== */
'use strict';
importScripts('/sha256.js');

self.onmessage = async (e) => {
  const { name } = e.data || {};
  try {
    const root = await navigator.storage.getDirectory();
    const dir = await root.getDirectoryHandle('videos');
    const file = await (await dir.getFileHandle(String(name))).getFile();
    const h = self.Sha256.create();
    const STEP = 4 * 1024 * 1024;
    for (let pos = 0; pos < file.size; pos += STEP) {
      h.update(new Uint8Array(await file.slice(pos, pos + STEP).arrayBuffer()));
    }
    self.postMessage({ ok: true, sha256: h.hex(), size: file.size, engine: self.Sha256.engine() });
  } catch (err) {
    self.postMessage({ ok: false, error: err && err.message ? err.message : String(err) });
  }
};