worker.js

async function work({ challenge, difficulty, startAt }) {
  const { default: initWasm, proof_of_work } = await import('./brain_pow.js')
  const wasmUrl = new URL('./brain_pow_bg.wasm', import.meta.url)
  await initWasm({ module_or_path: wasmUrl })
  const result = proof_of_work(challenge, difficulty, startAt)
  return result
}

globalThis.onmessage = (e) => {
  const { challenge, difficulty, startAt } = e.data
  work({ challenge, difficulty, startAt })
    .then((result) => {
      globalThis.postMessage({ result })
      globalThis.close()
    })
    .catch((error) => {
      if (typeof error === 'string') {
        globalThis.postMessage({ error })
      } else {
        globalThis.postMessage({ error: error.message })
      }
      globalThis.close()
    })
}

globalThis.postMessage({ ready: true })