const hash = keccak256(toUtf8Bytes("https://example.org/story"));

{
  "algorithm": "sha256",
  "value": "0x..."
}

async function verifyArtifact(url: string, expected: string) {
  const res = await fetch(url);
  if (!res.ok) return { state: "unavailable" as const };

  const bytes = await res.arrayBuffer();
  const digest = await crypto.subtle.digest("SHA-256", bytes);
  const actual = "0x" + Array.from(new Uint8Array(digest), b => b.toString(16).padStart(2, "0")).join("");

  return actual.toLowerCase() === expected.toLowerCase()
    ? { state: "verified" as const, actual }
    : { state: "mismatch" as const, actual };
}