export function hexToBytes(hex: string): Uint8Array {
  const bytes = new Uint8Array(hex.length / 2);
  for (let i = 0; i < bytes.length; i++) {
    bytes[i] = Number.parseInt(hex.substring(i * 2, i * 2 + 2), 16);
  }
  return bytes;
}

export function bytesToHex(bytes: Uint8Array): string {
  return Array.from(bytes)
    .map((b) => b.toString(16).padStart(2, "0"))
    .join("");
}

export async function hmacHex(data: string, secret: string): Promise<string> {
  const key = await crypto.subtle.importKey(
    "raw",
    new TextEncoder().encode(secret),
    { name: "HMAC", hash: "SHA-256" },
    false,
    ["sign"],
  );
  const signature = await crypto.subtle.sign("HMAC", key, new TextEncoder().encode(data));
  return bytesToHex(new Uint8Array(signature));
}

// crypto.subtle.timingSafeEqual throws on mismatched-length inputs rather
// than returning false, so length is checked explicitly first.
export function timingSafeEqualHex(a: string, b: string): boolean {
  if (a.length !== b.length) return false;
  return crypto.subtle.timingSafeEqual(hexToBytes(a), hexToBytes(b));
}