import base58_to_binary from "base58-js/base58_to_binary";
import ripemd160 from "ripemd160-js/ripemd160.js";

/**
 * Serialises an EOS signature to WASM hex string.
 * @name signature
 * @kind function
 * @param {string} sig_string EOS signature to be serilaised.
 * @returns {string} Hex string.
 * @ignore
 */
async function signature(sig_string) {
  if (!sig_string.startsWith("SIG_K1_"))
    throw new Error("Invalid signature format, must start with “SIG_K1_”");

  const signature_as_bin = base58_to_binary(sig_string.replace("SIG_K1_", ""));
  const K1 = [75, 49]; // K1 as ascii
  const raw_sig = signature_as_bin.slice(0, -4);
  const hash = await ripemd160(new Uint8Array([...raw_sig, ...K1]));

  hash.slice(0, 4).forEach((x, i) => {
    if (x != signature_as_bin.slice(-4)[i])
      throw new Error("Invalid signature checksum.");
  });

  const key_type = {
    k1: "00",
    r1: "01",
    wa: "02",
  };

  return raw_sig.reduce(
    (acc, i) => (acc += i.toString(16).padStart(2, "00")),
    key_type.k1
  );
}

export default signature;