import base58_to_binary from "base58-js/base58_to_binary.js";
import recover_public from "isomorphic-secp256k1-js/recover_public_key.js";

import public_key_to_wif from "./keys/public_key_to_wif.js";

type recover_public_key_args = {
  signature: string; // hex string
  hash: string | Uint8Array;
};

/**
 * Recovers an Antelope secp256k1 public key from K1 signature.
 */
export default async function recover_public_key({
  signature,
  hash,
}: recover_public_key_args): Promise<string> {
  let hash_array: Uint8Array;

  // Handle the case where hash is a string
  if (typeof hash === "string") {
    const hashMatches = hash.match(/[a-fA-F0-9]{2}/gmu);

    if (hashMatches) {
      hash_array = Uint8Array.from(hashMatches.map((i) => Number(`0x${i}`)));
    } else {
      throw new Error("Invalid hash format.");
    }
  }
  // Handle the case where hash is already a Uint8Array
  else if (hash instanceof Uint8Array) {
    hash_array = hash;
  }
  // Throw an error if hash is neither a string nor Uint8Array
  else {
    throw new Error("Hash must be a string or a Uint8Array.");
  }

  if (!signature?.startsWith("SIG_K1_"))
    throw new TypeError("Signature must start with “SIG_K1_”");

  const raw_sig = base58_to_binary(signature.replace("SIG_K1_", "")).slice(
    0,
    -4
  );

  const v = raw_sig.slice(0, 1)[0] - 31;
  const r = raw_sig.slice(1, 33);
  const s = raw_sig.slice(33, 65);

  return public_key_to_wif(
    await recover_public({ hash: hash_array, signature: { r, s, v } })
  );
}