'use strict';

const encoding = require ('@sapphirecode/encoding-helper');
const { hash_sha512 } = require ('./hashing');
const { asym_sign, asym_verify } = require ('./rsa');

/**
 * sign an object
 *
 * @param {any} obj object to sign
 * @param {string} key key to use
 * @param {string|Object} key_info key identifier
 * @returns {string} signed object
 */
function sign_object (obj, key, key_info = null) {
  const payload = {
    iat: Date.now (),
    obj,
    ...(typeof key_info === 'object' ? key_info : { key_info })
  };
  const str = encoding.to_b58 (JSON.stringify (payload));
  const is_rsa = (/^-----BEGIN PRIVATE KEY-----/u).test (key);
  const signature = is_rsa ? asym_sign (str, key) : hash_sha512 (str, key);
  const token = encoding.to_b58 (signature, 'hex');
  const res = `${str}.${token}.2`;
  return res;
}

/**
 * parse a string signature
 *
 * @param {string} str string to verify
 * @param {string|((Object)=>string|Promise<string>)|null} key used key
 * @returns {Promise<any>} returns object if successful, else null
 */
async function parse_signature (str, key = null) {
  let dec = str.split ('.');
  const version = dec[2];
  const res = {};
  switch (version) {
    case '2':
      res.json = JSON.parse (encoding.to_utf8 (dec[0], 'base58'));
      res.token = encoding.to_hex (dec[1], 'base58');
      break;
    default:
      dec = decodeURIComponent (str)
        .split ('.');
      res.json = JSON.parse (
        encoding.to_utf8 (dec[0], 'base64')
      );
      res.token = encoding.to_hex (dec[1], 'base64');
      break;
  }

  if (key !== null) {
    const string_key = typeof key === 'string' ? key : await key (res.json);
    res.is_rsa = (/^-----BEGIN RSA PUBLIC KEY-----/u).test (string_key);
    res.hash = res.is_rsa
      ? asym_verify (dec[0], string_key, res.token)
      : hash_sha512 (dec[0], string_key);
  }
  return res;
}

/**
 * verify a signed object and return its info and contents
 *
 * @param {string} str string to verify
 * @param {string|((Object)=>string|Promise<string>)} key used key
 * @param {number|((Object)=>number|Promise<number>)} timeout timeout (optional)
 * @returns {Promise<any>} returns object if successful, else null
 */
async function verify_signature_get_info (str, key, timeout = 0) {
  if (typeof str !== 'string')
    return null;
  const { json, token, hash, is_rsa } = await parse_signature (str, key);
  if (is_rsa ? !hash : (token !== hash))
    return null;
  const time = Date.now () - json.iat;
  const num_timeout = typeof timeout === 'number'
    ? timeout
    : await timeout (json);
  if (num_timeout === 0 || time <= num_timeout)
    return json;
  return null;
}

/**
 * verify a signed object and return its contents
 *
 * @param {string} str string to verify
 * @param {string|((Object)=>string|Promise<string>)} key used key
 * @param {number|((Object)=>number|Promise<number>)} timeout timeout (optional)
 * @returns {Promise<any>} returns object if successful, else null
 */
async function verify_signature (str, key, timeout = 0) {
  const res = await verify_signature_get_info (str, key, timeout);
  if (res === null)
    return null;
  return res.obj;
}

/**
 * get a signed object info and data
 *
 * @param {string} str string to decode
 * @returns {Promise<any>} data
 */
async function get_signature_info (str) {
  if (typeof str !== 'string')
    return null;
  const { json } = await parse_signature (str);
  return json;
}

/**
 * decode a signed object without verifying the signature
 *
 * @param {string} str string to decode
 * @returns {Promise<any>} object
 */
async function decode_signed (str) {
  const info = await get_signature_info (str);
  if (info)
    return info.obj;
  return null;
}

module.exports = {
  decode_signed,
  get_signature_info,
  sign_object,
  verify_signature,
  verify_signature_get_info
};