"use strict";

const crypto = require("crypto");
const { promisify } = require("util");

const scryptAsync = promisify(crypto.scrypt);

const KEY_LEN = 64;
const SALT_LEN = 16;
const SCRYPT_OPTIONS = {
  N: 16384,
  r: 8,
  p: 1,
  maxmem: 32 * 1024 * 1024,
};

/**
 * Хеширует пароль с помощью scrypt и случайной соли.
 * @param {string} password
 * @returns {Promise<string>} Формат: "saltHex:derivedKeyHex"
 */
async function hashPassword(password) {
  if (typeof password !== "string") {
    throw new TypeError("Пароль должен быть строкой");
  }
  const salt = crypto.randomBytes(SALT_LEN);
  const derivedKey = await scryptAsync(password, salt, KEY_LEN, SCRYPT_OPTIONS);
  return `${salt.toString("hex")}:${derivedKey.toString("hex")}`;
}

/**
 * Синхронное хеширование (для инициализации при старте).
 * @param {string} password
 * @returns {string}
 */
function hashPasswordSync(password) {
  if (typeof password !== "string") {
    throw new TypeError("Пароль должен быть строкой");
  }
  const salt = crypto.randomBytes(SALT_LEN);
  const derivedKey = crypto.scryptSync(password, salt, KEY_LEN, SCRYPT_OPTIONS);
  return `${salt.toString("hex")}:${derivedKey.toString("hex")}`;
}

/**
 * Проверяет пароль против сохранённого scrypt-хеша с защитой от тайминг-атак.
 * @param {string} password
 * @param {string} storedHash
 * @returns {Promise<boolean>}
 */
async function verifyPassword(password, storedHash) {
  if (typeof password !== "string" || typeof storedHash !== "string") {
    return false;
  }

  const parts = storedHash.split(":");
  if (parts.length !== 2) {
    return false;
  }

  const [saltHex, keyHex] = parts;
  try {
    const salt = Buffer.from(saltHex, "hex");
    const originalKey = Buffer.from(keyHex, "hex");

    if (salt.length !== SALT_LEN || originalKey.length !== KEY_LEN) {
      return false;
    }

    const derivedKey = await scryptAsync(password, salt, KEY_LEN, SCRYPT_OPTIONS);
    return crypto.timingSafeEqual(originalKey, derivedKey);
  } catch {
    return false;
  }
}

/**
 * Синхронная проверка пароля.
 * @param {string} password
 * @param {string} storedHash
 * @returns {boolean}
 */
function verifyPasswordSync(password, storedHash) {
  if (typeof password !== "string" || typeof storedHash !== "string") {
    return false;
  }

  const parts = storedHash.split(":");
  if (parts.length !== 2) {
    return false;
  }

  const [saltHex, keyHex] = parts;
  try {
    const salt = Buffer.from(saltHex, "hex");
    const originalKey = Buffer.from(keyHex, "hex");

    if (salt.length !== SALT_LEN || originalKey.length !== KEY_LEN) {
      return false;
    }

    const derivedKey = crypto.scryptSync(password, salt, KEY_LEN, SCRYPT_OPTIONS);
    return crypto.timingSafeEqual(originalKey, derivedKey);
  } catch {
    return false;
  }
}

module.exports = {
  hashPassword,
  hashPasswordSync,
  verifyPassword,
  verifyPasswordSync,
};