export function isValidNationalCode(code: string): boolean {
  if (!/^\d{10}$/.test(code)) {
    return false;
  }

  if (/^(\d)\1{9}$/.test(code)) {
    return false;
  }

  const check = parseInt(code[9], 10);
  let sum = 0;

  for (let i = 0; i < 9; i++) {
    sum += parseInt(code[i], 10) * (10 - i);
  }

  const remainder = sum % 11;
  return remainder < 2 ? check === remainder : check === 11 - remainder;
}