export type ParsedMRZDates = {
  birthDate: string; // yyyy-mm-dd
  expiryDate: string; // yyyy-mm-dd
};

export type MRZScanResult = {
  documentNumber: string;
  expiryDate: string;
  birthDate: string;
};

export function normalizeDocumentNumber(docNumber: string): string {
  return docNumber.toUpperCase().replace(/O/g, "0");
}

function calculateCheckDigit(data: string): number {
  const weights = [7, 3, 1];
  const chars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ<";
  let sum = 0;

  for (let i = 0; i < data.length; i++) {
    const char = data[i];
    const value = chars.indexOf(char);
    if (value === -1) throw new Error(`Geçersiz karakter: ${char}`);
    sum += value * weights[i % 3];
  }

  return sum % 10;
}

function parseMRZDate(
  dateStr: string,
  checkDigit: string,
  referenceYear: number
): string {
  if (!/^\d{6}$/.test(dateStr) || !/^\d$/.test(checkDigit)) {
    throw new Error("Geçersiz tarih veya kontrol basamağı formatı.");
  }

  const calculated = calculateCheckDigit(dateStr);
  if (calculated !== parseInt(checkDigit, 10)) {
    throw new Error(`Kontrol basamağı hatalı (${dateStr} için).`);
  }

  const yy = parseInt(dateStr.slice(0, 2), 10);
  const mm = dateStr.slice(2, 4);
  const dd = dateStr.slice(4, 6);

  const century = Math.floor(referenceYear / 100) * 100;
  let fullYear = century + yy;
  if (fullYear > referenceYear + 10) {
    fullYear -= 100;
  }

  return `${fullYear}-${mm}-${dd}`;
}

export function normalizeMRZDates({
  birthDate,
  birthDateCheckDigit,
  expirationDate,
  expirationDateCheckDigit,
}: {
  birthDate: string;
  birthDateCheckDigit: string;
  expirationDate: string;
  expirationDateCheckDigit: string;
}): ParsedMRZDates {
  const currentYear = new Date().getFullYear();

  const expiryDate = parseMRZDate(
    expirationDate,
    expirationDateCheckDigit,
    currentYear + 10
  );
  const expiryYear = parseInt(expiryDate.slice(0, 4), 10);

  const _birthDate = parseMRZDate(
    birthDate,
    birthDateCheckDigit,
    expiryYear - 10
  );

  return {
    birthDate: _birthDate,
    expiryDate,
  };
}