<?php

declare(strict_types = 1);

namespace Systopia\PipelineTest;

final class IbanValidator {

  private const LENGTHS = [
    'AT' => 20,
    'BE' => 16,
    'CH' => 21,
    'DE' => 22,
    'ES' => 24,
    'FR' => 27,
    'IT' => 27,
    'LU' => 20,
    'NL' => 18,
  ];

  public function isValid(string $iban): bool {
    $normalized = $this->normalize($iban);

    if (1 !== preg_match('/^[A-Z]{2}[0-9]{2}[A-Z0-9]+$/', $normalized)) {
      return FALSE;
    }

    if (strlen($normalized) !== (self::LENGTHS[substr($normalized, 0, 2)] ?? NULL)) {
      return FALSE;
    }

    return 1 === $this->mod97(substr($normalized, 4) . substr($normalized, 0, 4));
  }

  public function normalize(string $iban): string {
    return strtoupper(str_replace([' ', '-'], '', $iban));
  }

  private function mod97(string $rearranged): int {
    $remainder = 0;
    foreach (str_split($rearranged) as $character) {
      $digits = ctype_digit($character) ? $character : (string) (ord($character) - 55);
      foreach (str_split($digits) as $digit) {
        $remainder = ($remainder * 10 + (int) $digit) % 97;
      }
    }

    return $remainder;
  }

}