Add IBAN validator with QA workflows

src/IbanValidator.php

@@ -0,0 +1,51 @@
+<?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;
+  }
+
+}