Refactor IBAN checksum to calculator class, Add unit tests

src/Faker/Calculator/Iban.php

@@ -0,0 +1,67 @@
+<?php
+
+namespace Faker\Calculator;
+
+class Iban
+{
+    /**
+     * Generates IBAN Checksum
+     *
+     * @param string $iban
+     * @return string Checksum (numeric string)
+     */
+    public static function checksum($iban)
+    {
+        // Move first four digits to end and set checksum to '00'
+        $checkString = substr($iban, 4) . substr($iban, 0, 2) . '00';
+
+        // Replace all letters with their number equivalents
+        $checkString = preg_replace_callback('/[A-Z]/', array('self','alphaToNumberCallback'), $checkString);
+
+        // Perform mod 97 and subtract from 98
+        $checksum = 98 - self::mod97($checkString);
+
+        return str_pad($checksum, 2, '0', STR_PAD_LEFT);
+    }
+
+    private static function alphaToNumberCallback($match)
+    {
+        return self::alphaToNumber($match[0]);
+    }
+
+    /**
+     * Converts letter to number
+     *
+     * @param string $char
+     * @return int
+     */
+    public static function alphaToNumber($char)
+    {
+        return ord($char) - 55;
+    }
+
+    /**
+     * Calculates mod97 on a numeric string
+     *
+     * @param string $number Numeric string
+     * @param int
+     */
+    public static function mod97($number)
+    {
+        $checksum = (int)$number[0];
+        for ($i = 1, $size = strlen($number); $i < $size; $i++) {
+            $checksum = (10 * $checksum + (int) $number[$i]) % 97;
+        }
+        return $checksum;
+    }
+
+    /**
+     * Checks whether an IBAN has a valid checksum
+     *
+     * @return boolean
+     */
+    public static function isValid($iban)
+    {
+        return self::checksum($iban) === substr($iban, 2, 2);
+    }
+}

src/Faker/Provider/Payment.php

@@ -2,6 +2,7 @@
 
 namespace Faker\Provider;
 
+use Faker\Calculator\Iban;
 use Faker\Calculator\Luhn;
 
 class Payment extends Base
@@ -254,27 +255,7 @@ protected static function iban($countryCode, $prefix = '', $length = null)
 
         $result = static::addBankCodeChecksum($result, $countryCode);
 
-        $tempResult = str_split($result . $countryCode . '00');
-
-        // Convert letters to numbers
-        foreach ($tempResult as &$letter) {
-            $num = ord($letter) - 55;
-            if ($num >= 10 && $num <= 35) {
-                $letter = str_pad($num, 2, '0', STR_PAD_LEFT);
-            }
-        }
-        unset($letter);
-        $tempResult = join('', $tempResult);
-
-        // perform MOD97-10 checksum calculation
-        $checksum = (int) $tempResult[0];
-        for ($i = 1, $size = strlen($tempResult); $i < $size; $i++) {
-            $checksum = (10 * $checksum + (int) $tempResult[$i]) % 97;
-        }
-        $checksum = 98 - $checksum;
-        if ($checksum < 10) {
-            $checksum = '0'.$checksum;
-        }
+        $checksum = Iban::checksum($countryCode . '00' . $result);
 
         return $countryCode . $checksum . $result;
     }