Add ISR creditor reference validation

src/Z38/SwissPayment/TransactionInformation/ISRCreditTransfer.php

@@ -42,6 +42,10 @@ public function __construct($instructionId, $endToEndId, Money\Money $amount, IS
             ));
         }
 
+        if (self::modulo10(substr($creditorReference, 0, -1)) != (int) substr($creditorReference, -1)) {
+            throw new InvalidArgumentException('Invalid ISR creditor reference.');
+        }
+
         $this->instructionId = (string) $instructionId;
         $this->endToEndId = (string) $endToEndId;
         $this->amount = $amount;
@@ -109,4 +113,23 @@ public function setCreditorDetails($creditorName, PostalAddressInterface $credit
         $this->creditorName = $creditorName;
         $this->creditorAddress = $creditorAddress;
     }
+
+    /**
+     * Creates Modulo10 recursive check digit
+     *
+     * @param string $number Number to create recursive check digit off.
+     *
+     * @return int Recursive check digit.
+     */
+    private static function modulo10(string $number)
+    {
+        $moduloTable = [0, 9, 4, 6, 8, 2, 7, 1, 3, 5];
+
+        $next = 0;
+        for ($i = 0; $i < strlen($number); $i++) {
+            $next = $moduloTable[($next + intval(substr($number, $i, 1))) % 10];
+        }
+
+        return (int) (10 - $next) % 10;
+    }
 }

tests/Z38/SwissPayment/Tests/Message/CustomerCreditTransferTest.php

@@ -147,7 +147,7 @@ protected function buildMessage()
             'e2e-010',
             new Money\CHF(20000), // CHF 200.00
             new ISRParticipant('01-95106-8'),
-            '210000000003139471430009017'
+            '6019701803969733825'
         );
         $transaction12->setCreditorDetails(
             'Fritz Bischof',

tests/Z38/SwissPayment/Tests/TransactionInformation/ISRCreditTransferTest.php

@@ -28,6 +28,21 @@ public function testInvalidAmount()
         );
     }
 
+    /**
+     * @covers ::__construct
+     * @expectedException \InvalidArgumentException
+     */
+    public function testInvalidCreditorReference()
+    {
+        $transfer = new ISRCreditTransfer(
+            'id000',
+            'name',
+            new Money\CHF(100),
+            new ISRParticipant('01-25083-7'),
+            '120000000000234478943216891'
+        );
+    }
+
     /**
      * @covers ::setRemittanceInformation
      * @expectedException \LogicException
@@ -38,7 +53,7 @@ public function testSetRemittanceInformation()
             'id000',
             'name',
             new Money\CHF(100),
-            new ISRParticipant('10-2424-4'),
+            new ISRParticipant('01-25083-7'),
             '120000000000234478943216899'
         );