Merge pull request #1 from BojanZelic/master

Added Refund support

src/AIMGateway.php

@@ -76,4 +76,9 @@ public function void(array $parameters = array())
     {
         return $this->createRequest('\Omnipay\AuthorizeNet\Message\AIMVoidRequest', $parameters);
     }
+
+    public function refund(array $parameters = array())
+    {
+      return $this->createRequest('\Omnipay\AuthorizeNet\Message\AIMRefundRequest', $parameters);
+    }
 }

src/Message/AIMRefundRequest.php

@@ -0,0 +1,24 @@
+<?php
+
+namespace Omnipay\AuthorizeNet\Message;
+
+/**
+ * Authorize.Net Refund Request
+ */
+class AIMRefundRequest extends AbstractRequest
+{
+  protected  $action = 'CREDIT';
+  public function getData()
+  {
+    $data = $this->getBaseData('RefundTransaction');
+
+    $this->validate('amount', 'transactionReference');
+
+    $data['x_trans_id'] = $this->getTransactionReference();
+    $data['x_card_num'] = $this->getCard()->getNumber();
+    $data['x_exp_date'] = $this->getCard()->getExpiryDate('my');
+    $data['x_amount']   = $this->getAmount();
+
+    return $data;
+  }
+}