feat: Add 'fetch refund' request

src/Gateway.php

@@ -178,4 +178,13 @@ public function refund(array $parameters = [])
     {
         return $this->createRequest('\Omnipay\Square\Message\RefundRequest', $parameters);
     }
+
+    /**
+     * @param array $parameters
+     * @return \Omnipay\Common\Message\AbstractRequest|\Omnipay\Square\Message\FetchRefundResponse
+     */
+    public function fetchRefund(array $parameters = [])
+    {
+        return $this->createRequest('\Omnipay\Square\Message\FetchRefundRequest', $parameters);
+    }
 }

src/Message/FetchRefundRequest.php

@@ -0,0 +1,92 @@
+<?php
+
+namespace Omnipay\Square\Message;
+
+use Omnipay\Common\Message\AbstractRequest;
+use Omnipay\Common\Message\ResponseInterface;
+use Square\Environment;
+use Square\SquareClient;
+
+class FetchRefundRequest extends AbstractRequest
+{
+    public function getAccessToken()
+    {
+        return $this->getParameter('accessToken');
+    }
+
+    public function setAccessToken($value)
+    {
+        return $this->setParameter('accessToken', $value);
+    }
+
+    public function setRefundId($value)
+    {
+        return $this->setParameter('refundId', $value);
+    }
+
+    public function getRefundId()
+    {
+        return $this->getParameter('refundId');
+    }
+
+    public function getEnvironment()
+    {
+        return $this->getTestMode() === true ? Environment::SANDBOX : Environment::PRODUCTION;
+    }
+
+    private function getApiInstance()
+    {
+        $api_client = new SquareClient([
+            'accessToken' => $this->getAccessToken(),
+            'environment' => $this->getEnvironment()
+        ]);
+
+        return $api_client->getRefundsApi();
+    }
+
+    public function getData()
+    {
+        $data = [];
+
+        $data['refund_id'] = $this->getRefundId();
+
+        return $data;
+    }
+
+    public function sendData($data)
+    {
+        try {
+            $api_instance = $this->getApiInstance();
+
+            $result = $api_instance->getPaymentRefund($data['refund_id']);
+
+            if ($errors = $result->getErrors()) {
+                $response = [
+                    'status' => 'error',
+                    'code' => $errors[0]->getCode(),
+                    'detail' => $errors[0]->getDetail(),
+                    'field' => $errors[0]->getField(),
+                    'category' => $errors[0]->getCategory()
+                ];
+            } else {
+                $response = [
+                    'status' => 'success',
+                    'refund' => $result->getResult()->getRefund()
+                ];
+            }
+        } catch (\Exception $e) {
+            $response = [
+                'status' => 'error',
+                'detail' => 'Exception when retrieving refund: ' . $e->getMessage()
+            ];
+        }
+
+        return $this->createResponse($response);
+    }
+
+    public function createResponse($response)
+    {
+        return $this->response = new FetchRefundResponse($this, $response);
+    }
+
+}

src/Message/FetchRefundResponse.php

@@ -0,0 +1,33 @@
+<?php
+
+namespace Omnipay\Square\Message;
+
+use Omnipay\Common\Message\AbstractResponse;
+use Square\Models\PaymentRefund;
+
+class FetchRefundResponse extends AbstractResponse
+{
+    public function isSuccessful()
+    {
+        return $this->data['status'] === 'success';
+    }
+
+    public function getErrorDetail()
+    {
+        return $this->data['detail'];
+    }
+
+    public function getErrorCode()
+    {
+        return $this->data['code'];
+    }
+
+    public function getRefund(): ?PaymentRefund
+    {
+        if (!empty($this->data['refund'])) {
+            return $this->data['refund'];
+        }
+
+        return null;
+    }
+}