Record a full refund correctly

CRM/Core/Payment/MJWIPNTrait.php

@@ -95,22 +95,23 @@ trait CRM_Core_Payment_MJWIPNTrait {
 
   /**
    * Record a refunded contribution
+   * This function ONLY supports full refunds
+   *
    * @param array $params
    *
    * @throws \CiviCRM_API3_Exception
    */
   protected function updateContributionRefund($params) {
-    $this->checkRequiredParams('updateContributionRefund', ['id', 'total_amount'], $params);
-
-    if ($params['total_amount'] > 0) {
-      $params['total_amount'] = -$params['total_amount'];
-    }
+    $this->checkRequiredParams('updateContributionRefund', ['id', 'payment_trxn_id'], $params);
 
     if (empty($params['cancel_date'])) {
       $params['cancel_date'] = date('YmdHis');
     }
+    $params['contribution_status_id'] = CRM_Core_PseudoConstant::getKey('CRM_Contribute_BAO_Contribution', 'contribution_status_id', 'Refunded');
 
     civicrm_api3('Contribution', 'create', $params);
+
+    $this->updatePaymentTrxnID($params['id'], $params['payment_trxn_id']);
   }
 
   /**
@@ -251,12 +252,17 @@ trait CRM_Core_Payment_MJWIPNTrait {
     // @fixme: There needs to be a better way to do this!!
     //   Contribution trxn_id = invoice_id, payment trxn_id = charge_id
     //   but calling completetransaction does not allow us to do that.
+    // @fixme: 2! Payment.get does not support the sort option so we can't do limit=1,sort=id DESC
     $payment = civicrm_api3('Payment', 'get', [
       'contribution_id' => $contributionID,
-      'options' => ['limit' => 1, 'sort' => "id DESC"],
     ]);
+    if (empty($payment['count'])) {
+      $this->exception('No payments found for contribution ID: ' . $contributionID);
+    }
+    krsort($payment['values']);
+    $paymentID = CRM_Utils_Array::first($payment['values'])['id'];
     civicrm_api3('FinancialTrxn', 'create', [
-      'id' => $payment['id'],
+      'id' => $paymentID,
       'trxn_id' => $trxnID,
     ]);
   }