by Primsi: add and cleanup heper method copied from payment_datatrans module.

src/DatatransHelper.php

+<?php
+
+namespace Drupal\commerce_datatrans;
+
+use Drupal\Component\Utility\Crypt;
+use Drupal\Core\Site\Settings;
+use Drupal\payment\Entity\PaymentInterface;
+
+/**
+ * Helper methods for various Datatrans related tasks.
+ */
+class DatatransHelper {
+
+  /**
+   * Used for generation an internal key for validation purposes.
+   *
+   * @param PaymentInterface $payment
+   *   Payment Interface.
+   *
+   * @return string
+   *   The generated key.
+   */
+  public static function generateDatatransKey(PaymentInterface $payment) {
+    return Crypt::hashBase64($payment->id() . $payment->getPaymentStatus()
+        ->getPluginId() . Settings::getHashSalt() . \Drupal::service('private_key')
+        ->get());
+  }
+
+  /**
+   * Generates the server side sign to compare with the datatrans post data.
+   *
+   * @param string $hmac_key
+   *   The hmac key.
+   * @param string $merchant_id
+   *   Unique Merchant Identifier (assigned by Datatrans).
+   * @param string $amount
+   *   Transaction amount in cents or smallest available unit of the currency.
+   * @param string $currency
+   *   Transaction currency – ISO Character Code (CHF, USD, EUR etc.).
+   * @param string|int $transaction_reference
+   *   Our reference number.
+   *
+   * @return string
+   *   The computed hash.
+   */
+  public static function generateSign($hmac_key, $merchant_id, $amount, $currency, $transaction_reference) {
+    $hmac_data = $merchant_id . $amount . $currency . $transaction_reference;
+    return hash_hmac('md5', $hmac_data, pack('H*', $hmac_key));
+  }
+
+  /**
+   * Datatrans error code mapping.
+   *
+   * @param int $code
+   *   Provide error code from Datatrans callback.
+   *
+   * @return bool|FALSE|mixed|string
+   *   Returns error message.
+   */
+  public static function mapErrorCode($code) {
+    switch ($code) {
+      case '1001':
+        $message = t('Datrans transaction failed: missing required parameter.');
+        break;
+
+      case '1002':
+        $message = t('Datrans transaction failed: invalid parameter format.');
+        break;
+
+      case '1003':
+        $message = t('Datatrans transaction failed: value of parameter not found.');
+        break;
+
+      case '1004':
+      case '1400':
+        $message = t('Datatrans transaction failed: invalid card number.');
+        break;
+
+      case '1007':
+        $message = t('Datatrans transaction failed: access denied by sign control/parameter sign invalid.');
+        break;
+
+      case '1008':
+        $message = t('Datatrans transaction failed: merchant disabled by Datatrans.');
+        break;
+
+      case '1401':
+        $message = t('Datatrans transaction failed: invalid expiration date.');
+        break;
+
+      case '1402':
+      case '1404':
+        $message = t('Datatrans transaction failed: card expired or blocked.');
+        break;
+
+      case '1403':
+        $message = t('Datatrans transaction failed: transaction declined by card issuer.');
+        break;
+
+      case '1405':
+        $message = t('Datatrans transaction failed: amount exceeded.');
+        break;
+
+      case '3000':
+      case '3001':
+      case '3002':
+      case '3003':
+      case '3004':
+      case '3005':
+      case '3006':
+      case '3011':
+      case '3012':
+      case '3013':
+      case '3014':
+      case '3015':
+      case '3016':
+        $message = t('Datatrans transaction failed: denied by fraud management.');
+        break;
+
+      case '3031':
+        $message = t('Datatrans transaction failed: declined due to response code 02.');
+        break;
+
+      case '3041':
+        $message = t('Datatrans transaction failed: Declined due to post error/post URL check failed.');
+        break;
+
+      case '10412':
+        $message = t('Datatrans transaction failed: PayPal duplicate error.');
+        break;
+
+      case '-885':
+      case '-886':
+        $message = t('Datatrans transaction failed: CC-alias update/insert error.');
+        break;
+
+      case '-887':
+        $message = t('Datatrans transaction failed: CC-alias does not match with cardno.');
+        break;
+
+      case '-888':
+        $message = t('Datatrans transaction failed: CC-alias not found.');
+        break;
+
+      case '-900':
+        $message = t('Datatrans transaction failed: CC-alias service not enabled.');
+        break;
+
+      default:
+        $message = t('Datatrans transaction failed: undefined error.');
+        break;
+    }
+
+    return $message;
+  }
+}