PR feedback: Handle multiple active transactions gracefully

Handle cases with multiple active transactions by returning the most recent one
instead of throwing an IllegalStateException.

Author: goekay

src/main/java/de/rwth/idsg/steve/service/NotificationServiceForUser.java

@@ -27,7 +27,6 @@
 import de.rwth.idsg.steve.service.notification.OcppTransactionEnded;
 import de.rwth.idsg.steve.service.notification.OcppTransactionStarted;
 import de.rwth.idsg.steve.utils.TransactionStopServiceHelper;
-import de.rwth.idsg.steve.web.dto.UserQueryForm;
 import lombok.RequiredArgsConstructor;
 import lombok.extern.slf4j.Slf4j;
 import org.joda.time.DateTime;
@@ -57,7 +56,7 @@ public class NotificationServiceForUser {
     public void ocppStationStatusFailure(OcppStationStatusFailure event) {
         log.debug("Processing: {}", event);
 
-        var transaction = transactionService.getActiveTransaction(event.getChargeBoxId(), event.getConnectorId());
+        var transaction = transactionService.getLatestActiveTransaction(event.getChargeBoxId(), event.getConnectorId());
         if (transaction == null) {
             return;
         }
@@ -117,7 +116,7 @@ public void ocppTransactionStarted(OcppTransactionStarted event) {
     public void ocppStationStatusSuspendedEV(OcppStationStatusSuspendedEV event) {
         log.debug("Processing: {}", event);
 
-        var transaction = transactionService.getActiveTransaction(event.getChargeBoxId(), event.getConnectorId());
+        var transaction = transactionService.getLatestActiveTransaction(event.getChargeBoxId(), event.getConnectorId());
         if (transaction == null) {
             return;
         }

src/main/java/de/rwth/idsg/steve/service/TransactionService.java

@@ -80,7 +80,7 @@ public Transaction getTransaction(int transactionPk) {
         return transactionRepository.getTransactions(form).getFirst();
     }
 
-    public Transaction getActiveTransaction(String chargeBoxId, Integer connectorId) {
+    public Transaction getLatestActiveTransaction(String chargeBoxId, Integer connectorId) {
         TransactionQueryForm form = new TransactionQueryForm();
         form.setChargeBoxId(chargeBoxId);
         form.setConnectorId(connectorId);
@@ -93,7 +93,10 @@ public Transaction getActiveTransaction(String chargeBoxId, Integer connectorId)
         } else if (transactions.size() == 1) {
             return transactions.get(0);
         } else {
-            throw new IllegalStateException("There are multiple active transactions with the same charge box id and connector id");
+            log.warn("Found multiple active transactions for chargeBoxId '{}' and connectorId '{}'. Returning the most recent one.", chargeBoxId, connectorId);
+            return transactions.stream()
+                .max(Comparator.comparing(Transaction::getStartTimestamp))
+                .orElse(null); // Should not be null here, but for safety
         }
     }