src/main/java/de/zendric/app/xpensely_server/controller/ExpenseListController.java

@@ -19,6 +19,7 @@ import org.springframework.web.bind.annotation.RestController;
 
 import de.zendric.app.xpensely_server.model.AppUser;
 import de.zendric.app.xpensely_server.model.Expense;
+import de.zendric.app.xpensely_server.model.ExpenseInput;
 import de.zendric.app.xpensely_server.model.ExpenseList;
 import de.zendric.app.xpensely_server.model.InviteRequest;
 import de.zendric.app.xpensely_server.services.ExpenseListService;
@@ -95,9 +96,23 @@ class ExpenseListController {
     @PostMapping
     public ResponseEntity<ExpenseList> create(@RequestBody ExpenseList expenseList) {
         try {
-            ExpenseList savedItem = (ExpenseList) expenseListService.save(expenseList);
+            // Fetch or persist the `owner` AppUser
+            if (expenseList.getOwner() != null) {
+                AppUser existingOwner = userService.getUser(expenseList.getOwner().getId());
+                if (existingOwner == null) {
+                    throw new IllegalArgumentException("Owner does not exist.");
+                }
+                expenseList.setOwner(existingOwner);
+            } else {
+                throw new IllegalArgumentException("Owner is required.");
+            }
+
+            expenseList.setSharedWith(null);
+
+            ExpenseList savedItem = expenseListService.createList(expenseList);
             return new ResponseEntity<>(savedItem, HttpStatus.CREATED);
         } catch (Exception e) {
+            e.printStackTrace();
             return new ResponseEntity<>(null, HttpStatus.EXPECTATION_FAILED);
         }
     }
@@ -115,8 +130,11 @@ class ExpenseListController {
     @PostMapping("/{id}/add")
     public ResponseEntity<Expense> addExpenseToList(
             @PathVariable("id") Long expenseListId,
-            @RequestBody Expense expense) {
+            @RequestBody ExpenseInput expenseInput) {
         try {
+            AppUser expenseOwner = userService.getUserByName(expenseInput.getOwner());
+            Expense expense = expenseInput.convertToExpense(expenseOwner.getId());
+
             Expense addedExpense = expenseListService.addExpenseToList(expenseListId, expense);
             return new ResponseEntity<>(addedExpense, HttpStatus.CREATED);
         } catch (Exception e) {
@@ -153,6 +171,9 @@ class ExpenseListController {
         if (list.getSharedWith() != null) {
             return ResponseEntity.status(HttpStatus.IM_USED).body("List has already been shared");
         }
+        if (list.getOwner().getId() == inviteRequest.getUserId()) {
+            return ResponseEntity.status(HttpStatus.BAD_REQUEST).body("You cant join your own List");
+        }
         AppUser user = null;
         try {
             user = userService.getUser(inviteRequest.getUserId());

src/main/java/de/zendric/app/xpensely_server/model/ExpenseInput.java

@@ -0,0 +1,50 @@
+package de.zendric.app.xpensely_server.model;
+
+import java.time.LocalDate;
+
+import jakarta.persistence.GeneratedValue;
+import jakarta.persistence.GenerationType;
+import jakarta.persistence.Id;
+import lombok.AllArgsConstructor;
+import lombok.Getter;
+import lombok.NoArgsConstructor;
+import lombok.Setter;
+
+@Getter
+@Setter
+@AllArgsConstructor
+@NoArgsConstructor
+public class ExpenseInput {
+
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private Long id;
+
+    private String title;
+
+    private String owner;
+
+    private Double amount;
+    private Double deviation;
+
+    private LocalDate date;
+
+    private ExpenseList expenseList;
+
+    public Expense convertToExpense(Long userId) {
+        AppUser appUser = new AppUser();
+        appUser.setId(userId);
+        appUser.setUsername(owner);
+
+        Expense expense = new Expense();
+        expense.setAmount(amount);
+        expense.setDate(date);
+        expense.setDeviation(deviation);
+        expense.setExpenseList(expenseList);
+        expense.setId(id);
+        expense.setOwner(appUser);
+        expense.setTitle(title);
+
+        return expense;
+    }
+}

src/main/java/de/zendric/app/xpensely_server/services/ExpenseListService.java

@@ -98,15 +98,20 @@ public class ExpenseListService {
     }
 
     public Expense addExpenseToList(Long expenseListId, Expense expense) {
+        // find expenseList
         ExpenseList expenseList = repository.findById(expenseListId)
                 .orElseThrow(() -> new RuntimeException("ExpenseList not found with id: " + expenseListId));
+        // get all added expenses
         HashSet<Long> existingId = new HashSet<>();
         for (Expense e : expenseList.getExpenses()) {
             existingId.add(e.getId());
         }
+        // add the new expense
         expenseList.addExpense(expense);
+        // save
         repository.save(expenseList);
-        Expense newExpense = expense;
+
+        Expense newExpense = new Expense();
         for (Expense e : expenseList.getExpenses()) {
             if (!existingId.contains(e.getId())) {
                 newExpense = e;
@@ -137,14 +142,18 @@ public class ExpenseListService {
     public String generateInviteCode(Long listId) {
         ExpenseList list = repository.findById(listId)
                 .orElseThrow(() -> new RuntimeException("List not found"));
+        String inviteCode;
+        if (list.getInviteCode() == null || list.getInviteCodeExpiration().isBefore(LocalDateTime.now())) {
 
-        String inviteCode = UUID.randomUUID().toString().substring(0, 6).toUpperCase();
+            inviteCode = UUID.randomUUID().toString().substring(0, 6).toUpperCase();
             LocalDateTime expirationTime = LocalDateTime.now().plusWeeks(1);
 
             list.setInviteCode(inviteCode);
             list.setInviteCodeExpiration(expirationTime);
             repository.save(list);
-
+        } else {
+            inviteCode = list.getInviteCode();
+        }
         return inviteCode;
     }